Impact of Climate Change on Health in Africa: A Focus on Liver and Gastrointestinal Tract 3031394658, 9783031394652

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Amal Saad-Hussein Reda Elwakil Kenza Khomsi   Editors

Impact of Climate Change on Health in Africa A Focus on Liver and Gastrointestinal Tract

Impact of Climate Change on Health in Africa

Amal Saad-Hussein • Reda Elwakil • Kenza Khomsi Editors

Impact of Climate Change on Health in Africa A Focus on Liver and Gastrointestinal Tract

Editors Amal Saad-Hussein Department of Environmental & Occupational Medicine Environment & Climate Change Research Institute, National Research Centre Cairo, Egypt

Reda Elwakil Tropical Medicine Department Faculty of Medicine, Ain Shams University Cairo, Egypt

Kenza Khomsi Air Quality Department General Directorate of Meteorology Casablanca, Morocco

ISBN 978-3-031-39465-2 ISBN 978-3-031-39466-9 https://doi.org/10.1007/978-3-031-39466-9

(eBook)

© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Switzerland AG The registered company address is: Gewerbestrasse 11, 6330 Cham, Switzerland

Our concern to: Medical and non-medical scientists all over the word, and to the general population in low-income African countries who are mostly impacted by climate change.

Preface

This book reviews the current knowledge on how climate change impacts human health in African regions, with a special focus on diseases of the liver and the gastrointestinal tract (GIT). Medical experts from different regions of Africa discuss the effects of climate components as heat waves, droughts, floods, deforestation, and precipitation on human and animal movements, on food and water security, and the resultant spread of infectious agents such as viruses, parasites, and fungi. The book also provides an outlook on adaptive measures that could be taken to manage the emerging and re-emerging gastrointestinal and liver diseases as a result of climate change, besides highlighting the methods to mitigate the impact of climate change on the severity of these illnesses. The chapter titled “The Physical Basis for Climate Change” describes the basics of the science behind climate change and how climate change will affect temperature, rainfall, and storm events in Africa. The chapter titled “Current and Projected Climate Changes in Africa by Region” provides a comprehensive analysis of the current and projected impacts of climate change in the five sub-regions of Africa: Northern Africa, West Africa, Central Africa, East Africa, and Southern Africa. Each of these sub-regions faces unique climate challenges and is expected to experience rising temperatures, reductions in precipitation, and an increase in the frequency of heat waves. The chapter titled “Impacts of Climate Change on Environmental Toxins and Pollutants Causing Liver Health Problems” discusses the role of climate change on the environmental toxins and pollutants that may cause hepatotoxicity or carcinogenicity. While the chapter titled “Infectious Diseases and Change of Disease Pattern in Africa” presents an overview on the impact of different aspects of climate change on human and animal movements in the continent besides its impact on the distribution of microbiological hepatic and GIT diseases, the chapter titled “Impact of Climate Change on Viral Diseases in Africa” addresses specifically the impact of climate change on the prevalence of viruses affecting the liver and GIT in different regions of the African continent with focus on arboviruses, hepatitis A virus, and hepatitis E virus besides hepatitis B and C viruses. The chapter titled

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“Impact of Climate Change on Parasitic Diseases in Africa” gives a detailed presentation of different parasitic diseases in Africa and how climate change impacts these diseases. The chapter titled “Impact of Migration on GIT Illness in Africa” discusses the impact of climate migration on the increasing prevalence of the liver and gut diseases. This occurs due to the spread of diseases to new areas and living conditions in refugees camps characterized by tight socioeconomic circumstances. Additionally, the chapter discusses the impact of a large number of migrants on socioeconomic unrest and its effects on health in general and on liver and gut health in particular. The chapter titled “Water Security and Its Impact on the Liver and Gut Health in Africa” discusses the relation between rainfall in Africa, whether increase or decrease, and health in general including kidney diseases, skin diseases, mental health, etc. with focus on the liver and gut health in particular. The chapter titled “Food Security in Africa and Its Impact on the Liver and Gut Health” discusses the impact of climate change on the food health problems, whether undernutrition or overnutrition, in different African regions. The chapter titled “Towards African National and Regional Plans for Adaptation and Mitigation” gives an overview on the mitigation and adaptation strategies planned to be implemented in the different sectors in Africa. There is a great gap in climate change research funding in Africa compared to the rest of the world. This chapter highlights the most important gaps and addresses the ways to solve this problem. Cairo, Egypt Cairo, Egypt Casablanca, Morocco

Amal Saad-Hussein Reda Elwakil Kenza Khomsi

Contents

The Physical Basis for Climate Change . . . . . . . . . . . . . . . . . . . . . . . . . Desmond Leddin

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Current and Projected Climate Changes in African Subregions . . . . . . . Kenza Khomsi, Reda El Wakil, Chukwuemeka Onyekachi Nwaigwe, Mohau Mateyisi, and Shingirai Shepard Nangombe

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Impacts of Climate Change on Environmental Toxins and Pollutants Causing Liver Health Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Amal Saad-Hussein and Haidi Karam-Allah Ramadan

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Infectious Diseases and Change of Disease Pattern in Africa . . . . . . . . . Ashraf Albareedy and Haidi Karam-Allah Ramadan

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Impact of Climate Change on Viral Disease Burden in Africa . . . . . . . . Reda Elwakil, Gamal Esmat, Yasser Fouad, and Mohamed Bassam

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Impact of Climate Change on the Liver and GIT Parasitic Diseases . . . . 119 Reda Elwakil Impact of Migration on Gastrointestinal and Liver Diseases in Africa . . 153 C. Wendy Spearman, Haidi Karam-Allah Ramadan, Mark Sonderup, and Amal Saad-Hussein Water Security and Its Impact on the Liver and Gut Health in Africa . . 195 Ashraf Albareedy Climate Change Impacts on Nutrition . . . . . . . . . . . . . . . . . . . . . . . . . . 215 Mona Adel Helmy Towards African National and Regional Plans for Adaptation and Mitigation of the Impact of Climate Change: Focus on the Liver and Gut Health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 Amal Saad-Hussein, Reda Elwakil, and Samah Ait Benichou ix

About the Editors

Amal Saad-Hussein (Corresponding editor) is Emeritus Professor of Environmental and Preventive Health in the Department of Environmental & Occupational Medicine at the Institute of Environment & Climate Change Research, National Research Centre, Egypt. She obtained her master’s and MD degrees in Public Health and Environmental Medicine from the Faculty of Medicine, Cairo University. She was former Dean of Environment and Climate Change Research Institute (2016–2020) and former Head of Environmental and Occupational Medicine Department (2011–2016), National Research Centre (NRC), Egypt. She is a member of Climate Change National Committee, National Committee of Toxicology, and the Environmental Research Council. She is an expert and reviewer at WGII-IPCC and an internal expert in the Central Administration of Climate Change, EEAA. She obtained several scientific prizes: Technological Creation Prize (2006), Prize of Environmental Research and Environmental Education (2007), and the Certificates of Excellence in Scientific Productions for years 2009–2015. She published around 81 international and 21 national publications, and she was the principal investigator of several national projects funded by ASRT, STDF, and NRC, in the field of environmental health impacts and design strategies for prevention and control. Reda Elwakil (Co-editor) is Emeritus Professor of Tropical Medicine in the Faculty of Medicine at Ain Shams University, Egypt. Prof. Reda Elwakil had his MD degree in Tropical Medicine and Hygiene from the Tropical Medicine Department, Ain Shams University 1986. He worked actively in the same department, engaging in teaching, training, clinical practice, and research in the fields of tropical medicine, gastroenterology, hepatology, infectious diseases, and endoscopy since 1981. Currently, he is the permanent secretary of the African Middle East Association of Gastroenterology (AMAGE). He is a member of Climate Change and

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Clinical Research Committees in the WGO. He established the African Climate Group in AMAGE. Prof Elwakil worked as a guest editor for a special topic in Frontiers in Medicine “Global Excellence in Gastroenterology Practice: Africa” in 2022. He is the author of several papers published in peer-reviewed international journals in hepatology, gastroenterology, endoscopy, and climate change. Kenza Khomsi (Co-editor) is Associate Professor at Mohamed VI University for Health Sciences, Morocco. Kenza Khomsi is a climate and air quality expert focusing on the impact of air quality on health and its relationship with atmospheric circulation. She is a member of the International Society of Environmental Epidemiology and holds the position of Deputy Chair for the Eastern Mediterranean chapter. Kenza also contributes to the World Health Organization’s Global Air Pollution Technical Advisory Group. She has served as a coordinating lead author for the Africa integrated assessment of air pollution and climate change led by the Climate and Clean Air Coalition. With a background including a PhD in Environmental Epidemiology and a PhD in Climatology, a Master’s in Theoretical and Applied Mechanics, and an engineering degree in Meteorology, Kenza’s expertise extends across various domains. Additionally, she is a certified coach (ICF-PCC), mentor, and trainer, integrating coaching methodologies into scientific research.

The Physical Basis for Climate Change Desmond Leddin

Abstract The purpose of this chapter is to review the scientific background to the issue of global warming and climate change. This chapter starts by presenting the history of atmospheric science and the basis of how greenhouse gases (GHGs) contribute to atmospheric warming. It is important to understand the sources of greenhouse gases, their mechanism of action, relative contributions to warming, and the contributions of different countries to the problem to help the global efforts in mitigation and adaptation of the impacts of climate change. Future projections for climate including temperature, precipitation, drought, and extreme weather events such as cyclones are addressed. This chapter explains briefly the computer-based models used to study the projected climate changes in different scenarios in different regions of the world. Global initiatives to reduce greenhouse gases will be discussed. At present, it is not clear whether that effort will be sufficient to keep global mean surface temperature (GMST) below 2 °C by the end of the century as set under the Paris Agreement. Given that expectation, it is important that countries begin to adapt to the new climate realities and prepare for the changes that are coming. This is especially important in Africa where a significant vulnerable population will face increasing challenges of changes in temperature, precipitation, and access to water and nutrition, which impact the infrastructure and the socioeconomic stability of vulnerable countries. Keywords Climate change · Africa · Global warming · Precipitation · Drought · Extreme weather events · Climate change models

D. Leddin (✉) Department of Medicine, Dalhousie University, Halifax, NS, Canada e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 A. Saad-Hussein et al. (eds.), Impact of Climate Change on Health in Africa, https://doi.org/10.1007/978-3-031-39466-9_1

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Abbreviations AR6 COP EPA GHG GWP IPCC NDC PPM RCP SSP UK UNFCCC

Assessment Report 6 Conference of the Parties Environmental Protection Agency Greenhouse gases Global warming potential Intergovernmental Panel on Climate Change Nationally determined contributions Parts per million Representative concentration pathways Shared socioeconomic pathways United Kingdom United Nations Framework Convention on Climate Change

1 Introduction The purpose of this chapter is to review the scientific background to the issue of global warming and climate change. The history of atmospheric science and the recognition of how greenhouse gases contribute to atmospheric warming will be briefly reviewed. It is important to understand the sources of greenhouse gases, their mechanism of action, relative contributions to warming, and the contributions of different countries to the problem. The response to the threat will be discussed as will the projections for future warming and the consequences that will ensue.

2 Historical Background The atmosphere that surrounds the Earth is of fundamental importance to life on the planet. Changes in the atmosphere as evidenced by changes in weather, precipitation, and temperature affect our daily life and our ability to access the basic necessities of shelter, water, and nutrition. Evidence of attempts to understand changes in the atmosphere goes back as far as recorded history. Both the ancient Egyptian and Greek scholars attempted to study, understand, and predict atmospheric conditions (Zinezer 1944; Clark 2022). In more modern times, the work of the French scientist Joseph Fourier (1768–1830) is foundational to understanding the role of the atmosphere in global warming. Fourier calculated that the earth, given its distance from the sun, should be much colder than it is and postulated that the atmosphere was acting as an insulator. In the mid-nineteenth century, as the understanding of geology continued to advance, there was a considerable interest in how glaciers advanced and retreated. Driven in

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part by a desire to understand that cycle, the American amateur scientist Eunice Foote and the Irish scientist John Tyndall studied the role of different gases in producing the insulating effect of the atmosphere. In 1896, the Swedish scientist Svante Arrhenius published his work on the mathematics of atmospheric warming and the role that carbon dioxide (CO2) might play (Arrhenius 1896). Although both Foote and Arrhenius clearly pointed out the potential for increased atmospheric carbon dioxide to increase global temperature, this was not perceived as a threat. It was thought that a warming climate would lead to a greater opportunity to grow crops and would generally be a positive effect. Weart (2004) described how gradually through the twentieth century came the realization that atmospheric warming could have negative consequences. This came prominently to public consciousness with the testimony of the scientist James Hansen to Congress in 1988. Hansen’s testimony was based in part on the data and measurement of carbon dioxide in the atmosphere from the laboratory of Charles Keeling (1928–2005). Keeling had established the laboratory at the summit of an extinct volcano in Hawaii. He showed that carbon dioxide levels were rising inexorably over the time span of his measurement. In the same year as Hansen’s presentation, the United Nations established the Intergovernmental Panel on Climate Change (IPCC), which has become a major force in bringing science of climate change to both public and politicians. The industrial revolution began in the mid-eighteenth century. It was characterized by a switch in manufacturing processes from hand production to machine production. It began first in the United Kingdom and Europe and somewhat later in the United States. Some countries have only industrialized in relatively recent times. The switch to machine manufacturing requires energy. Initially, some of this was provided by waterpower, but later it depended on the combustion of fossil fuels, particularly coal, oil, and gas. Coal has been mined in ancient times in China and during the Roman Empire. However, this was on a small scale, and it was only with the advent of the industrial revolution that coal mining could be and was carried out in industrial quantities. Mining of coal, a very potent source of greenhouse gases and aerosol emissions, continues to the present. Some of the world’s greatest producers and consumers of coal are among those countries with the highest greenhouse gas emissions per capita. Coal is an important source both of energy and of greenhouse gas emissions and pollution. The history of the oil industry is similar. Oil extraction did exist in China over 1500 years ago, but it was only in the mid-nineteenth century that commercial development really expanded. Oil overtook coal as the world’s main source of energy from the mid-1900s on.

3 Greenhouse Gases How do they cause warming? When solar radiation strikes the surface of the earth, or the atmosphere, some is reflected but most is absorbed and causes heating. The heat is reflected from the surface of the warmed earth and atmosphere in the infrared

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Fig. 1 The greenhouse effect. (Source: US EPA 2012)

spectrum, a different wavelength to that of the solar energy coming in. Infrared radiation travels at a wavelength of 700–1,000,000 nm. Oxygen and nitrogen do not absorb radiation at this wavelength, but some atmospheric gases such as carbon dioxide do. This leads to increased kinetic energy of the molecules in these gases, which effectively then act as storage for heat that would otherwise be lost into space (Fecht 2021). Although this is described as the greenhouse effect, it is not how greenhouses warm air. Greenhouses work by trapping heated air that is not allowed to move away by convection and other forces (Fig. 1).

4 Origins and Impacts The main greenhouse gases in the earth’s atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Although water molecules persist in the atmosphere for a very short duration, they are an important source of warming and an example of a positive feedback loop. Warmer temperatures cause more evaporation of water from the surface of the earth and oceans, and this leads to further warming of the atmosphere. The gases differ in their origins, the degree to which they contribute to warming and in their duration of action in the atmosphere. The relative contribution, the global warming potential (GWP), of each gas is calculated relative to that of carbon dioxide, which is given a reference value of 1 as mentioned in the Environmental

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Protection Agency (EPA) website (https://www.epa.gov/ghgemissions/understand ing-global-warming-potentials). The following is from an overview of greenhouse gases (EPA n.d-a). Carbon dioxide is the most abundant greenhouse gas comprising about 80% of greenhouse gas emissions in the United States. It is released into the atmosphere primarily through burning of fossil fuels such as coal, natural gas oil, and gasoline. It can also be generated by burning solid waste, wood, and other biological materials including biofuels. Significant amounts are released through the production of cement and other chemical reactions. Carbon dioxide undergoes a carbon cycle. When it is released into the atmosphere, it is absorbed by the oceans, soil, and plants; incorporated into organic materials; and released again (EPA n.d-b). Methane, which comprises about 10% of the US emissions, is present in much smaller amounts than carbon dioxide but is much more potent as a greenhouse gas. It has a GWP of 28–36. Methane lasts for a much shorter period in the atmosphere than carbon dioxide but because of its molecular structure it can absorb more reflected infrared energy. The primary sources of methane are the fossil fuel industries as considerable amounts of methane are leaked during the production of natural gas and during the production and transport of coal and oil. Cattle are also an important source as ruminants belch methane into the atmosphere as part of their digestive process. Methane also arises from the decay of organic matter, which can be naturally occurring or can occur from landfills. Nitrous oxide, 3% of emissions, has a GWP of 265–298 times that of carbon dioxide. This gas can be generated by the combustion of fossil fuels and solid waste and during the treatment of wastewater. Agricultural land use and industrial activities contribute significant amounts. Chlorofluorocarbons, hydrofluorocarbons, hydrochlorofluorocarbons, perfluorocarbons, and sulfur hexafluoride, although present in small amounts (3%), are much more powerful than any of the other gases with GWPs of thousands to tens of thousands. They are emitted from a variety of industrial processes. Fluorinated gases are sometimes used as substitutes for ozone-depleting chemicals. Some anesthetic gases are chlorofluorocarbons and a significant contributor to atmospheric warming (Charlesworth and Swinton 2017). Ozone is technically a greenhouse gas but is often not considered as such. Its role in global warming and environmental protection is complex depending on its concentrations of different levels of the atmosphere. In the troposphere, where humans live, it can be injurious to health. Ozone is created by a chemical reaction between sunlight, nitrogen oxides, and volatile organic compounds. The main sources are emissions from cars, power plants, and industrial and commercial activities. In the stratosphere, it prevents harmful ultraviolet radiation from reaching the surface of the earth and is a benefit to humans and plants.

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5 Global Production and National Contributions Historical measurements of carbon dioxide are available from ice core measurements and from current real-time monitoring. Over the last several hundred thousand years, carbon dioxide levels have fluctuated but have never exceeded 300 parts per million (ppm) until the onset of industrialization. Atmospheric carbon dioxide concentrations are now higher than at any time in at least two million years, and concentrations of methane and nitrous oxide are higher than at any time in the last 800,000 years (IPCC AR6 WGI SPM A 2.1 n.d.). Once coal, and later oil, began to be used as an energy source, carbon dioxide levels began to rise very quickly and now exceed 415 ppm. The onset of industrialization also coincided with rapid increases in human populations. The combination of rising numbers of people utilizing increasing amounts of fossil fuels to drive economic growth has led to the increase in atmospheric carbon, which is now seen. In 1922, total global carbon dioxide emissions were 3.23 billion tonnes. The current production of carbon dioxide is over 36 billion tonnes (Our World in Data n.d.-b), and total GHG approximates 50 billion tonnes per year of CO2 equivalents. In the last 100 years, there has been an increase in emissions of over 1500%.

6 Sources of Emissions Energy production accounts for nearly three quarters of global greenhouse gas emissions. Given the central role of fossil fuels in the global economy, this is not surprising. This includes energy used in buildings (17.5%), transportation (16.2%), and industry (24.2%). Agriculture, forestry, and land use contribute 18.4%, waste 3.2%, and industrial processes involved in chemical and cement manufacturing 3%. The type of greenhouse gas produced varies by economic sector. For example, fugitive emissions from energy production account for nearly 6% of greenhouse gases. The greenhouse gas in this case is predominantly methane. Cement and steel are essential building materials and are a particular concern. It has been estimated that cement contributes 2,300,000,000 tonnes of carbon dioxide per year to global emissions. Making iron and steel contributes 2,600,000,000 tonnes (Fennell et al. 2022) (Fig. 2). Knowing the origin of the gases within each sector is important for mitigation efforts. Within the agricultural sector, for example, cattle are the leading producer of greenhouse gases. They produce up to hundred kilograms of methane per year. This has led to calls to move away from a meat-based diet toward one higher in vegetables and associated with lower emissions.

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Fig. 2 Global greenhouse gas emissions by sector. (Source: Our World in Data n.d.-a. OurWorldinData.Org – Research and data to make progress against the world’s largest problems. Source: Climate Watch, the World Resources Institute (2020). Licensed under CC-BY by the author Hannah Ritchie 2020)

7 Health Sector Contributions The National Health Service in the United Kingdom has published an analysis of its carbon footprint (Tennison et al. 2021). The largest single component in the UK health system is the supply chain and the goods and services required to deliver the service. Pharmaceuticals and chemicals are the largest components of this with medical equipment and business services coming in close behind. Delivery of care requiring use of building energy, and generating waste, and business travel are the next largest sectors followed by personal travel, which includes patients, staff, and visitors.

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8 Which Countries Contribute the Most? There are differences between continents with regard to CO2 production. The most is produced in Asia with North America and Europe also producing large amounts. Africa, one of the continents that are most likely to suffer from climate change, produces relatively little, as does South America and Oceania (Fig. 3). Countries with large populations and a large industrial base are the greatest contributors. In absolute terms of emissions per country, the pattern is somewhat different. China, because of its large population and rapid industrialization, is the world’s largest emitter of greenhouse gases with annual CO2 emissions from fossil

Fig. 3 Carbon dioxide emissions by continent and country. The size of the block is proportional to the amount of emissions. (Source: Our World in Data n.d.-c. Shown are national production-based emissions in 2017. Production-based emissions measure CO2 produced domestically from fossil fuel combustion and cement, and do not adjust for emissions embedded in trade (i.e. consumptionbased). Figures for the 28 countries in the European Union have been grouped as the ‘EU-28’ since international targets and negotiations are typically set as a collaborative target between EU countries. Values may not sum to 100% due to rounding. Data Source: Global Carbon Project (GCP). This is a visualization from OurWorldinData.org. where you find data and research on how the world is changing. Licensed under CC-BY by the author Hannah Ritchie)

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fuels of around ten billion tonnes. The United States is just about a half of this at 5.26 billion tonnes, and the 27 European Union states reduce 2.91 billion tonnes. India, again because of its large population and rising industrialization, is a significant contributor at 2.63 billion tonnes. In per capita terms, in 2019, the average emissions in the world were 4.76 tonnes. Australia (16.45 tonnes per person), the United States (15.97 tonnes), and Canada (15.57 tonnes) are the world’s largest emitters significantly exceeding those of China at 7.32 tonnes per person and even those of the industrialized United Kingdom at 5.46 tonnes per person.

9 Pollution Pollution is the introduction into the environment of substances that cause damage to the human or natural environment. Pollutants can be naturally occurring or synthetic and be composed of solid, liquid, gas, or simply energy such as light and radiation. Pollutants can affect humans and the environment either directly or indirectly. Some pollutants are directly toxic, and others act by affecting water and air quality or enter the food chain. Pollution and climate change interact in several ways. The same factors that drive global warming and climate change also contribute to pollution of the environment. Combustion of fossil fuels, one of the main drivers of global warming, by cars is a very significant contributor to air pollution and climate warming. Another example is the relationship between climate change and wildfires. Climate change may lead to an increase in the number of wildfires. Wildfires, in turn, release significant pollutants into the atmosphere. Furthermore, the chemicals used to stop wildfires can get into the water reservoirs and pollute rivers and soil. In the context of climate change, much attention is focused on the role that aerosols might play in global warming or cooling. Aerosols in the atmosphere can be suspensions of liquid, solid, or mixed particles (Myhre et al. 2013). They vary in chemical composition and size (Putaud et al. 2010). They can be either primary aerosol, those released into the atmosphere, or secondary aerosol, those produced in the atmosphere from precursor gases. Primary aerosols can be organic or inorganic. Some aerosols can absorb solar radiation and contribute to global warming. Black carbon is the most important of these. Others can scatter solar radiation and have a cooling effect. Since burning of fossil fuels is an important source of aerosols, a reduction in aerosol concentration in the atmosphere, as attempts are made to reduce fossil fuel consumption, may paradoxically remove the beneficial cooling effect of these aerosols.

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Biodiversity

Biodiversity can be defined as the biological variety and variability of life on the earth. Biodiversity is essential for healthy human and planetary systems (Cardinale et al. 2012) including food production, water cleansing, and prevention of zoonoses. Biodiversity loss is related to climate change and pollution in that some of the same factors that are contributing to climate change and damage to the environment can also cause loss of biodiversity. For example, deforestation of the Amazon results in a shrinking habitat for plants and animals. The land that is cleared may be used for rearing cattle, which in turn are a significant source of greenhouse gases. Similarly, the reef systems of the oceans, an important source of marine biodiversity, are vulnerable to changes in both the temperature and acidity. A lack of biodiversity may decrease the stability and productivity of ecosystems and increase vulnerability to infections that can affect humans, animals, and flora.

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The Response to the Climate Crisis

The Intergovernmental Panel on Climate Change (IPCC) was established by the World Meteorological Organization and the United Nations in 1988 (IPCC; https:// www.ipcc.ch). The mission of the IPCC is to produce reports on the natural, political, and economic impacts and risks and possible responses based on ongoing surveys of the world’s literature. The IPCC does not conduct original research, but it does facilitate original work by bringing together hundreds of scientists. Three working groups contribute to each of the IPCC reports, which are now in the sixth cycle. Working Group 1 deals with the physical science basis; Working Group II deals with impacts, adaptation, and vulnerability; and Working Group III deals with the mitigation of climate change. The IPCC reports are an invaluable synthesis of current understanding of the challenge of climate change. The United Nations Framework Convention on Climate Change (UNFCCC) entered into force in 1994. The goal of the treaty is to stabilize greenhouse gas concentrations. It arose in part from the Rio conventions in 1992 (United Nations Climate Change; https://unfccc.int). The UNFCCC was responsible for the Kyoto Protocol that was superseded by the Paris Agreement in 2016. The goal of the Paris Agreement was to keep global warming to below 2 °C by 2100. In order to meet that target, countries need to cut their greenhouse gas emissions. Each country has been asked to draw up nationally determined contributions (NDCs). The NDCs (Nationally Determined Contributions; United Nations Climate Change; https://unfccc.int) are nonbinding goals set by each country to mitigate climate emissions. The hope is that countries will cooperate globally to reduce emissions and limit atmospheric warming. Parties to the UNFCCC meet yearly at a Conference of the Parties (COP) to assess the progress toward meeting the goals of the convention.

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Two issues arise. The first is whether the indices are sufficient to meet the target of the Paris Agreement, and the second is whether countries are meeting their targets. In a recent analysis, it has been found that the probability of the United States reaching its NDC was only 2% and it was 16% for China. Even if, as seems unlikely, countries do meet their NDCs, there is no certainty that atmospheric warming will stay under 2 °C. Based on the current trends, it has been reported that the probability of staying below 2 °C is only 5% (Liu and Raftery 2021). It is likely that by 2100 global mean surface temperature will exceed 2 °C.

11.1

Where Are We Now?

In October 2021, the IPCC Working Group I produced Assessment Report 6 (AR6) on the basis of physical science for climate change (IPCC 2021). The report stated that it was unequivocal that human influence has warmed the atmosphere, ocean, and land. This was an important development. Previously, the slight uncertainty as to the relative contributions of natural and human factors had allowed a basis for inaction on the part of some individuals and countries.

Fig. 4 Changes in global surface temperature since 1850. (Source: Our World in Data. https:// ourworldindata.org/co2-and-other-greenhouse-gas-emissions. Source: Hadley Centre (HadCRUT4). OurWorldInData.org/co2-and-other-greenhouse-gas-emisions. CC BY. Note: The red line represents the median average temperature change, and grey lines represent the upper and lower 95% confidence intervals)

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As shown in Fig. 4, the world is now warmer than it has been anytime in the last 200 years. The rise in the temperature is unprecedented. While it is true that the world has been warmer than this previously, this has not occurred when humans inhabited the earth. Almost all, if not all, of the rising global mean surface temperature is due to human factors. The world has already warmed by over 1 °C compared with the preindustrial times (IPCC 2021). A rise in global mean surface temperature has already resulted in changes in multiple interlinked systems. A warmer atmosphere can hold more water and contains more energy. AR6 concluded that human-induced climate change is already affecting weather extremes in every region across the globe (IPCC 2022). This is manifested by changes in climate extremes such as heat waves, heavy rainfall events, droughts, and tropical cyclones. The IPCC reported that heat extremes including heat waves have become more frequent and more intense, while cold extremes become less frequent and less severe. A decrease in cold extremes may seem like a benefit but that may not necessarily be so. Cold temperatures are important in controlling potential human and plant pathogens. Consistent with the observation that a warmer atmosphere holds more water, the frequency and intensity of heavy precipitation events have increased since the 1950s over the most land areas. It was previously recognized that the intensity of storms has increased, but there is less certainty that the frequency may have increased. Compound events are those in which several climate hazards combine (Zscheischler et al. 2018a, b). For example, drought associated with high heat may lead to wildfires and increased air pollution (Zscheischler et al. 2018a, b). The IPCC also reported that climate change has likely increased the chance of compound extreme events (IPCC 2022).

11.2

What Will Happen? Predicting the Future

Experiments cannot be carried out on the planet, so models are needed. Datasets allow different groups to have a common starting point for inputs into climate models. Perturbations can be introduced, and effects can be seen. Modelling changes in global temperature and the resulting climate over a period of decades are extraordinarily complex. It was not really possible before the advent of powerful computers. Even with modern computing technology, it remains a challenge. In order to facilitate the modelling process, datasets called Representative Concentration Pathways (RCPs) have been developed, which can be used to prime-modelling data (van Vuuren et al. 2011). RCPs were introduced beginning with IPCC Assessment Report 5. Variables such as population, land use, energy intensity, energy use, and regional differential development were incorporated. Pathways were described based on the amount of change in radiative forcing by 2100. Radiative forcing is defined as the difference between the sunlight radiant energy received by the earth and the energy radiated back to space. RCP2.6 represents a peak in radiative forcing at approximately 3 W/m2 during the

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mid-century before declining to 2.6 W/m2 by 2100. RCP4.5 represents stabilization (without overshoot) in radiative forcing at 4.5 W/m2 post-2100. RCP6.0 represents stabilization (without overshoot) in radiative forcing at 6 W/m2 post-2100. RCP8.5 represents a rise in radiative forcing to 8.5 W/m2 in 2100. RCP8.5 is often referred to as the business-as-usual scenario. It is the likely outcome if difficult, and immediate, mitigation efforts are not taken (RCPs n.d.). Assessment Report 6 introduced Shared Socioeconomic Pathways (SSPs) (O’Neill et al. 2014). Socioeconomic narratives were not included in the RCPs, but the SSPs are based on five potential socioeconomic trends: SSP1, a world of sustainability-focused growth and equality; SSP2, a world where trends broadly follow their historical patterns; SSP3, a fragmented world of “resurgent nationalism”; SSP4, a world of ever-increasing inequality; and SSP5, a world of a rapid and an unconstrained growth in economic output and energy use (Carbon brief n.d.). As with RCP modelling, these new pathways include scenarios with high and very high greenhouse gas emissions, scenarios with intermediate greenhouse gas emissions, and scenarios with very low and low greenhouse gas emissions.

11.3

Consequences of Atmospheric Warming

The essential problem is a net positive increase in atmospheric energy due to the effect of greenhouse gases in the atmosphere. The primary effect of this energy is to increase atmospheric and global mean surface temperature. AR6 has modelled the temperature changes that may be seen with different climate scenarios varying from low-emission scenarios to high-emission scenarios.

11.3.1

Temperature

AR6 reported (IPCC 2022: AR6. SPM WGII B1.1. Table SPM 1) that global surface temperature will continue to increase until at least the mid-century under all the emission scenarios. In the near term, under all scenarios, the best estimate of temperature rise is 1.5 °C. Beyond 2040, however, temperature estimates begin to diverge based on the amount of net energy being retained in the atmosphere. Under the best case scenarios, temperature may reach 1.6 °C, but at the other end of the scale, with a high-emission scenario, it may reach as much as 2.4 °C. This divergence is even more marked from 2081 on. In the long term, under a low-emission scenario, temperature rise may be held at 1.4 °C, but under a highemission scenario, it will reach as much as 4.4 °C, with a very likely range of up to 5.7 °C. The data emphasize the fact that we are in the critical decades with regard to controlling the magnitude of the rise of atmospheric temperature. Increased temperature in the atmosphere affects wind patterns, the distribution of the amount of precipitation, the frequency and severity of storms, the frequency and

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intensity of high temperature events, the number of frost-free days, the temperature of the oceans, and melting of ice and permafrost. When these changes are presented as averages, it is easy to lose the impact of extremes or of increasing variability in climate. For example, the average precipitation in an area may remain constant, but that is not helpful if the rain does not appear at the right time for planting or nurturing crops. A long period of drought followed by torrential rain may, on average, produce a normal amount of rainfall over the course of 12 months, but in fact it may be very destructive. AR6 also reported that many changes in the climate system will become magnified in direct relation to an increase in global warming. Increases in the frequency and intensity of heat extremes, marine heat waves, heavy precipitation, in some regions drought, an increase in intense tropical cyclones, and reduction in Arctic ice and permafrost can all be expected (IPCC 2022: AR6 SPM WGII B2). It is also anticipated that there will be increased variability of the global warming, water cycle, global monsoon precipitation, and severity of wet and dry events. Thus far, the oceans have helped modulate the rise in atmospheric carbon and the rise in atmospheric temperature, but there are signs that the ability of the oceans to do this is beginning to be exhausted.

11.3.2

Oceans

Over 70% of the world’s surface area is covered by oceans. Oceans contain 97% of the earth’s water. An additional 10% of the earth’s surface is covered by glaciers and ice sheets. The IPCC has produced a special report on the oceans and cryosphere. The oceans play a critical role in climate control but are also important as a source of food and for trade, transport, and habitat. The IPCC estimated that by mid-century over one billion people will be living in low-lying coastal zones and potentially impacted by rising oceans and storm surges. The loss of ice sheets and glaciers is one of the more public faces of global warming. It is an image which the public is familiar with. There is a high, or a very high, level of confidence that these changes are widespread and increasing. Many populations depend on runoff from glaciers as a source of freshwater. As glacial supply of freshwater decreases, these populations will be at a significant risk of water insecurity. Permafrost temperatures have increased to record high levels. In addition to the ecosystem changes that this will produce, the loss of permafrost opens up the possibility of very large releases of methane and other greenhouse gases that are sequestered in higher latitudes. The IPCC has also concluded that it is virtually certain that the ocean has warmed. Up to this point, the oceans have absorbed more than 90% of the excess heat in the climate system. That has been at the cost of increased acidification and the decrease in oxygen content. Both of these have significant implications for marine biology and for food production. The IPCC can say with medium confidence that this is

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already affecting the maximum catch potential. This has significant implications for nutrition especially in the tropics for which the effects may be most marked. Sea level changes are already occurring. Global mean sea level increased by 20 cm between 1901 and 2018. This is due in part to thermal expansion of the oceans as water absorbs heat and also due to melting of polar and Greenland ice sheets. Given that nearly 1,000,000 people will be living close to the ocean edge by mid-century, this is clearly a major concern. Small island nations of the Pacific are already under threat from a combination of rising sea levels and increased severity of storms. It can be anticipated that population displacement of millions of people will occur as a result of rising sea levels.

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Regional Differences

The IPCC has published global maps of the change in temperature and precipitation by region. The IPCC AR6 Working Group 1 has developed an interactive atlas to allow the visualization of change by region (https://interactive-atlas.ipcc.ch). Regarding temperature, as GMST reaches 1.5 °C, changes are seen in all land areas. Temperature rise will be most marked in the northern latitudes and least over southern South America. The Arctic and sub-Arctic areas are most impacted. Initially, the oceans are less affected due to their ability to buffer temperature rise. As the temperature reaches a mean global change of 2.0 °C, the changes in the Polar Regions are even more marked and all land areas are affected. The capacity of the oceans to buffer for the change in temperature is also being tested, and significant temperature rises will be seen in global surface water temperature. This change in temperature affects the amount of water in the atmosphere and the wind patterns, which can carry water over the surface of the earth. At 1.5 °C of warming, a band of decreased precipitation will extend across the southwest United States, Central America, and northern South America. This will extend through the Mediterranean Basin to Western Asia. In the southern hemisphere, a band of decreased precipitation will affect the southwest coast of South America and the Northeast, and this band extends onto the continent of Africa affecting southern Africa and then onto southwestern Western Australia. These changes will be even more marked at 2 °C. These changes in temperature and precipitation will have profound implications for access to water and nutrition and for the security of billions of people.

12.1

Africa

Assessment Report 5 (AR5) of the IPCC reported on projections for Africa (AR5, 3: Africa) (Niang et al. 2014). Within Africa, there are marked differences in the projections for regions as the atmosphere warms. In general, all areas of Africa

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will be affected by temperature rise. It is highly likely that the mean surface temperature will increase by 2 °C by the end of the twenty-first century. The precipitation patterns in Africa will vary. Southern Africa and northwest Africa will experience a decrease in precipitation. Some areas of Africa however can expect an increase in precipitation, especially in the central and eastern zones, but there is uncertainty about this. Overall, it is expected that water insecurity will increase. The report concluded that there is already evidence of shifting ecosystems and species due to climate change. This will have important implications with regard to the factors associated with disease transmission. Populations are already on the move globally with a shift from rural to urban areas. This trend may increase as migration between countries and between continents. Decreasing crop yields and competition for insecure water resources may lead to further migration and raise the likelihood of conflict between countries.

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Adaptation

Even if greenhouse gas emissions into the atmosphere were to decrease immediately, the effect of gases already in the atmosphere will continue to warm the climate for decades and centuries to come. It is important that communities begin to adapt to the new reality of increased temperature. Adaptation can be defined as actions that reduce the effect of climate change (Natural Resources Canada n.d.). Vulnerability is the extent to which the original population is susceptible to climate effects. The patterns of climate change vary markedly as does the ability of a population to withstand the changes. Some areas of the world will be affected less and may have sufficient resources to be able to adapt to the change and repair damage, a marker of resilience. Others, however, particularly lower-income economies, may be subject to extreme climate changes and may not have the economic, social, and political structures to adapt and respond. IPCC AR6 indicated that up to 3.6 billion people are in a highly vulnerable situation (IPCC 2022: AR6. SPM WGII B2). Climate-related disruption is already being seen even at the temperature rise of just over 1 °C. That will become much more pronounced in the coming decades as the temperature rises toward 2 °C. There is evidence that adaptation measures are underway globally. These vary depending on the economic resources of the region, the imminent nature of the threat and local response to climate change. At present, the approach is mostly reactive rather than proactive, but that may change as the crisis evolves. Adaptation measures can be applied to many systems including land and ocean ecosystems, urban and infrastructure, and energy systems and across sectors. For example, climate change is associated with an increased risk of high rainfall events. Cities at present do not have sanitary systems that will be able to process the volume of rainfall. This will result in contamination of water supply and sewage runoff. Adaptation can address this by building capacity in the system for events that were formerly rare and reduce

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the risk to vulnerable populations of enteric infections. Some adaptation measures will support mitigation. An example of this is restoring marshes and flood plains that can accommodate river overflow. These not only serve as a potential source of carbon sequestration but also will help adapt to changing patterns of rainfall.

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Conclusion

The science underlying climate change was clarified in the nineteenth century. Once the link between rising carbon dioxide levels in the atmosphere and a warming atmosphere became known, it was not seen as a threat. By the late twentieth century, however, the negative consequences of global warming were beginning to be appreciated. More powerful computers permitted the development of projections regarding what might happen as the atmosphere warmed. In addition, populations began to experience more severe rainfall and storm events coincident with the never rising global mean surface temperature. In response to this, the United Nations and other groups began to move countries toward greenhouse gas reduction. At present, it is not clear whether that effort will be sufficient to keep global mean surface temperature below 2 °C by the end of the century. Given that reality, it is important that countries begin to adapt to the new climate realities and prepare for the changes that are coming. This is especially important in Africa where a significant vulnerable population will face increasing challenges of changes in temperature, precipitation, and access to water and nutrition.

References Arrhenius (1896) On the influence of carbonic acid in the air upon the temperature of the ground, London, Edinburgh, and Dublin. Philos Mag J Sci 41:237–275 Carbon brief (n.d.) Explainer: how shared socioeconomic pathways explore future climate change. Climate modelling 19th of April 2018. https://www.carbonbrief.org/explainer-how-sharedsocioeconomic-pathways-explore-future-climate-change Cardinale B, Duffy J, Gonzalez A et al (2012) Biodiversity loss and its impact on humanity. Nature 486:59–67. https://doi.org/10.1038/nature11148 Charlesworth M, Swinton F (2017) Anaesthetic gases and planetary health. Lancet Planet Health 1(6):e216–e217 Clark S (2022) Firmament the hidden science of weather, climate change and the air that surrounds us. Hodder and Stoughton, London. ISBN 9781529362299 EPA (n.d.-a) Overview of greenhouse gases. United States Environmental protection agency. https://www.epa.gov/ghgemissions/overview-greenhouse-gases EPA (n.d.-b) The carbon cycle. https://www.epa.gov/climatechange-science/basics-climate-change Fecht S (2021) How exactly does carbon dioxide cause global warming? https://news.climate. columbia.edu/2021/02/25/carbon-dioxide-cause-global-warming/ Fennell P, Driver J, Bataille C, Davis SJ (2022) Cement and steel - nine steps to net zero. Nature 603(7902):574–577. https://doi.org/10.1038/d41586-022-00758-4

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IPCC (2021) Climate change 2021: the physical science basis. In: Masson-Delmotte V, Zhai P, Pirani A, Connors SL, Péan C, Berger S, Caud N, Chen Y, Goldfarb L, Gomis MI, Huang M, Leitzell K, Lonnoy E, Matthews JBR, Maycock TK, Waterfield T, Yelekçi O, Yu R, Zhou B (eds) Contribution of working group I to the sixth assessment report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, p 2391. https://doi.org/10. 1017/9781009157896 IPCC (2022) Climate change 2022: impacts, adaptation and vulnerability. In: Pörtner H-O, Roberts DC, Tignor M, Poloczanska ES, Mintenbeck K, Alegría A, Craig M, Langsdorf S, Löschke S, Möller V, Okem A, Rama B (eds) Contribution of working group II to the sixth assessment report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, p 3056. https://doi.org/10.1017/9781009325844 IPCC AR6 WGI SPM A 2.1 (n.d.). https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_ AR6_WGI_SPM.pdf Liu PR, Raftery AE (2021) Country-based rate of emissions reductions should increase by 80% beyond nationally determined contributions to meet the 2 °C target. Commun Earth Environ 2: 29. https://doi.org/10.1038/s43247-021-00097 Myhre G, Myhre CEL, Samset BH, Storelvmo T (2013) Aerosols and their relation to global climate and climate sensitivity. Nature Educ Knowl 4(5):7. https://www.nature.com/scitable/ knowledge/library/aerosols-and-their-relation-to-global-climate-102215345/ Natural Resources Canada (n.d.) An introduction to climate change adaptation. https://www.nrcan. gc.ca/changements-climatiques/impacts-adaptation/chapter-1-introduction-climate-changeadaptation/10081 Niang I, Ruppel OC, Abdrabo MA, Essel A, Lennard C, Padgham J, Urquhart P (2014) Africa. In: Barros VR, Field CB, Dokken DJ, Mastrandrea MD, Mach KJ, Bilir TE, Chatterjee M, Ebi KL, Estrada YO, Genova RC, Girma B, Kissel ES, Levy AN, MacCracken S, Mastrandrea PR, White LL (eds) Climate change 2014: impacts, adaptation, and vulnerability. Part B: regional aspects. Contribution of working group II to the fifth assessment report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, pp 1199–1265 O’Neill BC, Kriegler E, Riahi K et al (2014) A new scenario framework for climate change research: the concept of shared socioeconomic pathways. Clim Chang 122:387–400. https:// doi.org/10.1007/s10584-013-0905-2 Our World in Data (n.d.-a) Global greenhouse gas emissions by sector. https://ourworldindata.org/ emissions-by-sector Our World in Data (n.d.-b) Global CO2 emissions from fossil fuels. https://ourworldindata.org/co2emissions Our World in Data (n.d.-c). Annual CO2 emissions. Who emits the most CO2? https:// ourworldindata.org/co2-emissions Putaud JP, Van Dingenen R, Alastuey A, Bauer H et al (2010) A European aerosol phenomenology 3: physical and chemical characteristics of particulate matter from 60 rural, urban, and kerbside sites across Europe. Atmos Environ 44:1308–1320. https://doi.org/10.1016/j.atmosenv.2009. 12.011 RCPs (n.d.). https://climate-scenarios.canada.ca/?page=scen-rcp Tennison I, Roschnik S, Ashby B, Boyd R, Hamilton I, Oreszczyn T, Owen A, Romanello M, Ruyssevelt P, Sherman JD, Smith AZP, Steele K, Watts N, Eckelman MJ (2021) Health care’s response to climate change: a carbon footprint assessment of the NHS in England. Lancet Planet Health 5(2):e84–e92. https://doi.org/10.1016/S2542-5196(20)30271-0. PMID: 33581070; PMCID: PMC7887664 US EPA (2012) The greenhouse effect van Vuuren DP, Edmonds J, Kainuma M et al (2011) The representative concentration pathways: an overview. Clim Chang 109:5. https://doi.org/10.1007/s10584-011-0148-z Weart S (2004) The discovery of global warming. Phys Today 57(6):60. https://doi.org/10.1063/1. 1784277

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Zinezer HA (1944) Meteorological mileposts. Sci Mon 58(4):261–264. https://archive.org/details/ in.ernet.dli.2015.240429/page/n259/mode/2up. Accessed 11 Mar 2022 Zscheischler J, Westra S, van den Hurk B (2018a) Future climate risk: the challenge of compound events. Geophys Res Abstr 20:EGU2018-5439 Zscheischler J, Westra S, Van Den Hurk BJJM, Seneviratne SI, Ward PJ, Pitman A, Aghakouchak A, Bresch DN, Leonard M, Wahl T, Zhang X (2018b) Future climate risk from compound events. Nat Clim Chang 8(6):469–477. https://doi.org/10.1038/s41558-018-0156-3

Current and Projected Climate Changes in African Subregions Kenza Khomsi, Reda El Wakil, Chukwuemeka Onyekachi Nwaigwe, Mohau Mateyisi, and Shingirai Shepard Nangombe

Abstract Africa is a rich continent in natural heritage, but it is facing numerous environmental challenges that are expected to worsen due to the impact of climate change. The Intergovernmental Panel on Climate Change has identified Africa as the region most vulnerable to the impacts of climate change, making it crucial to understand and address the current and future impacts of this phenomenon in the region. This chapter provides a comprehensive analysis of the current and projected impacts of climate change in the five subregions of Africa: Northern Africa, West Africa, Central Africa, East Africa, and Southern Africa. Each of these subregions faces unique climate challenges and is expected to experience rising temperatures, reductions in precipitation, and an increase in the frequency of heat waves (HWs). Northern Africa is expected to see a strong increase in temperatures and a decrease in precipitation, resulting in drier conditions. In East Africa, the projected impacts of climate change include higher annual mean temperatures, more frequent hot extremes, and heat waves. Central Africa is expected to experience an average temperature increase of 0.6–2.1 °C, along with an increase in hot days and extreme heat wave events. West Africa is likely to face increased meteorological droughts, increased wind speed, and changes in monsoon precipitation. Southern Africa is expected to warm faster than the global average, with semiarid and drier areas being particularly vulnerable to the impacts of climate change. In conclusion, this chapter underscores the critical importance of addressing the impacts of climate change in Africa to mitigate its environmental and human impacts. K. Khomsi (✉) Air Quality Department, General Directorate of Meteorology, Casablanca, Morocco R. El Wakil Tropical Medicine Department, Faculty of Medicine, Ain Shams University, Cairo, Egypt C. O. Nwaigwe University of Nigeria, Nsukka, Nigeria M. Mateyisi · S. S. Nangombe Council for Scientific and Industrial Research, Pretoria, South Africa e-mail: [email protected]; [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 A. Saad-Hussein et al. (eds.), Impact of Climate Change on Health in Africa, https://doi.org/10.1007/978-3-031-39466-9_2

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Keywords Climate change · Temperature · Precipitation · Heat waves · North Africa · East Africa · Central Africa · West Africa · South Africa

Abbreviations CAM5 CAR CMIP5 CMIP6 CoLs CORDEX COSMO CRUTEM4 CSIRO DJF DRC ECOWAS GCMs GHG HadCRUT HadGEM3 HWs IPCC ITCZ JAS JFM JJA MAM MENA PSA REMO SON SST TCs WCRP

Community Atmosphere Model version 5 Central Africa Republic Coupled Model Intercomparison Project Phase 5 Coupled Model Intercomparison Project Phase 6 Cut-off lows Coordinated Regional Climate Downscaling Experiment models Consortium for Small-scale Modeling Climatic Research Unit Temperature version 4 Commonwealth Scientific and Industrial Research Organisation December, January and February Democratic Republic of Congo Economic Community of West African States Global Circulation Models Greenhouse Gases Hadley Center for Research Unit Hadley Centre Global Environment Model version 3 Heat Waves Intergovernmental Panel on Climate Change Inter-Tropical Convergence Zone July, August, and September January, February, and March June, July, and August March, April, and May Middle East and North Africa Pacific South American pattern Regional Model September, October and November Sea Surface Temperature Tropical Cyclones World Climate Research Programme

1 Introduction Following Asia, Africa is the second largest continent in terms of both size and population. It encompasses 20% of the Earth’s land area and constitutes 6% of the total surface area of the planet (Sayre 1999). With 1.4 billion people as of 2021, it accounts for about 18% of the world’s human population (United Nations

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Table 1 Countries of the five subregions in Africa Subregions Countries

Northern Africa Algeria, Egypt, Libya, Morocco, Tunisia

West Africa Benin, Burkina Faso, Cape Verde, Côte d’Ivoire, Gambia, Ghana, Guinea-Bissau, Guinea-Conakry, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra, Leone, Togo

Central Africa Cameroon, Central Africa Republic, Chad, Democratic Republic of Congo, Equatorial Guinea, Gabon, Congo Brazzaville, São Tomé and Príncipe

Southern Africa Angola, Botswana, Comoros, Lesotho, Madagascar, Malawi, Mauritius, Mozambique, Namibia, Seychelles, South Africa, Swaziland, Zambia, Zimbabwe

East Africa Burundi, Djibouti, Eritrea, Ethiopia, Kenya, Rwanda, Somalia, South Sudan, Sudan, Tanzania, Uganda

Department of Economic and Social Affairs, Population Division 2022). Africa’s population is the youngest among all the continents; the median age in 2012 was 19.7, whereas the worldwide median age was 30.4 (Abdoulie 2012; Swanson 2015; Harry 2013). Despite possessing a diverse array of natural resources, Africa has the lowest per capita wealth and is the second least wealthy continent in terms of total wealth, ranking behind Oceania. Scholars have attributed this to varied factors including geography, climate, tribalism, colonialism, the Cold War, neocolonialism, lack of democracy, and corruption (Collier and Gunning 1999; Fwatshak 2014). Despite the low concentration of wealth, Africa’s recent economic growth and its significant young population make it a crucial economic market on the global scale in the broader global context with an area of 30,370,000 km2 (11,730,000 square miles) (Britannica 2020). The African continent can be divided into five distinct subregions: Northern Africa, West Africa, Central Africa, East Africa, and Southern Africa. The countries in each subregion are shown in Table 1. In terms of land area, Northern Africa is the most extensive subregion, while Southern Africa is the least extensive. Africa is bounded by four major bodies of water: the Mediterranean Sea to the north, the Red Sea with the Isthmus of Suez to the northeast, the Indian Ocean to the southeast, and the Atlantic Ocean to the west. The continent includes Madagascar and various archipelagos. It contains 54 fully recognized sovereign states. In terms of area, Algeria is the largest country in Africa, while Nigeria has the largest population. In addition, Africa lies across the equator and the prime meridian. According to Visual Geography, this continent is unique in that it extends across both the northern and southern temperate zones. While most of its landmass lies within the tropics, it is noteworthy that the continent also has a considerable number of countries in both the Northern and Southern Hemispheres (Visual Geography 2011).

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Temperature Trend

Precipitation Trend

Fig. 1 Temperature increases due to human-caused climate change are detected across Africa between 1980 and 2015, and many regions have warmed more rapidly than the global average. (Source: Trisos et al. 2022)

Africa is highly biodiverse; it contains the largest number of megafauna species. Despite its abundant natural resources, Africa faces significant environmental challenges such as desertification, deforestation, water scarcity, and pollution. Unfortunately, these problems are deeply entrenched and likely to worsen as the effects of climate change continue to take their toll on the continent. The United Nations (UN) Intergovernmental Panel on Climate Change (IPCC) has identified Africa as the continent most vulnerable to climate change (Schneider et al. 2007). Temperature increases due to human-caused climate change have been detected across Africa between 1980 and 2015, with many regions warming more rapidly than the global average (Fig. 1). Rainfall trends have been detected in only a few regions, and in some cases, different datasets disagree on the direction of the trends (Fig. 1). This uncertainty is due to high interannual and decadal variability, different methodologies used in developing rainfall products, and the lack of highquality of rainfall station data (Trisos et al. 2022). In the future, climate change in Africa is projected to bring increased mean temperatures and temperature extremes across most of the continents and increased mean annual rainfall in the eastern Sahel, eastern East Africa, and central Africa. In contrast, the southwestern Southern Africa and coastal North Africa are expected to experience reduced mean annual rainfall and increased drought. Most African countries are expected to experience elevated temperatures earlier in this century than higher latitude countries, due to their lower internal climate variability. This will result in large increases in the frequency of daily temperature extremes in low-latitude countries earlier in the twenty-first century compared to wealthier nations at higher latitudes (Trisos et al. 2022).

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The objective of this chapter is to discuss the current and projected climate changes in every subregion of Africa.

2 Current and Projected Climate Change in North Africa North Africa is one of the five regions of Africa. It includes Morocco, Algeria, Tunisia, Libya, Mauritania, and Egypt. It is characterized by an arid and a semiarid climate. Rainfall over western North Africa (including Morocco and northern and western Algeria) is of short duration and sometimes intense. The southern region of Mauritania is distinguished by its dry and desertic climate. Climate change and its impacts on the region are already clearly displaying and posing significant challenges in the Northern Africa context to the extent that the region is often considered as a “climate change hot spot” (Diffenbaugh and Giorgi 2012; Zhang et al. 2022).

2.1

Current Climate Change in North Africa

The generalized overview of historical trends in the recent past in the region was drawn by many scholars. Over the past few decades, there has been a noticeable increase in temperature across nearly all regions of North Africa, particularly during summer months and in terms of minimum temperatures (Donat et al. 2014; Waha et al. 2017). The warming trend was accompanied by increases in hot nights, hot days, and heat waves and a decrease in cold waves (Filahi et al. 2017; Khomsi et al. 2016; Nashwan et al. 2019). Trends in temperature were positive in contrast to the negative precipitation evolution in the western parts of Northern Africa. No pronounced precipitation trends have been observed for the eastern regions such as northeastern Algeria (Meddi and Talia 2008), Mediterranean Tunisia (Schilling et al. 2012), central Tunisia (Kingumbi et al. 2005), and the Mediterranean parts of Libya and Egypt (Schilling et al. 2012) during the last decades of the twentieth century. For northeastern Morocco and northwestern Algeria, several studies point to belowaverage annual rainfall rates that have prevailed since about the mid-1970s (Khomsi 2014; Khomsi et al. 2013, 2016; Schilling et al. 2012; Speth et al. 2010). In addition, the southern areas of Morocco’s Atlantic Coastline and the Atlas Mountains experienced multiple instances of reduced precipitation during the winter season in the latter half of the twentieth century, specifically during the periods of 1971–1975 and 1979–1983. However, there were also occasional positive deviations in precipitation patterns during the late 1980s and 1990s (Schilling et al. 2012). Moreover, for the southern parts of the Moroccan Atlantic Coast and for the Atlas Mountains, several periods of below-average precipitation occurred in the second half of the twentieth century, in the winter season. As, for extreme events, it has been shown that, on the global average between 1980 and 2018, the magnitude of heat extremes significantly increased, while that of cold extremes decreased at a faster rate. As a result, the

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prevailing climate in North Africa shifted from a prevalence of cold extremes to one of the hot extremes (Zhang et al. 2022). A study by Russo et al. in 2016 showed that, between 1989 and 2009, the northwestern Sahara experienced 40–50 heat-wave days per year (Russo et al. 2016). Recently, Zhang et al. have shown that the magnitude of heat extremes significantly increased, while that of cold extremes decreased at a faster rate (Zhang et al. 2022). With respect to heavy rainfall events, most parts of North Africa show no significant trends over the last decades (Khomsi et al. 2016; Nashwan et al. 2019), while a general increase in drought frequency could be observed in all countries (Hertig and Tramblay 2017). At the seasonal scale, mean precipitation during the wet season, from October to March, has decreased over the last decades, with the strongest decline over the Mediterranean parts of Morocco and Algeria and parts of Libya, whereas a slight increase in precipitation has been observed over the Mediterranean Egypt (Nashwan et al. 2019; Taibi et al. 2017). For Tunisia, trends are not consistent (Chargui et al. 2018; Fathalli et al. 2019). Since the 1970s, extensive regions of western North Africa have exhibited a winter-drying trend in addition to reduced precipitation levels during the wet season (Hertig and Tramblay 2017; Zittis 2018).

2.2

Projected Climate Change in North Africa

The drying/warming signal over the northern African region is a consistent feature, in both the global and the regional climate change projections under different scenarios (IPCC 2014). Many scholars have used different projection scenarios and modeling tools to simulate the future projections of climate variables considering climate change, and overall, North African areas have recorded a strong temperature increase and a precipitation decrease projected for the near future (Giorgi and Bi 2005; Schilling et al. 2012). Projections under increased greenhouse gas (GHG) forcing show considerable changes in the mean, the variability, and the extremes for temperature and precipitation over the course of the twenty-first century, confirming what was already advanced for the region as one of the major climate change hot spots (Diffenbaugh and Giorgi 2012; Schilling et al. 2020). An application of regional and global climate models by Patricola and Cook in 2010 for Northern Africa shows a strong warming of about 6 °C over northwestern Africa in the twenty-first century compared with the twentieth century (Patricola and Cook 2010). In addition, strong increases in heat waves expressed by a strong increase in warm nights, warm days, and warm spell duration are projected for the whole North African region (Lelieveld et al. 2016). The Regional Model (REMO) 1 showed that temperatures are likely to rise between 2 and 3 °C in North Africa, while

1

REMO is a three-dimensional atmosphere model developed at the Max Planck Institute for Meteorology in Hamburg, Germany, and is currently maintained at the Climate Service Center Germany (GERICS) in Hamburg.

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precipitation is likely to decrease between 10% and 20% by 2050 (Dosio and Panitz 2016; Schilling et al. 2012) under the Special Report on Emissions Scenarios (SRES) A1B scenario2 conditions (Paeth et al. 2009). The temperature rise for Morocco is estimated to be 1.2 °C under the latter scenario and 1 °C under the B1 scenario.3 It is highly probable that North Africa will experience a decline in precipitation ranging from 10% to 20% (Schilling et al. 2012). For western North Africa, Räisänen and his team found that the average precipitation reduction is associated with a reduced number of precipitation days rather than with reduced precipitation intensity (Räisänen et al. 2004). This expected significant warming over the whole area along with a reduction in precipitation mainly over the western part of the region was also confirmed by Bucchignani et al., using the ClimateLimited area Model by the Consortium for Small-Scale Modeling (COSMO-CLM) and assuming the Representative Concentration Pathway 4.5 (RCP4.5) scenario 4 (Bucchignani et al. 2018). The Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble from the World Climate Research Programme (WCRP) 5 projects a highly likely decrease in mean annual precipitation over a generous portion of northern Africa in the mid- and late twenty-first century periods for RCP8.5. 6 The decrease in rainfall is about 10–20% for large parts of northern Africa (IPCC 2013a; Taylor et al. 2012). This decreasing trend was confirmed by dynamical (Ozturk et al. 2018) and statistical downscaling assessments (Dubrovský et al. 2014). Compared with temperature projections, precipitation projections are characterized by a greater degree of uncertainty and are influenced by higher levels of spatial and seasonal variability. In 2018, Bucchignani and his team studied climate projections for a selected set of extreme precipitation indices; more specifically, they explored the percentage changes (%) between the average value over 2071–2100 and 1981–2010 in the Middle East and North Africa (MENA) region. They found that the maximum number of consecutive dry days (CDDs; 35 °C during September–November. There has been an observed warming trend in the mean, minimum, and maximum temperatures between 1981 and 2010. This zone has a single rainy season from March to November and a very dry period from October to February with almost no rain. Precipitation experiences a much higher variability from year to year compared with temperature (Richardson et al. 2022). The altitude of the tropical highlands of Eritrea and Ethiopia results in cooler than average temperatures when compared to the other zones. Annual daily mean temperatures are around 20 °C with little variation throughout the year. The hottest period of the year is the spring season (March–May) when daily maximum temperatures sometimes exceed 30 °C. The coolest period occurs during November– January when daily minimum temperatures drop to around 10 °C. There has been an observed warming trend in the mean, minimum, and maximum temperatures between 1981 and 2010. Within the East African region, this particular zone stands out as being one of the most abundant in terms of rainfall. It has one main rainy season that occurs from June to mid-September in the northwestern areas and during late July to early September in northern parts. The southern areas witness two rainy seasons from February to May and October to January. The long rains that affect the southern areas have observed a decline in seasonal rainfall caused by delayed onset and earlier cessation of the rains rather than a reduction in daily rainfall amounts (Richardson et al. 2022). The Horn of Africa covers northeastern Kenya, Somalia, eastern and northeastern Ethiopia, Djibouti, and southern Eritrea. This zone experiences a hot desert climate in the north and a semiarid climate in the southern part. Temperatures are hot and fairly uniform throughout the year, with a daily mean temperature ranging between 25 and 30 °C and a daily maximum temperature often exceeding 35 °C across most of the region, particularly in the north of the zone where daily maximum temperatures exceed 40 °C during the summer months. There has been an observed warming trend in the mean, minimum, and maximum temperatures over the period between 1981 and 2010 (Richardson et al. 2022). The zone receives rainfall in two key rainy seasons: between March and May and between October and December. The timing

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and amounts of seasonal rainfall are highly variable from year to year, and there has been an observed decline in rainfall during the first season (Wainwright et al. 2021). The highland regions of the East African Rift experiences a largely tropical climate with a wet and dry season, influenced by the variation in topography. They experience cooler temperatures than the other regions with lower temperatures at high altitudes. Daily mean temperatures are below 25 °C throughout the year. Daily maximum temperatures rarely exceed 35 °C due to the higher elevation, although maximum temperatures do consistently reach or exceed 30 °C from October to February during the wet season where precipitation is the highest. There has been an observed warming trend in the mean, minimum, and maximum temperatures between 1981 and 2010, particularly during the wet season. The majority of the region has a single rainy season (September–May), but some parts (Uganda and western Kenya) have more pronounced rainy seasons within this period. Western Kenya receives rainfall during March–May (MAM) and October– December and also during boreal summer June–September. MAM is the wettest season, followed by the summer months of June–August and the short rains of October–December. December–January is the driest season in the year. In Uganda, the wet season is March–November with the drier period from June to August. Precipitation has a much higher variability from year to year compared with temperature particularly during the wet season (Richardson et al. 2022). The lowland region of Tanzania is a hot region with daily mean temperatures ranging between 20 and 25 °C and maximum daily temperatures often exceeding 35 °C during the hottest months (March–May). The coolest part of the year occurs between March and August where daily minimum temperatures fall between 15 and 20 °C. There has been an observed warming trend in the daily mean, minimum, and maximum temperatures between 1981 and 2010. The area experiences a tropical climate with a single rainy season from October to May. The northern part of Tanzania also experiences some of the bimodal long rains/short rains. Precipitation has a much higher variability from year to year compared to temperature, with a mean precipitation at its highest value (above >200 mm) in March and at its lowest value (0–50 mm) during June–September. The precipitation trends observed in Tanzania exhibit a great degree of variability, which can be attributed primarily to the diverse topographical features, the effects of the coastline, and the presence of numerous lakes in the region (Richardson et al. 2022).

3.2

Projected Climate Change in East Africa

Climate model projections for the desert regions of Sudan and Eritrea show high confidence in a projected increase of 2–4 °C in annual mean temperatures in the 2050s relative to the 1981–2010 baseline under a high-emission scenario. Temperatures are projected to increase in all months of the year, with larger increases during the hottest months of the year when average daily maximum temperatures already exceed 40 °C. There is uncertainty in the direction of the projected trend in annual

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precipitation with most climate models projecting an increase and a decrease in some areas. Most of the projected changes occur during the rainy season of June– September. Higher temperatures for longer periods may further increase heat wave frequency and intensity (Richardson et al. 2022). In the tropical regions of Sudan, South Sudan, and Ethiopia, climate model projections show high confidence for a projected increase of 1–4 °C in annual mean temperatures in the 2050s relative to 1981–2010, under a high-emission scenario. Temperatures are projected to increase consistently in all months and seasons and will be associated with an increase in hot extremes. Projected changes in annual precipitation are uncertain, but the majority of climate models project increases in many areas. The largest increase is projected for the summer months (June–September). Smaller increases are projected for the October–December season. A small change is also projected during the March–May season; however, models do not agree on the trend of this change (Richardson et al. 2022). Climate model projections for the tropical highlands of Eritrea and Ethiopia show high confidence in a projected increase in average annual temperatures of 1.5–3.5 °C in the 2050s relative to the 1981–2010 period under a high-emission scenario. Projections indicate that there will be uniform increments across all months and seasons. As this zone is the coolest across East Africa due to the higher elevation, future temperatures will not be as high as in other zones (Richardson et al. 2022). In the Horn of Africa, climate model projections show high confidence in a projected increase in average annual temperatures of 1.5–3.5 °C in the 2050s relative to the 1981–2010 period under a high-emission scenario. There are projections that suggest a rise in temperatures across every month of the year. The average annual precipitation is also projected to increase; most climate models project an increase, and there is higher consensus across the models on this direction of trend compared with the other zones. The projected increase in annual precipitation occurs mainly during the season October–December. Changes in the seasonal rainfall totals during the season March–May are uncertain (Dunning et al. 2018). Variability in the amounts and timings of seasonal rainfall from year to year will continue to be a key feature of the future climate, dominating over any other climate change trend. This interannual variability is also projected to increase relative to the present day, resulting in a higher frequency of wetter and drier years. Heavy rainfall events are projected to increase in frequency and intensity, and there is an indication that dry spells may also increase in frequency and duration (Richardson et al. 2022). There is high confidence in a projected increase in the annual average temperatures of 1–3.5 °C in the 2050s relative to the period of 1981–2010 in the highland regions of the East African Rift under a high-emission scenario. There is uncertainty in the direction and magnitude of the projected changes in annual precipitation, but most climate models project an increase in annual average rainfall. Temperatures are projected to increase in each month of the year, and similar increases are also projected in daily minimum and daily maximum temperatures. The frequency and intensity of hot extremes are also projected to increase. The majority of the climate models project increases in precipitation over the region throughout the year, with the largest increases in October–December (Wainwright et al. 2021). In parts of the

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region that receive both the boreal summer and long and short rains, for example, western Kenya, the projected increase in the short rains suggests potential changes in seasonality, so the season of short rains (October–December) becomes wetter than the boreal summer wet season (June–September) (Wainwright et al. 2021). Interannual variability in rainfall amounts and timings will remain large in the future and is projected to increase. In the lowland region of Tanzania, there is high confidence in a projected increase in the annual average temperatures of 1–3 °C in the 2050s relative to the 1981–2010 baseline under a high-emission scenario. Projected changes in annual precipitation are uncertain, with models projecting both increases and decreases on annual timescales and during the rainy season months in this zone (Richardson et al. 2022). Temperatures are projected to increase in all months of the year, and similar increases are projected in daily minimum and daily maximum temperatures. This could mean that average monthly temperatures in the 2050s may be hotter than the highest temperatures experienced in the current climate. Hot extremes are also projected to increase in frequency and intensity, leading to an increase in heat wave conditions (Pasquini et al. 2020).

4 Current and Projected Climate Change in Central Africa Central Africa comprises the central part of the African continent that contains eight countries: Cameroon, Central Africa Republic (CAR), Chad, Democratic Republic of Congo (DRC), Equatorial Guinea, Gabon, Congo Brazzaville, and São Tomé and Príncipe. The DRC is the largest and the most populous, while São Tomé and Príncipe is the smallest and the least populous. Central Africa is home to an estimated 180 million people (United Nations Department of Economic and Social Affairs, Population Division 2022). The DRC has a population of more than 90 million, while São Tomé and Príncipe has 219,000 people living in it. Central Africa has already experienced widespread losses and damages as the climate has changed at rates “unprecedented in at least 2000 years” due to human activity (IPCC 2021). The region is already facing loss of lives and impacts on human health, reduced economic growth, water shortages, reduced food production, biodiversity loss, and adverse impacts on human settlements and infrastructure as a result of human-induced climate change (IPCC, 2007). The geographical location of Central Africa results in the presence of diverse climate types that can be broadly classified into two categories, namely equatorial and tropical. Some areas of limited extent are subject to mountain climate, such as the Albertine Rift (toward the east of DRC) and the Cameroon volcanic line. Equatorial climate with four seasons stretches up to southern Cameroon and CAR, the center of DRC, in Gabon, in Equatorial Guinea, and in São Tomé and Príncipe (Mpounza and Samba-Kimbata 1990). Precipitations in Central Africa are promptly and seasonally impacted by the behavior of sea surface temperatures (SSTs), especially in the Atlantic Ocean, in

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relation to the dynamics of the ITCZ. Years during which the Southern Atlantic Ocean is warmer than usual show a lack of rainfalls during July–September north to 10°N latitude and during October–December south of Cameroon and then Gabon. Conversely, on the southern fringe of the ITCZ, a warm central Atlantic Ocean goes with some excess of rainfalls, at least close to the ocean. The ITCZ, which is located in the warm central Atlantic Ocean, is associated with a surplus of rainfall, especially in its vicinity, as reported by Tsalefac et al. (2015). The authors also mentioned that the average annual precipitation in this region ranges between 1500 and 1800 mm; however, there are some extreme cases of as much as 10,000 mm of rainfall, such as in Debundscha, situated to the southwest of Mount Cameroon, and in the southern region of Bioko Island in Equatorial Guinea. The climate is warm and humid with temperatures ranging between 22 and 30 °C. Tropical climate, with two seasons, presents several subtypes: Sudanese, Sahelian, and Saharan. Sudanese, Sudano-Sahelian, and Sahelian subtypes are found in North Cameroon, the south of Chad, the center and north of CAR. Moreover, Tsalefac et al. stated that the southern DRC has a more temperate climate due to an average altitude higher than the other areas. Mean annual rainfall ranges from 300 to 1500 mm. Sahelo-Saharan and Saharan subtypes only include north of Chad where the mean annual rainfall is below 300 mm and where maxima temperatures may reach 50 °C (Tsalefac et al. 2015). The equatorial and tropical climates of the Northern Hemisphere are characterized by a dry and sunny main dry season (December to February), while those in the Southern Hemisphere, especially to the Atlantic Coast, have a cloudy dry season cover preserving very high levels of humidity (June–August). The divergent climatic conditions, which are evident on either side of the climatic threshold separating the northern and southern climatic zones, exert a significant influence on the vegetation, and their significance in the context of forthcoming climate variations is frequently underestimated (Gonmadje et al. 2012).

4.1

Current Climate Change in Central Africa

Mean annual temperature across Central Africa has increased by between 0.75 and 1.2 °C since 1960 (Aloysius et al. 2016). The number of hot days and heat waves increased between 1979 and 2016 (Hu et al. 2019), while cold extremes have decreased (Seneviratne et al. 2021). Temperatures in the Republic of Congo have exhibited an ascending trajectory at the regional level. Between 1950 and 1998, there was a marked increase of 0.5–1 °C, with the most significant growth occurring in the 1980s and 1990s (Samba-Kimbata 1991). This trend is accompanied by an increase in extreme temperatures (e.g., the temperature of the hottest day seems to increase by 0.25 °C every new decade), while periods of time with cooler weather have become less frequent in 2006 (Aguilar et al. 2009). Uncertainties associated with the poor ground-based observation networks in the region and associated observational uncertainties result in an assessment of medium confidence in an increase in the number of heat extremes over the region. The severe lack of station data over the

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region leads also to large uncertainties in the estimation of observed rainfall trends and low confidence in changes in extreme rainfall (Creese and Washington 2018). There is some evidence of drying since the mid-twentieth century through decreased mean rainfall and increased precipitation deficits (IPCC 2021). Rainfalls seem to have decreased since the 1950s and especially since the 1970s. A study has noticed a downward trend of total precipitations of 31 mm/decade between 1955 and 2006 (Aguilar et al. 2009) and a decrease in the number of rainy days with precipitations >1 mm and a decrease in the number of days with precipitations >10 mm (Aguilar et al. 2009). Another study found that there is spatial heterogeneity in annual rainfall trends between 1983 and 2010 ranging between -10 and +39 mm per year with a decline in mean seasonal April–June precipitation of -69 mm per year in most regions except in the northwest (Maidment et al. 2015; Zhou et al. 2014). Southern and eastern Central Africa were identified as drought hot spots between 1991 and 2010 (Spinoni et al. 2014).

4.2

Projected Climate Change in Central Africa

At 1.5, 2, and 3 °C of global warming above preindustrial levels, mean annual temperatures in Central Africa are projected to be on average, 0.6, 1.1, and 2.1 °C warmer than the 1994–2005 average, respectively. By the end of the century (2070–2099), warming of 2 °C (RCP4.5) to 4 °C (RCP8.5) is projected over the region (Diedhiou et al. 2018; Fotso-Nguemo et al. 2017; Tamoffo et al. 2019), and the number of days with a maximum temperature exceeding 35 °C is projected to increase by 150 days or more at a global warming level of 4 °C (IPCC 2021). According to the Coupled Model Intercomparison Project Phase 6 (CMIP6) and the Coordinated Regional Climate Downscaling Experiment (CORDEX) models, the annual average number of days with the maximum temperature exceeding 35 °C will increase between 14 and 27 days at a global warming level of 2 °C and 33–59 days at a global warming level of 3 °C above 61–63 days for 1995–2014 (IPCC 2021). The number of heat wave days is projected to increase, and extreme heat wave events may last longer than 180 days at a global warming level of 4 °C (Dosio 2017; Spinoni et al. 2019; Weber 2019). Under low-emission scenarios and global warming levels of 1.5 and 2 °C, there is low confidence in projected mean rainfall change over the region. At global warming levels of 3 and 4.4 °C, an increased mean annual rainfall of 10–25% is projected by regional climate models, and the intensity of extreme precipitation will increase (Coppola et al. 2014; Diallo et al. 2016; Dosio et al. 2019; Pinto et al. 2016; Sylla et al. 2016). At the regional level, a recent comprehensive regional climate change assessment was conducted over the Congo Basin region from 2010 to 2012 where 77 existing and additionally compiled global and regional climate change projections were analyzed for high- and low-GHG emission scenarios, respectively (Haensler et al. 2013a). This study has revealed that for near-surface air temperature, all models, independent from season and emission scenarios, show warming of at

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least 1 °C toward the end of the twenty-first century. The frequency of cold or hot days and nights will decrease or increase, respectively. Since all models are projecting changes in the same direction, the likelihood of these changes to occur is very high. However, the full range of possible changes is large and mainly caused by a few outlier model projections. Therefore, a subrange (the central 66% of projections) defining changes being likely to occur was defined. For near-surface annual mean temperature, the likely changes toward the end of the century are between +3.5 and +6 °C for a high-emission scenario and between +1.5 and +3 °C for a low-emission scenario (Haensler et al. 2013b). In general, projected temperature increase is slightly above average in the northern parts of the region and slightly below average in the central parts. For total precipitation, the results of the different projections are not as robust as for near-surface air temperature. There is considerable discrepancy in the projections for the annual total precipitation in most parts of the Congo Basin region. While certain models indicate an increase, others suggest a decrease over those same regions (Haensler et al. 2013b). However, the same authors are projecting toward the end of the twenty-first century a general tendency for a slight increase in future annual total precipitation for most parts of the Basin. The greatest augmentation in the yearly aggregate of precipitation is anticipated in the drier northern regions, primarily due to the northward expansion of the ITCZ and the relatively low levels of total rainfall recorded in this area. The range likely to occur for changes in total annual precipitation is between -10 and +10% in the more humid zone and between -15 and + 30% in the more arid zone. In contrast, the rainfall characteristics are projected to undergo some substantial changes. It is probable that heavy rainfall events will become more intense in the future, with an anticipated increase of up to 30% in most regions. In addition, the frequency of dry spells during the rainy season is for most parts of the domain projected to substantially increase in the future, indicating a more sporadic rainfall distribution (Haensler et al. 2013b).

5 Current and Projected Climate Change in West Africa The Western African subregion is located geographically between 18°W–15°E and 3–16°N. It is divided into three latitudinal zones: the Sahel in the north (11–15°N), the Sudano-Guinean zone (8–11°N) in the south, and the Guinea Coast (5–8°N) bordering the tropical Atlantic Ocean. As delineated by the United Nations (UN), it is made up of 16 countries, namely Benin, Burkina Faso, Cape Verde, Côte d’Ivoire, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra Leone, and Togo. Jointly, these countries make up an area of 5,114,162 km2 (1,974,589 square miles) and, in 2021, had an estimated population of about 419 million, according to the World Population Prospects (United Nations Department of Economic and Social Affairs, Population Division 2022). The bioclimatic zones of West Africa (which span from the Sahara to the humid southern coast) can be subdivided into five broad belts (east to west), in terms of

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climate and vegetation. These include the Saharan, Sahelian, Sudanian, Guinean, and Guineo-Congolian regions (Nicholson et al. 1998). The climate is characterized by warm northeasterly (Harmattan) winds from the Sahara and moist southwest monsoon winds from the Atlantic Ocean, with highly variable and unpredictable precipitation and rainfall. The Sahara, or Saharan region, spans across the whole northern part of West Africa, formed by the Sahara Desert. The vegetation cover may be absent or sparse, except in depressions, wadis, and oases, where water is found. The variety of arid landscapes vary from sandy sheets and dune fields to gravel plains, low plateaus, and rugged mountains, with an average annual rainfall ranging from 0 to 150 mm. The Sahelian region is a broad semiarid belt, extending from the Atlantic Ocean to Sudan (and to the Red Sea). In terms of climate, it has a unimodal rainfall regime centered in August with an annual rainfall amount between 400 and 600 mm. It has open herbaceous vegetation (steppe and short grass savanna) often mixed with woody plants, also with an ecologically dry season of 8–9 months (Nicholson et al. 1998). The Sudanian region is the domain of the savanna and has an ecological dry season of 5–7 months with an average annual rainfall between 600 and 1200 mm. It contains perennial grasses consisting mainly of the genus Andropogon. The Guinean region is found around south of the Sudanian region, with an average annual rainfall between 1200 and 2200 mm and a dry period of 7–8 months. It could be distinguished from the GuineoCongolian region, which is the wettest in West Africa, with an average annual rainfall between 2200 and 5000 mm (Nicholson 1993). Empirical orthogonal functions performed on West African show standardized anomalies for four variability modes in the Sahelian region, which are independently influenced by large-scale ocean surface and atmospheric conditions in the tropical Atlantic Ocean (Ta et al. 2016). The extreme climatic events in west Africa have been described as irregular and are marked by inconsistent spatiotemporal distribution of the extreme rainfall and drought events (Adaawen 2021). Consequently, in the last several decades, extreme events have led to modifications in periods of rainfall events and drought patterns (Dadzie 2017). These scenarios therefore help to promote the impacts of the climate change on the susceptible countries in the subregion since the frequencies of the extreme events have more impact compared with changes in mean climate events, particularly in terms of causing environmental disasters (Mirza 2003).

5.1

Current Climate Change in West Africa

West African region has become vulnerable to climate change and variability, as extreme weather and climate events have resulted in severe impacts (Economic Community of West African States (ECOWAS) 2022). As a result of global warming in the region, temperatures and frequencies of extreme rainfall events have continued to increase for the past 50 years, in line with an increase in global temperatures (Shepard 2022).

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In 2022, floods hit mainly Côte d’Ivoire and Nigeria (Floods—June, 2022), Chad and Gambia (Floods—July, 2022), and Senegal (Floods—August, 2022), in addition few other African countries, displacing more than 1.5 million people from their settlements (UN Office for the Coordination of Humanitarian Affairs 2022). The (Nyadzi et al., 2020) has reported an increase in sea levels and coastal erosion across the region as major risks that will increase the exposure and vulnerability of local populations and assets. Between May and July 2022, the rainfall season exhibited mixed conditions, such that many countries in West Africa suffer more from the effects of climate-induced disasters in the form of floods and excessive rainfall settlements (UN Office for the Coordination of Humanitarian Affairs 2022), whereas abnormal dryness was reported in central southern Mali and Western Niger, in addition to Gulf of Guinea, Sierra Leone, Liberia, eastern Guinea, and western Côte d’Ivoire. Reports of the UN Office for the Coordination of Humanitarian Affairs (2022) showed that, as of July 2022, some West African zones, namely northern Senegal, southern Mauritania, western Mali, eastern Guinea, western Niger, Gulf of Guinea, and Mono River (from Sierra Leone to Nigeria) continued to have below-average seasonal rainfall, while the western parts of the Sahel (Senegal and the Gambia) and central Burkina Faso and the eastern parts of the region (Chad, Cameroon, and Central African Republic) recorded above normal rainfall conditions. Senegal and the Gambia (western Sahel), central Burkina Faso (the central Sahel), and the eastern Niger, Chad, Cameroon, and CAR (the eastern part of the region) recorded above normal rainfall levels. Severe rains caused flooding, damaged infrastructures and farm lands, and led to fatalities in the affected areas in Senegal, the Gambia, Mali, Chad, and Nigeria. Floods across Nigeria have affected more than 4.4 million people since July 2022, with over 2.4 million people displaced, and more than half of these are in Bayelsa. In addition, about 676,000 ha of farmland have been destroyed. The damage to the current harvest and limited access to income risks elevated emergency food insecurity in the coming months. Moreover, there has been a gradual drying of Lake Chad over the last 40 years, from a land area of over 40,000 km2 to currently just 1300 km2 and the encroachment by the Sahara Desert, which has been attributed largely to the country’s increasing temperatures (Pham-Duc et al. 2020). This crisis has been described by the United Nations as one of the worst in the world, as the lake had shrunken to about 90%, thus forcing more than ten million people across the region to seek emergency assistance (Mohanty et al. 2021).

5.2

Projected Climate Change in West Africa

West Africa has been identified as a climate-change hot spot, and the countries under this subregion are highly susceptible to climate impacts, quite vulnerable to extreme weather conditions, and also possess poor adaptation potential compared with other parts of the world (Fitzpatrick et al. 2020; Gbode et al. 2023).

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In Nigeria, rainfall variability has been predicted, with an increase in precipitation by approximately 5–20% and subsequent flooding in some humid areas of the forest regions and savanna areas in southern Nigeria (Haider 2019). A report by African Development Bank (2022) indicated that climate risks could cost Ghana’s transport sector the sum of US$3.9 billion by 2050 if nothing is done to mitigate the climatic effects. The coastal countries have been more vulnerable to sea level rise, leading to flooding and coastal erosion, whereby about 56% of the coastlines in Benin, Côte d’Ivoire, Senegal, Guinea-Bissau, and Togo will be constantly eroded (United Nations Department of Economic and Social Affairs, Population Division 2022). According to the IPCC, some of the predicted events of climate change in the monsoon season include an increase in meteorological droughts, increases in mean wind speed, monsoon precipitation to increase over the Central Sahel and to decrease over the far western Sahel, a delayed onset of the monsoon season and a delayed retreat, and an increase in monsoon precipitation (IPCC 2022). Rise in sea levels was long predicted to occur along the coastal belt of Nigeria (French et al. 1995). Senegal faces a number of hazard risks: droughts, floods, sea level rise, and coastal erosion, and these create natural hazards that pose the greatest threat to the country’s development goals (United Nations Department of Economic and Social Affairs, Population Division 2022).

6 Current and Projected Climate Change in South Africa Southern Africa encompasses countries such as Angola, Botswana, Eswatini, Lesotho, Malawi, Mozambique, Namibia, South Africa, Tanzania, Zambia, and Zimbabwe and some independent island states such as Comoros, Mauritius, Madagascar, and Seychelles. The climate is predominantly arid and semiarid climate type. According to Davis-Reddy and Vincent (2017), most parts of Southern Africa have a warm and dry subtropical climate experiencing an average annual temperature above 17 °C (Davis-Reddy and Vincent 2017). The summer temperature is the highest over Botswana and Namib deserts reaching as high as 40 °C during the day. Winter is the coldest over the high-lying areas of Lesotho and Zimbabwe. The highest annual rainfall accumulation occurs in the tropics toward the equatorial regions and eastern Madagascar. Assessment Report 5 (AR5) further reflects that the Southern African region is anticipated to warm at a rate higher than global averages with the semiarid and drier southwestern areas likely to experience higher rates of temperature increases (IPCC 2014). The Special Report on Global Warming of 1.5 °C (SR1.5) considers Southern Africa as one of the “climate change hot spots” indicating that the region is one of those where the impacts of climate change are anomalously high as seen from the global climate setting (Hoegh-Guldberg 2018). This factors in the fact that the region is already warm and dry with parts of the subcontinent projected to experience an even warmer and drier future under climate change (IPCC 2014). The projected climate change–induced thermal heating, simultaneous with an increased

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atmospheric moisture, during mid-to-late summer, favors an increased intensity of convective rainfall that is associated with thunderstorms over much of Southern Africa’s interior.

6.1

Current Climate Change in Southern Africa

Studies investigating temperature trends using the Hadley Center for Research Unit (HadCRUT) dataset over Africa, specifically using time series of local gridded datasets of surface temperature products, uncovered the largest warming trends of 0.4 °C per decade observed over subtropical Southern Africa (Davis-Reddy and Vincent 2017). Version 4 of the HadCRUT dataset (HadCRUT4), which has about 84% coverage of the globe, has also been reported to have sampling bias emanating from nonuniformly distributed unobserved regions (Cowtan and Way 2014). The unsampled regions are concentrated over the poles and Africa. For southern Africa, Botswana and Tanzania are some of the countries with major observation gaps, leading to low confidence in finer-resolution trends over the countries. This contributes to uncertainty in the assessment of climate change in Southern Africa. IPCC AR5 contributed methods that are scientifically defensible for evaluating models or studies’ confidence in the historic climate trends and future changes (Collins et al. 2013). Evidence from gridded observation, generated using the Climatic Research Unit Temperature version 4 (CRUTEM4) data (Osborn and Jones 2014), reflects that the warming in the interior of Southern Africa, over the last several decades (1961–2010), happened at about twice the average rate of global warming (Engelbrecht et al. 2015). The oceans surrounding the subcontinent play a key role in moderating temperatures during both summer and winter periods. The cold Benguela Current and upwelling contribute a cooling effect along the southwest coast temperatures, while the warm Agulhas Current results in significantly warmer southeast cost relative to the southwest coast (Department of Science and Technology 2010). A station observation–based study confirmed that the warming is also felt in island states such as Madagascar, which have been warming significantly since 1961 (Tadross 2008). Specifically, minimum temperatures over the island reflect a much established warming signal consistent with global observations. Increases in extreme temperature events such as heat waves and high fire danger days have also been reported in countries like South Africa in connection with the observed general warming signal (Kruger and Nxumalo 2017). The high-lying areas along the southern and eastern escapement within South Africa, which experience relatively low temperatures on account of increasing elevation above sea level, are also found to have experienced a pronounced warming of daytime and night temperature trends (Mateyisi et al. 2021). There is strong evidence that suggests an increase in the number of hot and very hot days and also a decline in the number of cold days consistent with the global warming trend (Field et al. 2012). The decline in the frequency of low temperatures, including the number of frost days, over all

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parts of the interior is likely to continue heading into the recent future (New et al. 2006). Studies of trends in atmospheric circulation, during the period of December– February discovered a trend that is indicative of an increase in the daily frequency of higher pressures over Southern Africa (Hewitson and Crane 2006). These changes in the region may directly be linked to the decline in the frequency of rainy days. A study based on observed records of 104 stations spread over Zambia, Malawi, and Mozambique, for the period of 1960–2005, demonstrated that increases in mean dry spell length and reductions in rainy days frequency are plausible during the rainfall season over the three countries (as defined from planting date to rainfall cessation) (Tadross et al. 2009). According to a review of droughts in Africa by Masih et al. in 2014, countries in Southern Africa mainland have experienced a number of severe droughts within the period of 1900–2013 (Masih et al. 2014). Mozambique is reported as having experienced the highest drought occurred during the period amounting to a total of about 12, while Eswatini (earlier called “Swaziland”) received the least number of occurrences amounting to only 5 drought years. Among the independent Southern African island states, Madagascar experienced about six drought occurrences during the period, while Mauritius and Comoros only reported only one drought year. The attribution of change in drought characteristics to climate change is limited by historic data availability. A study conducted using Hadley Centre Global Environment Model version 3 (HadGEM3) and Community Atmosphere Model version 5 (CAM5) models suggested that anthropogenic influence contributed to the increase in the probability of south Southern Africa’s drought of 2018 (October–December) on average by 1.5 times [0.97, 1.96] and 4.3 times [3.43, 5.46], respectively (Nangombe et al. 2020). Some of the wet extremes, specifically the occurrence of the most intense Category 4 and Category 5 tropical cyclones (TCs), originating from the southwest Indian Ocean, have been detected over the last two decades (Fitchett 2018; Kossin et al. 2020). Cut-off lows (CoLs) bring heavy torrential rains over the western and southern parts of South Africa. Positive trends in CoLs are noted in most southern parts of the region, over the last three decades, with a possible connection to the positive trend in the Pacific South American (PSA) pattern (Favre et al. 2013). Station observations over South Africa confirmed that the period of 1921–2020 saw an elevated probability of “heavy rainfall” (>75 mm) and “very heavy rainfall” events (>115 mm) accompanied by damaging winds, erosion flooding, and hail in a form of thunderstorms (McBride et al. 2022). Interestingly, the study also uncovered that the number of rainy days remains near-constant, during the period, despite the increase in the probability of extreme precipitation frequency. In summary, the station records–driven evidence points to a possibility of increasing frequency of precipitation extremes with a possibility of very large thunderstorms (“super cells”) in parts of the subcontinent, while the count of rainy days remains largely unchanged over the southern interior.

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Projected Climate Change in Southern Africa

Regionally downscaled climate model projections of temperature are mostly plausible, while projection in precipitation manifests a pronounced uncertainty concerning the magnitude and direction of projected change (Christensen et al. 2007; Solomon et al. 2007). The whole southern Africa, like the rest of the continent, is projected to experience warming thresholds greater than global annual mean warming (Davis-Reddy and Vincent 2017). The drier subtropical regions are projected to experience stronger warming relative to the humid regions. To this effect, increases in the temperature of more than 3 °C for parts of the southernmost interior and about 2 °C for the coastal regions of South Africa are projected for the period of 2070–2100 relative to the period of 1975–2005 under the A2 SRES scenario (Davis-Reddy and Vincent 2017). In addition, Engelbrecht et al. (2015) reported future changes of about a 3–5 °C temperature increase relative to the current climate over Africa’s tropical regions that include parts of Southern Africa under a low-mitigation scenario (Engelbrecht et al. 2015). A possibility of an increase in the frequency of heat waves (HWs) with future warmer temperatures was also reported (Mbokodo et al. 2020). For the coastal areas, short-lasting HWs (average of 3–4 days) are expected to increase in frequency under an emission scenario with a high GHG concentration in the future climate. In the foreseeable future, coastal areas are expected to undergo HWs that persist for a relatively brief duration compared with the interior regions (Mbokodo et al. 2020). The study further highlighted that the central interior, specifically the northwestern part of South Africa, is likely to experience the most drastic increase in HW occurrences across the country. In this region, it is anticipated that the frequency of HWs will not only significantly increase but also that the duration of these heatwaves will be relatively longer in the future. A model evaluation study based on two CORDEX models for the end of the twenty-first century (2069–2098) relative to the reference period (1971–2005) suggested that the annual total precipitation over the projection period is likely to decrease, while the maximum number of consecutive dry days (CDDs) is likely to increase (Pinto et al. 2016). The possibility of an increase in the CDDs specifically for Namibia, Botswana, northern Zimbabwe, and south Zambia is corroborated by Giorgi and Gutowski (2015). Over the hyperarid and semiarid areas of Southern Africa, the severity of drought is anticipated to increase in connection with the projected decreases in summer precipitation rates (Shongwe et al. 2009, 2011). On the other hand, the risk of severe storms, including intense heavy rain events and intense thunderstorms in South Africa, is projected to increase with global warming (Scholes and Engelbrecht 2021). These heavy rain events and storms are projected to be more intense and lead to more destructive flood events in areas like Limpopo, Mpumalanga, and Kwazulu-Natal (Malherbe et al. 2013). Extreme precipitation such as floods and droughts may cause severe effects on the human population through disturbances in lifestyle, health, and agriculture among other aspects. Populations in the least developed countries are particularly exposed due to their

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low economic conditions (Haines and Patz 2004). Calamities like droughts, famines, and waterborne disease outbreaks may be caused by extreme events such as heavy rainfall–induced flooding that may be increased in the future. Process-based model studies suggest that frontal rainfall bands will retreat southward, reducing winter rainfall to the southernmost part of the subcontinent (Engelbrecht et al. 2009). The question of how tropical cyclones (TCs) could change in connection with the projected anthropogenic warming is fundamental due to the magnitude of societal impacts of TCs. An assessment of recent publications on cyclones (later than 2010) on climate change impacts on tropical reflects an increase in the intensity and near-storm rainfall rates, respectively, for TCs from the South Indian Ocean (Knutson et al. 2020). The assessment summarizes the projected changes in the characteristics of TCs, under a 2 °C warmer world, taking into account IPCC AR5 methods for evaluating projection confidence (Collins et al. 2013; IPCC 2013b). Both the changes in intensity and near-storm rainfall rates are found to be of medium-to-high confidence levels for the region. The average increase in the intensity is suggested by the considered high-resolution studies to be about 5% (range: 1–10%). The increase in near-storm precipitation rates is projected to be about 14%. The pattern of projected percent change in TC and/or Category 4 and Category 5 TC frequencies comes out as inconclusive for the South Indian Ocean region (Tadross 2008; Yamada et al. 2017). Studies of changes in the sizes of TCs (under IPCC A1B scenario) using a nonhydrostatic atmospheric model at 14-km grid resolution have been conducted for an area that encompasses the South Indian Ocean. The future TC size projections suggest a significant (10%) expansion in the radius of TC at 12 m s-1 azimuthally averaged tangential wind speeds globally over the South Indian basins. These TCs’ intensity, near-storm precipitation rates, and size projections have a strong implication for Southern Africa that receives about 5% of TCs originating southwest of the Indian Ocean having passed through Madagascar and the Mozambique channel (Fitchett and Grab 2014). A regional climate model simulation forced with A2 SRES scenarios, sea surface temperatures (SSTs), and sea-ice specified by the Commonwealth Scientific and Industrial Research Organisation (CSIRO MK3)-coupled global circulation models (GCMs) project a decline in the frequency of closed-low frequencies during certain seasons (Engelbrecht et al. 2013). This leads to reduced extreme rainfall frequency. This is except for Mozambique, where the model evidence suggests an increase in the frequency of intense rainfall. A simultaneous increase in temperature and a decline in rainfall over parts of Southern Africa create ideal conditions for frequent droughts or even their prolonged duration (Engelbrecht et al. 2015; Shongwe et al. 2011).

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7 Conclusion The continent of Africa spans a vast area and boasts a sizable, youthful population. Its borders are defined by the Mediterranean Sea to the north, the Isthmus of Suez and Red Sea to the northeast, the Atlantic Ocean to the west, and the Indian Ocean to the southeast. In addition, it is unique in being the only continent that spans both the northern and southern temperate zones. Climate change is already having a significant impact on the African continent, with temperatures rising and precipitation decreasing in many areas. This is expected to worsen in the future, with temperatures projected to increase by up to 7 °C in the summer and 4 °C in the winter by the end of the twenty-first century under the RCP8.5 scenario. Precipitation is likely to decrease between 10% and 20% in the mid- and late twenty-first century under the same scenario. This decrease is most pronounced in the northwestern parts of northern Africa, with the strongest decline over the Mediterranean parts of Morocco and Algeria and parts of Libya. At the East African region, climate change is already having an impact on the region, with rising temperatures, increased frequency and intensity of dust storms and heat waves, and changes in the seasonal distribution of rainfall. Climate model projections for the region show high confidence in a projected increase in average annual temperatures of 1–4 °C in the 2050s relative to the period of 1981–2010 under a high-emission scenario. There is uncertainty in the direction and magnitude of the projected changes in annual precipitation, but most climate models project an increase in annual average rainfall. The Central African region is currently grappling with far-reaching consequences of climate change, manifesting as the loss of life, health implications, diminished economic progress, scarcity of water, reduced agricultural output, depletion of biodiversity, and detrimental impacts on human habitats and infrastructure. Temperatures in the region have been increasing since the mid-twentieth century, with an increase in the number of hot days and heat waves and a decrease in cold extremes. Rainfall has decreased since the 1950s and especially since the 1970s, with an increase in the intensity of extreme precipitation events. In West Africa, temperatures and the frequency of extreme rainfall events have continued to increase for the past 50 years, resulting in severe impacts such as floods and displacement of people. The World Bank has also reported an increase in sea levels and coastal erosion across the region, which will further increase the exposure and vulnerability of local populations and assets. Coastal countries in West Africa are particularly vulnerable to sea level rise enhanced by climate change and leading to flooding and coastal erosion. Southern Africa is also at risk, with the region projected to warm at a rate higher than global averages, with the semiarid and drier southwestern areas likely to experience higher rates of temperature increases. Increases in extreme temperature events such as heat waves and high fire danger days have also been reported in countries like South Africa in connection with the observed general warming signal. The frequency of low temperatures, including the number of frost days, is likely to continue heading into the recent future. The risk of severe storms, including intense heavy rain events and intense thunderstorms in South Africa, is projected to increase

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with the global warming. These heavy rain events and storms are projected to be more intense and lead to more destructive floods. Finally, it is worthy to mention that the studies across all the regions of Africa are sparse. Significant data gaps exist in relation to the observed parameters that help to have insights about the current climate change and its impacts. This change in climate, with increased heat waves, drought, and water scarcity will have a significant impact on the people of the continent. It is therefore essential that academia (scientists), governments, and international organizations take action to document the climate change in Africa, mitigate its effects, and ensure that the people are protected from its impacts.

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Impacts of Climate Change on Environmental Toxins and Pollutants Causing Liver Health Problems Amal Saad-Hussein and Haidi Karam-Allah Ramadan

Abstract The purpose of this chapter is to illustrate the impacts of climate change on environmental pollutants, chemical or biological pollutants, which are causing liver health problems. Liver diseases reflect broad disparities all over the world. The persistence of exposure to environmental chemical pollutants is proved to be affected by climate change stressors, such as variations in the atmospheric temperature and precipitation, sea level rise, and wind speeds and directions. An increase in temperature, as an example, may enhance the release, degradation, transportation, and mobilization of chemical pollutants. Wind speeds and directions affect mainly transportation, dispersion, and deposition of air pollutants that affect the burden of illness and mortality associated with them, and stagnation of the wind speed increases the concentration of pollutants. It was proved that global climate change has an impact on the biological pollutants through changing the distribution and movement of aquatic pollutants to higher latitudes, in addition to an increase in the growth of air biological microorganisms such as fungi with the increase in mycotoxin production. Therefore, climate changes have proved to have increased toxicity and bioaccumulation of the pollutants in the environment and in living creatures. The prediction of climate change impacts on the chemical and biological pollutants is still a formidable challenge for future science. Keywords Climate change · Liver diseases · Africa · Chemical and biological environmental pollutants · Persistent organic pollutants · Heavy metals · Fine suspended particulate matter · Mycotoxins

A. Saad-Hussein (✉) Department of Environmental & Occupational Medicine, Environment & Climate Change Research Institute, National Research Centre, Cairo, Egypt e-mail: [email protected] H. K.-A. Ramadan Department of Tropical Medicine and Gastroenterology, Faculty of Medicine, Assiut University, Assiut, Egypt e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Switzerland AG 2023 A. Saad-Hussein et al. (eds.), Impact of Climate Change on Health in Africa, https://doi.org/10.1007/978-3-031-39466-9_3

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Abbreviations AFB1 AFM1 ASIR BPA CCl4 HBV HCC HCV HIV MC NAFLD OCPs OPPs PBDEs PCBs PCE POPs SSA TASH TCE VC VOCs

Aflatoxin B1 Aflatoxin M1 Age-standardized incidence rates Bisphenol A Carbon tetrachloride Hepatitis B Virus Hepatocellular carcinoma Hepatitis C Virus Human immunodeficiency virus Microcystins Non-alcoholic fatty liver disease Organochlorine pesticides Organophosphates pesticides Polybrominated diphenyl ethers Polychlorinated biphenyls Perchloroethylene Persistent organic pollutants Sub-Saharan Africa Toxicant-associated steatohepatitis Trichloroethylene Vinyl chloride Volatile organic compounds

1 Introduction The purpose of this chapter is to illustrate the impacts of climate change on environmental chemical toxins and biological pollutants that may cause liver health problems. Liver diseases reflect broad disparities all over the world. In sub-Saharan Africa (SSA), the highest age-standardized cirrhosis-related deaths (32.2) were reported between 1990 and 2017 according to the 2017 Global Burden of Disease study. Chronic hepatitis C virus (HCV) represented the lowest proportions of cirrhosis-related mortality in western SSA (7.8%), while chronic hepatitis B virus (HBV) resulted in the highest cirrhosis-related mortality (48.9%). In 2017, 41.5% of cirrhosis-related mortality in Egypt was caused by HBV, and 34.4% was caused by HCV. Meanwhile, mortality due to alcohol-related cirrhosis was the lowest in North Africa and the Middle East (5.3%) and in Egypt specifically (4.8%) (Sepanlou et al. 2020). Moreover, hepatitis B virus, hepatitis C virus, and alcohol represented 47%, 23%, and 20% of hepatocellular carcinoma (HCC), respectively. However, in 10%, the underlying etiology of HCC is not known yet (Spearman and Sonderup 2015).

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The reported prevalence of nonalcoholic fatty liver disease (NAFLD) in Africa among the general population is likely to be underestimated. However, the long-term impact of increasing obesity and type 2 diabetes mellitus prevalence makes NAFLD a hidden danger in this region (Paruk et al. 2019). Almobarak et al. found NAFLD in 20% of 100 asymptomatic Sudanese patients (Almobarak et al. 2014), and Onyekwere et al. reported a prevalence of 4.5% among 44 Nigerians (Onyekwere et al. 2016). In a meta-analysis study published in 2016, the global prevalence of NAFLD was estimated to be 25.2% of liver diseases, with the highest prevalence in the Middle East (31.8%) and the lowest rates in Africa (13.5%) (Younossi et al. 2016). Hepatocellular carcinoma (HCC) represents the fourth most common cancer in Africa, and it is estimated to be 7.8% with 8.4 age-standardized incidence rates (ASIRs) per 100,000, with Egypt (32.2) and Gambia (23.9) having the highest ASIRs in that region (Bahri et al. 2011). The incidence of HCC in North Africa is lower than in SSA, due to lower levels of viral hepatitis and low consumption of alcohol and exposure to aflatoxins, except in Egypt due to the previous high prevalence of HCV infection (4.6%), which was the primary risk factor in this country (Bahri et al. 2011), compared with 0.2% in Morocco and Algeria and 0.7% in Libya (Parkin et al. 2014). However, due to the Egyptian health authorities’ efforts for the elimination of HCV from Egypt, as a special priority, a decrease in the number of HCC cases is expected in the future (Ezzat et al. 2021). Meanwhile, in SSA, HCC is the second leading cancer for men and the third for women (Wiredu and Armah 2006). Emerging risk factors such as diabetes mellitus, NAFLD, and coinfection have the potential of complicating the problem of HCC in Africa, because these risk factors are more difficult to manage than infectious pathogens (Ofosu et al. 2018). Factors like coinfection (HBV/HCV/human immunodeficiency virus (HIV)) in SSA also result in a more aggressive disease with earlier onset (Kew 2010). Aflatoxin has been shown to be an important risk factor either alone or in synergism with HBV and HCV infections in the initiation of HCC. The introduction of Aflasafe as a natural product for minimizing aflatoxin contamination, to check the toxin-producing Aspergillus flavus, will hopefully lead to a reduction in aflatoxin-induced HCC (Okeke et al. 2020).

2 Effect of Climate Change on the Environmental Chemical Pollutants The persistence and transportation of chemical pollutants in the environment are proved to be affected by climate change stressors, such as deviation in temperature, precipitation, sea level rise, and wind speeds and directions (Balbus et al. 2013). However, uncertainty in future emissions of greenhouse gases influences the uncertainty in projected impacts of climate change on the fate and bioaccumulation of the

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environmental pollutants (Gouin et al. 2013). An increase in temperature may enhance the release, degradation, transportation, and mobilization of chemical pollutants that will increase the toxicity and bioaccumulation of these pollutants in the environment and in the body of the exposed living creatures (Kibria et al. 2021). Therefore, air quality could be affected through changes in the speed of chemical processes in the atmosphere due to climate warming, humidity, or acidic precipitations, where pollutants mix and react with each other (Gouin et al. 2013). Moreover, changes in wind speed will also affect the transport of pollutants from place to place, and stagnation of the wind speed increases the concentration of pollutants. Meteorological conditions proved to affect transportation, dispersion, and deposition of air pollutants; therefore, the concern that climate change affects the burden of illness and mortality associated with pollutants, such as gases and fine particulates, will be increased. Therefore, volatilization of persistent organic pollutants (POPs) could be increased with the increase in the atmospheric temperature due to climate change, thereby increasing the amounts subjected to long-range transportation (Gouin et al. 2013), for example, the reappearance of organochlorine pesticides (OCPs) in the atmosphere of Parangipettai in India, after the drastic decline in atmospheric OCPs due to the strict banning of POPs used for the agricultural purpose (Chakraborty et al. 2019). Tropical climate in south India facilitates the release and reemission of the metabolites of OCPs from the previously used sources before the strict banning. Increases in temperature and changes in moisture content due to climate changes are likely to alter the persistence of these chemicals (Breivik et al. 2007). Therefore, an increase in atmospheric temperature not only causes local contamination problems, but also contributes to pollution in areas far away from the point sources via atmospheric transport (Chakraborty et al. 2019). Therefore, climate change may affect the transport and transformation of toxic chemicals in the natural environment (Gouin et al. 2013). Figure 1 summarize the common mechanisms of the impact of climate change on the chemicals in the environment, that will affect it`s toxicity either by increasing or decreasing the toxicity of these chemicals (Fig. 1).

3 Environmental Toxins and Pollutants Causing Liver Health Problems The liver is considered a principal organ in detoxification of a large amount of xenobiotics or foreign chemicals that entered the body. Hence, long-term environmental exposures to chemicals will lead to chronic intrahepatic exposure to these substances and manifest as altered liver function and liver disease (Christensen et al. 2013). These hepatotoxic chemicals are categorized according to their main sources into either industrial pollutants or environmental toxins. Figure 2 summarizes the most common toxic chemicals affecting the liver. Toxicant-associated steatohepatitis (TASH) occurs in workers highly exposed to chemicals occupationally. TASH includes hepatocyte necrosis rather than apoptosis

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Fig. 1 Mechanisms of the impact of climate change on chemicals and their toxicity

Fig. 2 The most important hepatotoxic chemicals affecting the liver

seen in alcoholic or nonalcoholic steatohepatitis, insulin resistance with altered adipokines, higher proinflammatory cytokine, lowered antioxidants, and mitochondrial dysfunction (Cave et al. 2010; Shi et al. 2012). TASH could occur with normal

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serum aminotransferases and has been described in many forms of hepatotoxic chemicals (Cave et al. 2010).

4 Chemical Environmental Pollutants Hazardous to the Liver 4.1

Chloroalkenes

Chloroalkenes include vinyl chloride (VC), tetrachloroethylene or perchloroethylene (PCE), and trichloroethylene (TCE). These chemicals have been used widely as degreasers and dry-cleaning fluids (Wahlang et al. 2013).

4.1.1

Vinyl Chloride

Vinyl chloride (VC) is used for polyvinyl chloride (PVC) production and for the synthesis of chlorinated solvents. It is present in water pipes, window frames, insulation, waterproof clothes, medical and dental appliances, and cigarette smoking (Barsouk et al. 2020). The associations between VC exposures and several liver pathologies including HCC and cirrhosis (Mastrangelo et al. 2004), peliosis hepatis, and focal hepatocytic hyperplasia (Tamburro et al. 1984) were documented. VC disturbs the liver endothelium, causing portal hypertension and the rare angiosarcoma of the liver. Therefore, it is classified according to the International Agency for Research on Cancer (IARC) to be in group A, that is, definite to be human carcinogenic chemical.

4.1.2

Trichloroethylene

Home indoor air contamination may occur as common office and household products such as typewriter correction fluid, paint removers, adhesives, glues, and spot removers contain trichloroethylene (TCE) (Williams-Johnson 1997). The largest source of environmental contamination that stems from TCE is the evaporation from factories that utilize it for the removal of grease from metal. TCE could cause groundwater contamination (Wahlang et al. 2013). Hepatotoxicity is documented following TCE exposures and more closely resembles autoimmune hepatitis.

Impacts of Climate Change on Environmental Toxins and Pollutants. . .

4.1.3

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Perchloroethylene

Perchloroethylene (PCE) is largely used as a chemical intermediate, dry-cleaning fluid, and degreaser. TASH was noted in a study of 29 dry-cleaning workers exposed to 16-ppm PCE in their workplaces (Brodkin et al. 1995). In addition, a significant high risk of liver cancer cases was documented in female launderers and dry cleaners (Lynge and Thygesen 1990).

4.2

Chloroalkanes

Chlorinated alkanes, including chloroform, carbon tetrachloride (CCl4), dichloroethane, trichloroethane, and tetrachloroethane, have been used as industrial solvents, as chemical intermediates, and, in medicine, as anesthetic agents. Exposure to these compounds has been associated with TASH and acute liver failure. They remain in use in industry as degreasers because of their superior properties as solvents of organic molecules and are particularly common in the dry-cleaning industry (Wahlang et al. 2013).

4.2.1

Carbon Tetrachloride

Carbon tetrachloride (CCl4) was in widespread use as a solvent, vermicide, and refrigerant and in fire extinguishers. CCl4 is a ubiquitous ambient air pollutant and may also contaminate groundwater supplies. It remains the classic experimental model for the induction of hepatic cancer in experimental studies, and occupational hepatotoxicity could be detected among occupational exposed workers (Wahlang et al. 2013).

4.2.2

Chloroethanes

1,1,1-trichloroethane (methyl chloroform) was widely used as an industrial solvent and was present in many household cleaners and adhesives until its use was stopped due to ozone depletion (Midgley and McCulloch 1995). Toxicity causes mild elevation of the liver enzymes, centrilobular necrosis, and mild fatty change (Brautbar and Williams II 2002).

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Volatile Organic Compounds (VOCs)

Volatile organic compounds (VOCs) such as benzene, toluene, styrene, and xylene are colorless, flammable liquids that evaporate quickly into air. Petrochemical workers, painters, and printers are frequently exposed to VOCs. Exposures to VOCs have been associated with TASH with both normal and abnormal liver enzymes (Cotrim et al. 1999; Brautbar and Williams II 2002). The exposure could be higher indoors than outdoors depending on how often the windows are opened and the proximity of the home to industrial and traffic pollution (Agency 2017; Cleary et al. 2017). In addition, VOCs are often ingredients in common household products, such as paints, varnishes, cleaning supplies, degreasing agents, gasoline, and dry-cleaned clothing. Therefore, human exposure occurs either by inhalation or by dermal absorption (Agency 2017). However, VOCs may contaminate surface and groundwater in industrial waste disposal areas. In Nigeria, industrial chemicals like VOCs were reported to be a common pollutant found in water bodies and underground waters, soils and sediments, biological systems, and ambient air at different concentrations with seasonal variations (Egbuna et al. 2021).

4.4

Persistent Organic Pollutants (POPs)

These chemicals persist in the environment, have the ability to be transported over long ranges and across the food chains, and bioaccumulate in human and animal organs. POPs include dioxins and polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), organochlorine pesticides (OCPs), and polycyclic aromatic hydrocarbons (PAHs).

4.4.1

Dioxins and PCBs

Dioxins and polychlorinated biphenyls (PCBs) are structurally similar to polychlorinated aromatic persistent organic pollutants (POPs).

Dioxins They are persistent environmental contaminants and unwanted by-products of industrial processes such as incineration, metal processing, and pesticide production. Dioxins are found in air, sediments, and soil. Most human exposures occur through food such as poultry, milk, fish, and meat since these persistent compounds are fat-soluble and accumulate in animal fat (Wahlang et al. 2013). Dioxin exposure can

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lead to tumor development and hepatotoxicity (Yang and Rhim 1995; Fader and Zacharewski 2017).

Polychlorinated Biphenyls (PCBs) These compounds were used as heat-transfer fluids in electric capacitors, wax extenders, and flame retardants. PCBs are present in the ecosystem, including the atmospheric air, lakes, rivers, fish, human adipose tissue, serum, and breast milk and can contaminate food supplies (Schecter et al. 2010). The concentrations of dioxinlike polychlorinated biphenyls (DL-PCBs) in the blood samples from Africa were in the same range as those from Asia but lower than those from Europe. The reported sources were industrial emissions, obsolete pesticide stockpiles, household heating, electronic waste recycling, and incineration and combustion of domestic waste. Meanwhile, the concentrations of dioxins and dioxin-like compounds in the atmosphere in Africa were comparable to and/or higher than those in the developed countries (Ssebugere et al. 2019). PCBs have long been associated with hepatotoxicity, and they have only recently been associated with NAFLD (Wahlang et al. 2019).

4.4.2

Polybrominated Diphenyl Ethers (PBDEs)

They are widely used as fire retardants, and they easily volatilize into the surrounding environment during their production and usage; therefore, human exposure is widely found (Klinčić et al. 2020). PBDEs are also frequently detected in both diet and human milk (Zhang et al. 2017). Previous studies in animals have indicated that they can cause hepatic injury and the mechanisms may be through the disturbance of glycolipid metabolism, oxidative stress, inflammation, and mitochondrial dysfunction (Zhu et al. 2019; Sun et al. 2020).

4.4.3

Pesticides

Some pesticides including organochlorine pesticides (OCPs) and triazine herbicides may be associated with TASH. Climate change is likely to have a variable impact on the fate of pesticides due to the increase in the atmospheric temperature and may also lead to transportation of pesticides to contaminate groundwater, due to the changes in rainfall seasonality and quantities (Bloomfield et al. 2006). They also mentioned that all these effects could be difficult to be predicted as there is no direct acute impact that could be detected, and it needs a long period to be shown. Experimentally, the toxicity of chlorpyrifos pesticide increases with the increase in the surrounding temperature, as its sublethal concentrations decrease, and it was suggested that heat waves due to climate change may increase the risk of the toxicity of

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Fig. 3 Role of climate change in the hepatic effect of pesticides

pesticides in general (Quiroga et al. 2019). Figure 3, summarizes how climate change may increase the toxic effects of the pesticides on the liver (Fig. 3). Recently in Nigeria, pesticides were reported to be one of the commonest pollutants that contaminate water sources, either surface or underground waters, and also contaminate soils and sediments and ambient air at different concentrations with seasonal variations (Egbuna et al. 2021).

Organochlorine Pesticides (OCPs) OCPs include but are not limited to dichlorodiphenyltrichloroethane (DDT). They are thermodynamically stable POPs that continue to contaminate living organisms and the human food supply. Human exposure can occur via inhalation, dermal contact, or ingestion of the contaminated food. A recent analysis of POPs in South Africa estuaries between 1960 to 2020 has shown that the concentration of OCPs in water were below the World Health Organization (WHO) limits, while those in fish tissues from most estuaries were below the United States Food and Drug Administration (US FDA) limits (Olisah et al. 2021). Several African countries still use OCPs especially for the prevention and control of malaria; however, there is still a gap in the published reports on OCPs in Africa and their potential health hazards (Thompson et al. 2017). Pesticides are metabolized in the liver and may increase the risk of liver cancer, through cell adhesion alterations, genotoxicity, cytotoxicity, tumor promotion,

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immunotoxicity, and/or hormonal actions (VoPham et al. 2017). Therefore, occupational human exposures have been occasionally linked to liver cancer (Wahlang et al. 2013). Even OCPs were strictly banned since long time in many countries including Egypt, residual amounts of OCPs were detected in maternal biological components (Elserougy et al. 2013).

Organophosphate Pesticides (OPPs) Organophosphate pesticides (OPPs) are not considered under the persistent compounds; therefore, it was used as safer pesticides after banning OCPs. However, it was found that the hepatic tumor biomarkers in OPPs-exposed workers were significantly high in relative to the control subjects, and their deoxyribonucleic acid (DNA) damage was increased, with shortening of telomere length and decrease in telomerase enzyme activity compared with their controls (Saad-Hussein et al. 2019); the malondialdehyde (MDA) was elevated in the workers exposed to high concentration of pesticides in ill-ventilated workplaces (Saad-Hussein et al. 2022a). It was proved that the workers with homozygous Glutathione S-transferase theta-1 (GSTT1) can detoxify pesticides, and therefore, the risk of hepatic cancer was found to be reduced among them (Saad-Hussein et al. 2022a).

Triazine Herbicides Triazines may contaminate groundwater. Rat chronic exposure to atrazine led to steatosis, obesity, insulin resistance, and mitochondrial dysfunction (Lim et al. 2009).

4.4.4

Polycyclic Aromatic Hydrocarbons (PAHs)

These are formed of two or more fused benzene rings. These compounds are naturally found in fossil fuels, and they are released into the environment as derivatives of incomplete combustion of organic materials, such as charbroiled food products, biomass, woods, tobacco, internal combustion engines, and other commercial sources (Olisah et al. 2021). In a recent systematic review on various emerging pollutants in Nigeria, PAHs were detected to contaminate the water bodies and underground waters, soils and sediments, biological systems, and the ambient air at different concentrations with seasonal variations (Egbuna et al. 2021). Benzo(a)pyrene (BP) is the most common high-molecular-weight PAH causing human and animal cancer (IARC 2022). Moubarz et al. (2022) found that, in aluminum manufacture factory, although PAH concentrations in workplace environment were within the permissible limits, yet evidence of DNA damage was present as expressed by high benzo(a)pyrene diol epoxide albumin adduct levels

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in exposed workers compared with the nonexposed workers. This DNA damage could predispose to the development of cancers in many organs including the liver (Moubarz et al. 2022). Moreover, experimentally in mice model, these compounds induce hepatotoxicity in the form of increased relative liver weight, hepatocyte swelling and degeneration, and elevated serum alanine aminotransferase (ALT) levels. They could induce glutathione depletion and oxidative DNA damage with elevated 8-hydroxy-20-deoxyguanosine (8-OHdG) levels. Hepatic expression levels of the aryl hydrocarbon receptor (AhR), AhR-related target genes, and AhR nuclear translocator (ARNT) were significantly increased in mice study (Tao et al. 2021).

4.5

Nitroaliphatic Chemicals

2-Nitropropane, a high production volume chemical, has been used in numerous applications, including printing inks and dyes, adhesives, waxes, waterproof coatings, and varnish remover, and as a fuel additive. It is the most toxic of the nitroaliphatic compounds, leading to severe hepatotoxicity in humans including fatty change, centrilobular necrosis, fulminant hepatic failure, and carcinogenesis (Fiala et al. 1989; Borges et al. 2006).

4.6

N-Substituted Amide Solvents

N,N-dimethylformamide (DMF) is a solvent commonly used in the synthetic leather and polyurethane industry. Dimethylacetamide (DMAC) is a related solvent used in the manufacture of synthetic fibers and acrylic resins. Human exposure to DMF was linked in case reports to hepatic injury, including steatohepatitis, fibrosis, cirrhosis, and cancer (Redlich et al. 1990; Nomiyama et al. 2001).

4.7

Bisphenol A (BPA)

Bisphenol A (BPA) and its analogs are organic synthetic compounds used in the synthesis of plastics. Living organisms are exposed to air and dust containing BPA, mostly from anthropogenic sources, mainly as a result of thermal destruction of BPA-containing materials and recyclable materials including e-waste, and from the emissions near BPA-manufacturing areas (Vasiljevic and Harner 2021). Bisphenol A, 2,2-bis(4-hydroxyphenyl) propane, a diffusely used phenolic compound is known to be endocrine-disrupting compound confirmed to act as an artificial estrogen (Rubin and Soto 2009). It has been used to manufacture polycarbonate plastics, resin linings of canned food and beverage containers, and medical equipment and as an additive in other types of plastics. BPA could leach from food

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and beverage containers and sealants under normal condition of use, and leaching increases with the change in the temperatures. Therefore, human exposure to low levels of BPA occurs widely via ingestion (Vandenberg et al. 2007). The low binding affinity was estimated to be over 1000–10,000 fold lower than that of estradiol. Therefore, BPA was considered a weak environmental estrogen (Kuiper et al. 1998). It undergoes metabolic conjugation mainly by glucuronidation in hepatic tissue (Pottenger et al. 2000). BPA exposure by increasing lipid peroxidation, and decreasing glutathione content, mediates elevated levels of intracellular reactive oxygen species, which eventually lead to apoptosis induced by endoplasmic reticulum stress (ERS) in nonparenchymal hepatocytes (Asahi et al. 2010). BPA could also induce or suppress specific P450 isoforms in rat liver microsomes (Pfeiffer and Metzler 2004). Moreover, BPA exposure affects the levels of proteins and phosphoproteins involved in different biological processes associated with hepatotoxicity, fatty liver, and carcinoma (Hassani et al. 2018). Hence, BPA exposure can induce oxidative stress, ERS, apoptosis, mitochondrial dysfunction, and inflammation in the liver of rat (Asahi et al. 2010; Hassani et al. 2018).

4.8

Heavy Metals

Heavy metals are present in the environment from both natural and industrial sources. Lead (Pb), chromium (Cr), arsenic (As), mercury (Hg), nickel (Ni), and cadmium (Cd) pose a serious threat when they go beyond permissible limits and cause hepatotoxicity. Heavy metals can induce apoptosis, caspase activation, and hepatocyte ultrastructural changes. Inflammation involving tumor necrosis factor-alpha (TNF-α), proinflammatory cytokines, mitogen-activated protein kinase (MAPK), and extracellular signal-regulated kinase (ERK) pathways has been seen in the event of heavy metal hepatotoxicity (Renu et al. 2021). The highest level of accumulation in the liver was observed with lead followed by cadmium and chromium (Aloupi et al. 2017). Heavy metals induce hepatic injury by the oxidative stress reactions, the depletion of antioxidants, and the activity of nitric oxide synthase enzyme (Renu et al. 2021). Human exposures to heavy metals occur mainly via ingestion, inhalation, and dermal absorption (Al Osman 2019). Heavy metal exposure was associated with nonalcoholic fatty liver disease (NAFLD), nonalcoholic steatohepatitis (NASH), and hepatic fibrosis (Chung et al. 2020; Park et al. 2021). The liver metabolizes heavy metals and then excretes them into the intestines; about 5% is removed through the feces, and 90–95% can be reabsorbed by the enterohepatic circulation (Koyu et al. 2006). As a result, hepatocytes are highly exposed to these compounds, with subsequent liver dysfunction, cell damage, and organ failure (Berrahal et al. 2011; Park et al. 2021). Heavy metals in Africa represent a major health issue. In Western Africa, in Cameroon, the average heavy metal concentrations in groundwater and soils were

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higher than those of the WHO norms (Defo et al. 2015). In Nigeria, heavy metals in the airborne particulate matter (PM) pose a severe health risk from the industrial emissions from steel production with diminished air quality posing health risks to people living in the vicinity of the facility and the workers (Ogundele et al. 2017). Assessment of Heavy Metals in Soils from Witwatersrand Gold Mining Basin in South Africa revealed that As, Cr, and Ni are higher than permissible levels and carcinogenic risk values were both higher than the acceptable values (Kamunda et al. 2016). In East Africa, the mean concentrations of heavy metals in agricultural soils were close to the toxicity threshold limit of the United States Environmental Protection Agency (USEPA) standards of agricultural soils, indicating a potential toxicological risk to the food chain in Kenya (Mungai et al. 2016). In a recent systematic review in Ethiopia, authors implied that the majority of the studies reported high concentrations of toxic heavy metals in foods and drinking water (Mengistu 2021). Recently, in North Africa, in Egypt, the potential ecological risk of the Nile River sediment showed that Cd registered the highest pollution ranking, and southern sites represented the lowest ecological risk relative to the central and northern regions (Goher et al. 2021).

4.8.1

Lead (Pb)

Human exposure to Pb occurs by drinking contaminated water from industries, by the using Pb utensils for cooking, via inhalation of the emissions of vehicles, or by the ingestion of objects exposed to Pb (Yang et al. 2022). Lead is released from exhaust gas, paints, and industrial wastes (WHO 2019). In addition, it was proved that blood lead levels were high in smokers (Repić et al. 2020). Pb acetate can cause increase in the total cholesterol, low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), and triglycerides (Renu et al. 2021).

4.8.2

Chromium (Cr)

Cr and its variants act as carcinogenic agents in the environmental, occupational, and industrial domains. Tannery workers have the potential for exposure to the hazardous effects of chromium salts; it was proved that Cr is in high concentrations in their working environment, which was associated with elevation in chromosomal aberrations and sister chromatid exchange (SCE) (Saad-Hussein et al. 2013). Cr exposure occurs through skin and lungs, and then, it enters into the circulatory system, which is later excreted by the liver (Xiao et al. 2012).

Impacts of Climate Change on Environmental Toxins and Pollutants. . .

4.8.3

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Arsenic (As)

Human exposure to As is via contaminated water and food orally, especially in those ingested sea food contaminated by industrial wastes (Saad and Hussanien 2001), by inhalation that involves workers occupationally exposed to mining activities and agricultural pesticides (Singh et al. 2011), or by smoking as nonoccupational exposure (Saad and Hussanien 2001). The primary source of exposure is the leakage of inorganic As into groundwater (Barsouk et al. 2020). Arsenic mainly induces toxicity via oxidative stress (Li et al. 2016). The exposure to As may lead to hepatomegaly, noncirrhotic portal fibrosis, portal hypertension, hepatocellular carcinoma (HCC), and hemangiosarcoma (Mazumder 2005; Waalkes et al. 2006).

4.8.4

Mercury (Hg)

Exposure to Hg is mainly from thermometers, coal, cement production, dental fillers, and pesticides (Raj and Maiti 2019). Fulminant hepatic failure following Hg exposure have been reported (Al-Sinani et al. 2011). Hg tends to increase the reactive oxygen species leading to DNA damage and lipid oxidation in hepatocytes (Renu et al. 2021). In addition, Hg binds with sulfhydryl groups of the enzymes, leading to their inactivation causing hepatotoxicity (Rana 2008).

4.8.5

Nickel (Ni)

The hepatic effect of Ni is the induction of lipid peroxidation in the liver by the generation of free radicals, which induces cell injury and necrotic changes with the infiltration of inflammatory cells (Sidhu et al. 2004).

4.8.6

Cadmium (Cd)

Cadmium is released from batteries, pigments, coatings, phosphate fertilizer, and plating substances (Rahman and Singh 2019). Cd accumulates in the liver due to both short-term exposure and long-term exposure, from environmental or occupational sources. Following Cd exposure, there will be an increase in the hepatic lipid peroxidation, mitochondrial and microsomal lipid peroxidation, and depletion of glutathione (Karmakar et al. 2000).

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Particulate Matters

Fine suspended particulate matter (SPM) is a suspension of solid or liquid particle in the air. SPM is typically defined by size, with the smaller particles being more hazardous. Fine particles with a diameter of