Understanding climate change: with Sketchnotes 9783662663714

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Harald Lesch · Cecilia Scorza · Katharina Theis-Bröhl

Understanding climate change

UNDERSTANDING CLIMATE CHANGE

Harald Lesch · Cecilia Scorza · Katharina Theis-Bröhl

UNDERSTANDING CLIMATE CHANGE - with Sketchnotes -

Prof. Dr. Harald Lesch University Observatory Munich (LMU) Munich Dr. Cecilia Scorza Faculty of Physics of the Ludwig-Maximilians-University Munich (LMU) Munich Prof. Dr. Katharina Theis-Bröhl University of Applied Sciences Bremerhaven Bremerhaven

ISBN 978-3-662-66372-1 (eBook) ISBN 978-3-662-66371-4 https://doi.org/10.1007/978-3-662-66372-1 © Springer-Verlag GmbH Germany, part of Springer Nature 2023 This work is subject to copyright. All rights are reserved 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. Editorial Contact: Caroline Strunz, Dr. Lisa Edelhäuser Project Management: Bianca Alton Cover illustration: deblik Berlin, using a sketchnote of Katharina Theis-Bröhl Graphic design, typesetting and layout: Judith Bröhl-August Climate-neutral printing (CO2-neutral) with environmentally friendly printing inks certified according to the Cradle to Cradle standard (mineral oil and cobalt-free, alcohol-free printing) Springer is part of the registered company Springer-Verlag GmbH, DE, part of Springer Nature. The registered company name is: Heidelberger Platz 3, 14187 Berlin, Germany

Foreword The existence of the climate crisis is a fact that science has long predicted and has now been accepted in politics and society. We are already beginning to feel its effects on our own bodies, be it periods of heat and drought, increased frequency of forest fires, storms and heavy rainfall, or the melting of mountain glaciers. That is why it is important to finally act, but also to deal with the causes and consequences, because only an understanding of the processes driving climate change leads to insight and results in action. This book is intended to provide an understanding of the causes and consequences of climate change. It is aimed at anyone who wants to acquire more knowledge on this topic. The content is written in sketchnote style and aims to explain complex relationships in a simple and understandable way. What are sketchnotes, and why a sketchnote climate book? Thoughts are not only made up of words, but also of images. That's why our brains are good at capturing and remembering visual information. This is where sketchnotes come in: They combine sketches and notes. The written information is reduced to the essentials and supplemented with suitable visualizations. The goal is not to create art, but to support the content with drawings and set anchors for it in the mind. The trigger for Katharina Theis-Bröhl to deal more intensively with the topic of climate change was the video “Die Menschheit schafft sich ab” (Mankind is abolishing itself ) by Harald Lesch. She was very moved by this lecture and processed its content in a sketchnote, which she shared on Twitter®. This brought her into contact with Cecilia Scorza and her team at Ludwig Maximilian University in

Munich, who were working on a handbook for schools entitled “Climate change: understand and act”. The result of this exchange and subsequent collaboration is this book, which begins by describing the special nature of our Earth. It shows how unique the position of our Earth is in our galaxy and in our solar system, and it clarifies the conditions that make life on Earth possible in the first place. It explains the greenhouse effect, with­out which our Earth would be an ice ball. The components of Earth's climate system are also explained. The difference between weather and climate is pointed out. Man-made climate change, its causes, and effects are shown, and the question of what we can do as humanity and as individuals to mitigate it is asked. Each book chapter begins with an introductory text embedded in a drawing. After that, a double-page spread deals with one topic each, on the left in sketchnote style and on the right as text. The text is mainly provided by Cecilia Scorza and Harald Lesch. On the sketchnote page, text blocks are accompanied by visual icons called visual anchors. Each heading on the text page has a visual anchor, which can also be found in the table of contents, and each chapter has its own background color. The table of contents is designed somewhat differently than usual. Each doublepage spread has a heading, an anchor symbol, and a page reference on a “post-it” whose folded corner reveals the background color of the chapter. This makes it easy to navigate through the book. We are indebted to many people who encouraged and supported us in the creation of this book. A big thank you goes to Lisa Edelhäuser, our wonderful editor, who guided us sensitively and wisely through the process and always had valuable tips at the ready.

A special thanks goes to Peter Lemke of the Alfred Wegener Institute in Bremerhaven, who took a lot of time for discussions when we were brainstorming ideas for the book. He subjected the book to thorough final editing for content and text, an invaluable help. Several members from the Scientists for Future coordination team and the Bremen regional group also deserve great thanks. The climate scientist Zora Zittier was very supportive, especially at the beginning of the process and corrected the texts in the sketchnote pages. The meteorologist Franz Ossing guided the book during the entire development process and repeatedly corrected errors and gave valuable advice in several rounds. Manuela Troschke, as an economist, had a somewhat different view of the book. We would not like to forget Anja Köhne, who with her many years of experience in environmental and climate policy repeatedly provided us with advice. Last but not least, we would like to thank Maja Göpel, whose wonderful book “Rethinking Our World” served as inspiration for the last chapter, the Future View. Roger Wilkins from the Language Center of the Bremen Universities and Julie Borchers, an American scientist and friend have thoroughly checked the English translation and given us valuable advice for a better English wording. We would like to thank them very much for this. Collegial thanks also go to the many sketchnoters and creators whose work inspires Katharina Theis-Bröhl. Special mention should be made here of the American illustrator and friend Melinda Walker, who helped shape Katharina Theis-Bröhl's style with her sketchnotes and graphic recordings. Also the wonderful books by Rachel Ignotofsky with her great drawings were a source of inspiration. Both artists are recommended to the readers of this book.

Special thanks also go to the sketchnoters on site. Jutta Korth from Hamburg, who uses sketchnotes in education, critically analyzed the book as a sketchnoter. Thanks also go to the members of the LernOS group of Katharina Theis-Bröhl, Annelies Vandersickel and Sandra Reithmayr. They have been available for months to discuss the sketchnotes and have always made the meetings a place of creative inspiration. Finally we would like to thank the designer and study friend of Judith Bröhl-August, Stephanie Ebbert, who also subjected the book to a critical artistic eye.

The Authors Harald Lesch is a professor of astrophysics at Ludwig Maximilian University in Munich, a natural philosopher, science journalist and television presenter. The fight against climate change is his special concern, to which he has already dedicated several books. “I find that explaining climate change with sketchnotes has been particularly successful!” Cecilia Scorza holds a PhD in astrophysics. She coordinates public relations and school contacts at the Faculty of Physics at Ludwig Maximilian University in Munich. As an astronomer, she knows how many events had to come together for an habitable planet like the Earth to form. She therefore wants to contribute to its protection. Together with Harald Lesch, she contributed most of the text in this book. Katharina Theis-Bröhl is a professor of physics at Bremerhaven University of Applied Sciences and is involved with Scientists for Future. She has been using sketchnotes since 2015 and has lovingly implemented the most important information on the sketchnote pages visually. Her daughter and graduate designer Judith Bröhl-August supervised the graphic design of the sketchnotes and completed the layout of the book.

Contents 1. HOW SPECIAL IS THE EARTH? ................................................................................. Page 1

n in Quiet Locatio the Galaxy Page 3

The Formation of the Solar Syem Page 5

The Magnet Earth's Proc ic d: Its tive Page Shid 13

The Formation of the Planets Page 7

How Did War Get on the Planet? Page 15

The Habitable Zone of the Solar Syem Page 9

Only the Earth Retained its War Page 17

How the Mn Made the Earth Friendly to Life Page 11

The War on Earth Page 19

2. UNDERSTANDING THE GREENHOUSE EFFECT .......................................... Page 21

The Sun as a Source of Energy Page 23

The Grnhouse Effect Page 33

How Mu Energy Does the Earth Obtain from the Sun? Page 25

The Anthropogenic Grnhouse Effect Page 35

The Earth in Radiative Equilibrium Page 27

The Temperature of Our Planet Without Atmosphere Page 29

Actual Energy uxes in the Atmosphere Page 37

The Role of th Atmosphere e Page 31

How Do Gr nh Gases Absorbouse Thermal Rad iatio Page 39 n?

Contents 3. THE EARTH'S CLIMATE SYSTEM ...................................................................... Page 41

The Clima Syem of the Earth and its Components Page 45

The Difference Betwn Weather and Clima Page 43

Pedosphere and Lithospher Page 55

The Role of the Oceans in Moderating The Changeable Atmosphere the Clima Page 49 Page 47

The Role of the Biosphere Page 57

ce of The Emergen ns the Seaso Page 59

The Role of Clouds Page 51

The Formation of Clima Zones Page 61

The Role of the e Cryosphere in th ce an Radiation Bal Page 53

The Climatic Zones of the Earth Page 63

4. THE CLIMATE CHANGE .......................................................................................... Page 65

Man-Made Clima Change Page 67

Concentr Carbon D ation of the Atmoioxide in sph Page 69 ere

Fdba Procees Page 79

Decline of the Northern Coniferous Fores Page 89

The Influence of Solar Activity Page 71

War Vapor in the Atmosphere Page 81

Thawing Permafro Page 91

The Role of The Role o Nitrous Oxid f Methane in the e Anthropogenic the Anthropog in Grnhouse Effect Grnhouse Effenic e Page 73 Page 75 ct

Reduced Aedo Page 83

Drained Mrs Page 93

Mting of the Grnland Ice Sht Page 85

Weakening of the Marine Carbon Pump Page 95

uorinad Grnhouse Gases Page 77

Desertification of the Rainfore Page 87

Tipping Points Page 97

Tipping Elements in the Clima Syem of the Earth Page 99

Contents 5. EFFECTS OF CLIMATE CHANGE .................................................................... Page 101

Sea Lev Rise Page 103

Implications for the Coaal Regions Page 105

Effects on the War Supply Page 107

Effects on the Biosphere Page 113

Effects on the Atmosphere Page 109

Effects on Cryosphere, Pedosphere and Lithosphere Page 111

Ocean Acidification Page 115

6. WHAT CAN I DO? ..................................................................................................... Page 117

Nd to Act Page 119

There is On ly Li Time Le le Page 121

Psyological Hurdles to Clima Change Mitigation Page 123

Transforma tive Action Page 127

10 Clima Saver Tips for Everyone Page 128

Positive Framing Page 125

Contents 7. A LOOK AHEAD .......................................................................................................... Page 131

The Ecological Footprint Page 133

GEO Enginring - the Way Out? Page 143

Rapid Emiion Reductions Are Poible Page 151

Earth Oversht Day Page 135

“Extrapolating” the Future Page 137

It Nds Rules Page 145

The Energy Turnaround Page 153

Economic Growth and Clima Change Page 139

What Does Politics Nd to Do? Page 149

Rethink How Can We d? rl Our Wo Page 147

How the Energy Transition Can Succd Page 155

Continue as Before, Only Mor e Efficiently? Page 141

!

We Mu Act Page 157

And What Your Pathis Page 159 ?

Afterword ........................................................................................................................... Page 160 Literature .......................................................................................................................... Page 162

1. HOW SPECIAL IS THE EARTH? Earth is the only planet in the solar syem where complex life has evolved and persied over biions of years. Of the more than 4, exoplanets that have bn discovered outside the solar syem so far, only a very few are considered to be pontiay life supporting. This means that planets on whi life sms poible are rare and have very special properties. Many events mu come together for a planet like Earth to form. This shows how special our home planet is.

© Springer-Verlag GmbH Germany, part of Springer Nature 2023 H. Lesch et al., Understanding climate change, https://doi.org/10.1007/978-3-662-66372-1_1

The Milky Way is a spiral galaxy with about 200 billion stars

Position of the Sun in the habitable zone of the galaxy

r Cente

Our solar system is far away from the galactic center

26,000 light years Sun

Area of low stellar density without supernova explosions

Outside a spiral arm

Quiet Location in the Galaxy Our home galaxy, the Milky Way, is a large spiral galaxy with an extent of 100,000 light years. It consists of clouds of gas and dust and is home to about 200 billion stars, many of which are concentrated in the central region of the galaxy, but also distributed along its four spiral arms. Many of these stars are orbited by planets. The Sun is the most important star for the Earth and is located in a quiet region of the Milky Way, about 30,000 light years from the galactic center and slightly outside a spiral arm. It is therefore far away from star-forming regions and thus out of reach of supernova explosions, which would destroy life on Earth with their gamma radiation. On the other hand, the Sun is located in a region where enough elements heavier than helium can be found, such as carbon, silicon, oxygen or magnesium. Thus, all the important building blocks for the formation of planets and for life are present. The Milky Way is so large that the Sun needs 250 million years to complete one revolution around the galactic center, and that is at a speed of 900,000 kilometers per hour. This shows how big our home galaxy is.

1. How Special is the Earth?

3

A gas and dust disk formed from residual matter of a supernova Sun and planets were formed 4.6 billion years ago from the gas and dust disk

All elements from helium to uranium were created during fusion in the star and during the explosion

The Formation of the Solar System 4.7 billion years ago, an ancient star in the Milky Way, 25 times heavier than our Sun, exploded as a supernova. During its lifetime, light hydrogen nuclei in the inner core of this star had fused to form heavier chemical elements. In the process, from helium to iron and then during the explosion itself, all the remaining elements up to uranium were formed. A disk of gas and dust developed from the remnants of this explosion. A lot of gas, mainly hydrogen, collected in the center of the disk. Due to the pressure of gravity this central cloud contracted and from it our Sun was formed. At first it glowed dimly, but as soon as the internal pressure increased and nuclear fusion began, it gained the luminosity it has today. The blasted shells of the supernova also contained elements such as oxygen (O), carbon (C), silicon (Si) and iron (Fe). Their atoms assembled to form crystals such as graphite and silicates. These carbon and silicon compounds later formed the first dust grains. Together with the mainly hydrogen-containing gas, they orbited the still young Sun in the form of a gas and dust disk from the beginning.

1. How Special is the Earth?

5

1. First, the gas planets Jupiter, Saturn, Uranus and Neptune were formed

2. Later, fine dust formed the rocky planets Mercury, Venus, Earth and Mars

3. Due to impacts of other celestial bodies the planets accumulated material

The process took about 100 million years

The Formation of the Planets The dust grains in the disk around the Sun bonded with each other, became entangled, and thus grew into even larger and fluffier dust bundles that collided with each other. In the process, the kinetic energy of the colliding particles was converted into heat, the material softened, and larger chunks of rock formed. This is how the first planetary nuclei were formed. In less than a million years, the gas planets Jupiter, Saturn, Uranus and Neptune were first formed. Far from the Sun, temperatures were so low that they could very quickly bind large amounts of cold gas around their large rocky cores. Later, the cores of the rocky planets Mercury, Venus, Earth and Mars formed. They collected material from other celestial bodies over about 100 million years and grew to planet size. Our solar system today consists of one star (the Sun), four rocky planets (Mercury, Venus, Earth and Mars), four giant gas planets ( Jupiter, Saturn, Uranus and Neptune), many dwarf planets (like Pluto), the moons of the planets, many asteroids and comets. Both asteroids and comets are remnants of the early history of our solar system and thus its original building blocks.

1. How Special is the Earth?

7

Rocky planets

Gas planets

If the planet is in the habitable zone of the star, where water can exist in liquid form, the chance that life will develop increases

Neptune

U ra n u s

Saturn

Jupiter

Mars

E ar th

Venus

Me

rcury

Sun

The Habitable Zone of the Solar System Around every star there is an area where water can exist in liquid form, the so-called habitable zone. If the water around the star is located too close to the star, the water evaporates; too far away, ice crystals form and it freezes. If a planet is located in the habitable zone of a star, this increases the chance that life, as we know it on Earth, can develop in the water. In the solar system, the habitable zone begins behind Venus and extends to Mars. The Earth is therefore in the middle of this zone. However, it is not enough for a planet to be located within the habitable zone of a star, but it must also have enough mass to be able to retain an atmosphere. For example, if Mercury were located where Earth is, it would not have enough gravitational force to create the atmospheric pressure necessary to allow water to remain on its surface in liquid form. For life to develop on a planet with a mass similar to that of Earth, (a) an energy source (e.g., a star), (b) carbon-based organic chemical compounds, and (c) liquid water in which long-chain carbon molecules can form are required. However, as we shall see, in the case of the Earth, other events occurred as well that were very important for the habitability of the Earth.

1. How Special is the Earth?

9

It is assumed that the moon was formed 4.5 billion years ago by the collision of the Earth with the protoplanet Theia Before the collision, the Earth needed only 4 to 5 hours for one rotation

This caused winds to sweep over the Earth's surface at 500 km/h

The presence of the moon slowed the rotation of the Earth to a comfortable 24 hours per rotation

The Earth's axis, which previously wobbled, also stabilized and is now slightly inclined at 23.5°with respect to the ecliptic. This gave rise to the seasons

How the Moon Made the Earth Friendly to Life Based on the analysis of lunar rock samples and the great similarity between Earth and lunar material, it is considered highly probable that a protoplanet named Theia collided with Earth about 4.5 billion years ago. Theia was twice as heavy as Mars. Since both Earth and Theia were hot and viscous, their matter mixed, and large amounts of it were ejected into space. After the violent collision, a large part of the splintered matter fused within a few days to form a sphere that orbited the Earth - the Moon was born. Before this collision, the Earth took only four to five hours for one rotation around its axis, and its rotation axis swayed back and forth. On an Earth spinning that fast, winds would sweep across the surface at up to 500 kilometers per hour. Only the presence of our satellite slowed the Earth's rotational motion to today's 24 hours for one revolution. The axis of rotation was also stabilized by the moon and is today inclined at an angle of 23.5° to the ecliptic. This inclination causes the seasons, significantly reduces weather fluctuations, and provides a temperate Earth climate. The moon made the Earth a more life-friendly planet.

1. How Special is the Earth?

11

Many planets have a weak permanent magnetic field

However, the Earth has a dynamic magnetic field, which is generated by processes maintained in the Earth's interior

Without the protection of the magnetic field, the Earth's surface would be defenseless against the solar wind with its high-energy particles

Probably the iron core of Theia penetrated completely inside the Earth during the collision

So Theia is partly responsible for the heat inside the Earth and the buildup of the Earth'smagnetic field

The Earth's Magnetic Field: Its Protective Shield Many planets in the solar system have a weak permanent magnetic field. The Earth, on the other hand, has a dynamic, strong magnetic field that is maintained by processes in the Earth's interior. The heat in the Earth's interior causes several thousand degrees of hot and ferruginous rock to rise in the direction of the Earth´s surface This cools down, sinks again and is forced into spiral paths by the Earth's rotation. Since iron is negatively charged, a current is generated which in turn forms a magnetic field. Why does the Earth among all planets, have such a strong and dynamic magnetic field? Probably the impact energy of the protoplanet Theia played an important role. Its iron core sank almost completely into the center of the Earth during the collision. Thus, it is partly responsible for the heat in the Earth's interior and enables the buildup of a magnetic field. Without this shield, the Earth's surface would be defenseless against the solar wind. This wind consists of high-energy charged particles that can destroy molecules and make the development of complex living beings impossible.

1. How Special is the Earth?

13

All rocky planets were blazing hot due to many collisions in the beginning

Therefore, when the planets cooled, they were very dry

Some asteroids hit the rocky planets, bringing them water Water already existed in the protoplanetary disk

Due to the migratory motions of Jupiter and Saturn, many waterbearing asteroids were ejected from their orbits

The water accumulated in the form of ice in asteroids and comets

How Did Water Get on the Planets? Earth, like all inner planets, was a glowing ball of molten rock in the beginning. Again and again its surface was hit by asteroids. The collisions kept their temperature very high, over 5,000 °C. Once cooled, the planets were therefore mostly dry. But where did the water come from? Water was already present in the protoplanetary disk. The precious element accumulated in the form of ice in remote areas beyond the orbit of Mars (closer to the Sun, it would have evaporated), including on porous asteroids and comets. The motions of the gas giants Jupiter and Saturn ejected many water-bearing asteroids from their orbits. Many were attracted by the sun, on their way some hit the surface of the inner rocky planets thus bringing them water, which first collected as water vapour in their atmospheres. There it mixed with carbon dioxide, nitrogen, and traces of methane, ammonia, and carbon monoxide. These elements of the primordial atmosphere came from the gas mixture of the protostellar disk, which adhered to the surface of the planets due to the gravitational force, as well as from outgassing of the rocks, impacted comets, and volcanoes.

1. How Special is the Earth?

15

Due to the proximity to the Sun the water vapor (H₂0) in the Venus’ atmosphere was split and H₂ escaped into space

Water vapor accumulated only in the atmosphere of the Earth

Mars could not hold the water vapor because of its low mass

Only the Earth Retained its Water Because of their mass and distance from the Sun, the evolution of the inner planets followed different paths. As a result of its proximity to the Sun and its low mass, Mercury remained dry. The planets Venus, Earth and Mars could bind more gases around their surfaces. Due to its proximity to the sun, the water vapor (H₂O) in Venus' atmosphere was split by the sun's ultra violet (UV) radiation, and the volatile hydrogen component (H₂) escaped into space. Only the heavy carbon dioxide (CO₂) remained in its atmosphere. Today, Venus' atmosphere is a hot hell at more than 480 °C day and night and with an atmospheric pressure 100 times higher than that of Earth. Mars could retain less water vapor due to its small mass and gravity. Today, water is found in ice form at its polar caps, but it changes from solid to gas at 0 °C because of the low atmospheric pressure (sublimation). Otherwise, Mars is a desert planet that probably once possessed liquid water during a very brief phase of its history. Only on Earth did enough water vapor remain in the atmosphere.

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When the Earth cooled, the water vapour condensed, rained to the Earth's surface, and the oceans formed.

Large amounts of CO2 were dissolved in the oceans, making the atmosphere more life-friendly CO2 CO2

Only then life could go ashoree and move onto land

As a result, the ozone layer formed, which protects the Earth’s surface from UV radiation

Later, the plants took up CO2 and converted it via photosynthesis into oxygen

Oxygen Water

The first oxygen was formed by plants in the sea

Sugar Carbon dioxide

The Water on Earth Over time, more and more water vapor accumulated in the atmosphere of the primordial Earth. This increased the atmospheric pressure, and when the Earth's surface cooled, water condensed and rained to the Earth's surface for the first time. In this way, rivers, seas, and oceans were formed. Large amounts of carbon dioxide (CO₂) were dissolved in seawater, and deposited on the sea floor in the form of limestone by the calcareous shells of dead marine organisms. In this way, rain made the Earth's atmosphere, which was much warmer due to the greenhouse gases, water vapor and carbon dioxide, more life-friendly. It rained for an estimated 40,000 years. 3.8 billion years ago, the first life forms emerged on the seafloor around white smokers (alkaline hydrothermal vents), initially only as single-celled organisms, including cyanobacteria. Later, about 2.7 billion years ago, these were the first living organisms to perform photosynthesis. Oxygen was produced and released in the process. An ozone layer formed in the atmosphere, which protected the Earth's surface from UV radiation - an important prerequisite for biodiversity on Earth. About 500 million years ago, plants came ashore and began to absorb more CO₂ and convert it into oxygen through photosynthesis.

1. How Special is the Earth?

19

2. UNDERSTANDING THE GREENHOUSE EFFECT Our planet is irradiad by the Sun and thus receives energy. How mu energy it receives from the Sun is dermined by the diance of the Earth from the Sun. However, our Earth would be an ice ba with a mperature of -18 °C if it did not have an atmosphere. Its composition plays a key role in the grnhouse effect that makes the Earth habitable.

© Springer-Verlag GmbH Germany, part of Springer Nature 2023 H. Lesch et al., Understanding climate change, https://doi.org/10.1007/978-3-662-66372-1_2

FUSION REACTOR SUN p p

p

n

p

n p

+

e⁺ e⁺

+ energy

p

4₁¹H ⇒ ⁴₂He + 2e ⁺+ 2v + ΔE

Every second, the Sun converts 564 million tons of hydrogen into 560 million tons of helium

p: proton, n: neutron, e+: positron, v: neutrino Due to its surface temperature of 5,778 K, the Sun radiates mainly in the wavelength range of visible light

THE SPECTRUM OF THE SUN

Gamma

X-ray

Ultraviolet

10⁻¹²

10⁻¹⁰

10⁻⁸

Visible Infrared Microwaves 10⁻⁶

10⁻⁵

Radio

10⁻² 10³ Wavelength in meters

The Sun as a Source of Energy Like all stars, our Sun is a self-luminous celestial body. It consists of very hot, ionized gas, the so-called plasma. Due to the high pressure of the gas masses, the temperature in the inner core of the Sun is about 15 million °C. At these high temperatures, fusion of atomic nuclei takes place: Four hydrogen atomic nuclei fuse to form one helium atomic nucleus. However, helium has a lower mass (99 %) than the sum of the masses of the four hydrogen nuclei. This mass difference of about 0.7 % is converted into energy according to Einstein's equation E = ∆m ⋅ c2. Thus, the Sun converts 564 million tons of hydrogen into 560 million tons of helium per second, and 4 million tons are converted into energy and radiated out into space. The radiation of the Sun consists of electromagnetic waves, which are divided according to their wavelength into radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma radiation. Due to its surface temperature of almost 5,800 °C, our sun emits mainly light visible to us. This radiation heats up our Earth.

2. Understanding the Greenhouse Effect

23

Earth

The radiation intensity at the location of the Earth is called

Solar constant S0 S0 = 1,361 W/m² s ur

sun

Sun

fac e

of the

radius r = 1 AU

The radiation power of the Sun is distributed outward on spherical surfaces

The short-wave solar radiation is re-emitted from the ground as infrared radiation

Radius r of the sphere with the distance Earth-Sun r = 1 AU = 149.6 • 10⁹ m Surface A of the sphere A = 4πr²

Radiant power L☉ of the Sun L☉ = A•S0 = 4πr² S0 L☉ = 4π • (149.6•10⁹m)² • 1,361 W/m² = 3.83 • 10²⁶ W = 3.83 • 10²³ kW

How Much Energy Does the Earth Obtain from the Sun? The light from the Sun's sphere is emitted equally in all directions. How much of it arrives at a planet depends on its distance from the Sun. Our Earth is about 150 million kilometers away from the Sun and receives a radiation intensity of 1,361 watts per square meter (W/m²), which hits its surface perpendicularly and without the influence of the Earth's atmosphere. This quantity is called the solar constant S0. It can be used to calculate the total radiant power or luminosity of the Sun, L⊙, by placing a sphere around the Sun that encloses all the Sun's radiation and whose radius, r, is equal to the distance between the Earth and the Sun. This distance is also called the astronomical unit (1 AU). Thus, the luminosity of the Sun, L⊙ is obtained by multiplying the area of the sphere A= 4πr² by the solar constant S0. Energy transport from the Sun to the Earth takes place via electromagnetic radiation. In the visible spectral range, i.e. in the wavelength range from 400 to 750 nanometers (nm), the gases in the atmosphere absorb solar radiation only slightly. Most of this visible short-wave solar radiation therefore reaches the Earth's surface, where it is partially absorbed and warms the Earth's surface. The warm Earth radiates this absorbed energy back into space as invisible longwave infrared radiation (thermal radiation).

2. Understanding the Greenhouse Effect

25

1. RADIATIVE EQUILIBRIUM

Emied: 340 W/m²

Irradiad: 340 W/m²

2. DISTRIBUTION OF THE RADIATION The Earth absorbs radiant power on its projection surface LEarth = S0 · πr²Erde = 1.735 · 10¹⁷ W

In equilibrium, the radiad energy and the energy radiad into space mu be equal

However, the radiation is diribud over the entire surface 4πr²Earth

Therefore, the average radiation innsity on Earth is ISun = S0/4 = 340 W/m²

The Earth in Radiative Equilibrium In the long-term, the energy that the Earth absorbs from the Sun corresponds exactly to the energy that is radiated back from the Earth into space. The Earth is thus in radiative equilibrium with its surroundings. All planets of the solar system are in radiative equilibrium with their environment. However, the intensity of the radiation that reaches them varies depending on their distance from the Sun. As we already know, the radiation intensity of the Sun on the Earth is S0 = 1361 W/m2. Since the Earth rotates around its axis, not the whole globe but only one hemisphere is irradiated by the Sun. Meanwhile the other hemisphere is in darkness (it is night). In addition, the Earth is irradiated more parallel towards the poles. On average, the intensity of solar radiation is distributed over the entire surface of the Earth (O = 4πr2Earth). However, the intensity of the solar constant acts only on the cross-sectional area of the Earth (Q = πr2Earth). This is exactly 1/4. Thus, the average intensity of solar radiation on the Earth is ISun = (1361/4) W/m2 = 340 W/m2.

2. Understanding the Greenhouse Effect

27

I in W/m² 1200

Stefan-Boltzmann law T⁴ Room temperature

1 800

Boiling water

600 400 200 0

Snowball Earth -240 -200 -160 -120

Ice -80

-40

0

40

80

120

T in °C

340 W/m²

Albedo α: Reflectivity of surfaces

Reflection 30 % of the radiation is reflected back into space α = 0,3

100 % 30 %

101 W/m² 239 W/m²

The maximum of the energy transport from the Sun to the Earth is in the range of visible radiation

This relatively short-wave radiation is only slightly absorbed by the atmosphere and warms the Earth's surface

Earth

The Earth radiates the absorbed energy as invisible infrared radiation back towards space

The temperature is calculated according to the Stefan-Boltzmann law Temperature calculation T = √⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺⎺ ⁴ (1-α) ISun /σ = 255 K = -18 °C

The Temperature of our Planet Without Atmosphere In radiative equilibrium, the mean temperature of the Earth's surface can be estimated using the Stefan-Boltzmann law I = σ  ⋅ T⁴. This law describes the intensity of radiation I (in watts per square meter) emitted by a body at a given (absolute) temperature T. Sigma (σ) is the Stefan-Boltzmann constant with σ = 5.67 ⋅ 10-8 W/(m2K⁴). The law can be represented graphically. Given a known temperature, one can calculate the radiation intensity of a body or, conversely, infer its temperature from a known radiation intensity. Boiling water has a temperature of 100 °C and radiates into the environment I = 1100 W/m2. Room temperature means 20 °C, which corresponds to I = 410 W/m2 and at a temperature of 0 °C even ice radiates 310 W/m2 into the surroundings. We first consider an Earth without atmosphere. Of the 340 W/m² irradiated to the Earth, 29.65 % of the solar radiation is directly reflected into space by clouds and the Earth's surfaces (Iref = (1–α) ISun = 101 W/m²). This reflectivity of surfaces is called albedo α. Thus, the Earth's surface absorbs a lower intensity W

W

ISun → Earth = (1–α) ⋅ ISun = 0.7025 ⋅ 340 m2 = 239 m2 . Since this rocky Earth is in radiative equilibrium, ISun → Earth  =  IEarth surface. The Stefan-Boltzmann equation is then solved for the temperature T: T= 4

(1–α) ⋅ ISun σ

= 4

239

W m2

5.67 ⋅ 10–⁸

W m2K4

= 255 K = –18 °C

On our planet without an atmosphere, the average temperature would be -18 °C

2. Understanding the Greenhouse Effect

29

The greenhouse effect is what makes life on Earth possible in the first place The natural greenhouse effect ensures that the global mean temperature is 15 °C and not -18 °C 15 °C -18 °C

Trace gases = Greenhouse gases The trace gases have the ability to absorb energy from thermal radiation

The atmosphere consists of 78.1 % nitrogen, 20.9 % oxygen, 0.93 % argon, and trace gases such as water vapor, carbon dioxide, methane, and nitrous oxide

The incident radiation causes the molecules to vibrate, which heats up the gas

The Role of the Atmosphere Without an atmosphere, the Earth would be a ball of ice with an average temperature of -18 °C. Life could never have developed on our planet in the known form. Fortunately, the Earth has an atmosphere. This consists of 78.1 % nitrogen, 20.9 % oxygen and 0.93 % argon. However, only the so-called trace or greenhouse gases such as water vapor (H₂O), carbon dioxide (CO₂), methane (CH4), nitrous oxide (N₂O) and ozone (O3) have an influence on the climate. Their combined share of the atmospheric mass is less than 1 %, but they cause the average temperature on Earth to become much higher. How does this warming occur? 30 % of the solar radiation is reflected back into space by the clouds and the Earth's surface. Therefore, only 70 % of the radiation penetrates the atmosphere and warms the Earth's surface. In radiative equilibrium, the Earth's surface emits the same amount of radiation in the form of thermal radiation. Some of this thermal radiation escapes directly into space. However, most of it is absorbed by the greenhouse gases in the atmosphere. The thermal radiation incident from the ground causes the molecules of the greenhouse gases to vibrate, converting the radiant energy into vibrational energy. After some time, the molecules release this vibrational energy in the form of thermal radiation in all directions, including toward the Earth's surface. This leads to an increase in the temperature of the atmosphere, which is known as the “greenhouse effect”.

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31

With the help of the global mean surface temperature T = 288 K the amount of the thermal radiation absorbed by the atmosphere can be calculated

RADIATION BALANCE Portion absorbed by the Earth

The portion of the thermal radiation of about 39 % that is radiated back to the Earth's surface increases the Earth's temperature

ISun→Earth = (1-α) ISun = β σT⁴ β = 0.6132 1-β = 0.3868

The absorption is described by (1-β)

The part (1-α) of the solar radiation ISun is absorbed from the Earth The part (1-β) of the heat radiation of the surface of the Earth is again radiated back

Iref

ISun

The part β of the heat radiation of the Earth’s surface escapes into space IEarth→space = β σT⁴

ISun→Earth = (1-α) ISun

Iatm→Earth = (1-β) σT⁴

Portion emitted by the Earth

EARTH

The Greenhouse Effect On average, the Earth with atmosphere is in radiative equilibrium and its global mean surface temperature of T = 288 K = 15 °C can be used to calculate the fraction of the surface thermal radiation that is absorbed by the atmosphere and re-radiated to the Earth's surface. Here we assume that the Earth's surface absorbs solar radiation ISun → Earth = (1–α) ISun = 239 W/m2 and, in addition, the downwelling thermal radiation from the atmosphere Iatm → Earth. The atmospheric absorption of the surface radiation reduces the fraction IEarth → Space radiated from the Earth to space by a factor of β. The energy balance of the Earth can now be written as: ISun → Earth = (1–α) ISun = β ⋅ σT⁴ = IEarth → space If we insert the observed surface temperature of the Earth for T, we get β = 0.6132 and 1-β  =  0.3868. This means that almost 39 % of the thermal radiation from the Earth's surface is absorbed by the Earth's atmosphere and radiated back to the Earth's surface as thermal radiation. Calculating this fraction, we get Iatm → Earth = (1–β) ⋅ σT⁴ = 151

W m2

and for the total absorption of the Earth's surface and consequently also the radiation from the Earth's surface IEarth’s Surface = ISun → Earth + Iatm → Earth = (239+151)

W m2

= 390

W m2

.

The Earth's atmosphere causes the Earth to warm up by 33 °C. This process is the greenhouse effect, which is an important determinant of the climate and without which probably no life on Earth would be possible.

2. Understanding the Greenhouse Effect

33

ASSUMPTION What happens when the absorptive capacity of the atmosphere is increased by mankind?

Increased absorption by the atmosphere

42 % (instead of 39 %) of the heat radiation is reflected back to the Earth's surface IEarth’s surf. = 412 W/m²

This means a 4 °C increase of the temperature on Earth T = 292 K = 19 °C

sphere absorbs, the n the atmo warme o i t a i d a r it g r t a ets he e on E r o m art e Th h

The Anthropogenic Greenhouse Effect And now humans come into play: What happens if human beings increase the ability of the atmosphere to absorb thermal radiation by emitting more greenhouse gases? Let's assume that the CO₂ concentration in the atmosphere has increased due to the emission of exhaust gases, and that this now radiates 42 % (instead of the 39 % assumed above) of the thermal radiation back to the Earth's surface. This results in β = 0.58, and for the temperature of the Earth's surface T=

239

4

W m2

W 0.58 ⋅ 5.67 ⋅ 10–⁸ m2 K4

= 292 K = 19 °C

a temperature increase of 4 °C. The proportion of thermal radiation that is reflected back to the Earth's surface thus increases to Iatm → Earth = 0.42 ⋅ σT⁴ = 173

W m2

.

The total radiation on the Earth's surface includes the increased thermal radiation IEarth’s surf. = ISun → Earth + Iatm → Earth = (239 + 173)

W m2

= 412

W m2

.

The absorption capacity of the atmosphere is therefore the adjusting screw in which the whole problem of global warming is. And mankind is currently turning this screw rapidly by increasing the concentration of carbon dioxide through the combustion of coal, oil and gas.

2. Understanding the Greenhouse Effect

35

The Earth’s surface radiates IEarth’s surf. = 390 W/m²

Resulting from long-term global measurements and a complex atmospheric model

This leads to an average temperature of T = 288 K = 15 °C Outgoing Longwave Radiation

Reflected Solar Radiation 101 W/m² 101

239 W/m²

Incoming Solar Radiation

Emitted by Atmosphere

340 W/m²

Greenhouse gases

78 79 Reflected by Clouds

23 Reflected by Surface

160 Absorbed by Surface

Convection 20

30

Absorbed by Atmosphere Evaporation

82

Net absorbed 1 W/m²

Downwelling Radiation

378 22

Latent Heat

Thermals

Atomspheric 22 Window

187

390 Surface Radiation

10

343 333 Absorbed by Surface

Actual Energy Fluxes in the Atmosphere The sketchnote on the left shows the actual energy fluxes in the atmosphere, calculated from long-term global measurements and a relatively complex atmospheric model (Trenberth et al. 2009; Trenberth 2020). Overall, there must be an equilibrium, which means that the energy that is absorbed must also be released. Let us first look at the yellow energy flows: Irradiation from the Sun is 340 W/m² on average. Of these 340 W/m², 78 W/m² are directly reflected by clouds and the atmosphere, and 23 W/m² are reflected by the Earth's surface. Thus, the proportion of reflected solar radiation is 101 W/m² in total. In addition, the water vapor of the atmosphere absorbs another 79 W/m². Of the solar radiation of 340 W/m² incident on the Earth's surface, 160 W/m² is absorbed by the Earth's surface. To this must be added 333 W/m² from the remitted radiation of greenhouse gases, which adds up to a total of 493 W/m². Of this amount of energy, 20 W/m² is converted into the generation of thermal convection and 82 W/m² is used for the evaporation of water. This so-called latent heat is released back into the atmosphere where clouds and precipitation form. In addition, 1 W/m² is assumed to be the net absorption of the Earth's surface in this model. This leaves 390 W/m² that is emitted into the atmosphere. 22 W/m² go directly into space. This leaves 85 %, i.e. 333 W/m², which is absorbed by the greenhouse gases and radiated back to the Earth's surface.

2. Understanding the Greenhouse Effect

37

Energy absorption of atoms

Energy

1.

Energy absorption via the excitation of ectrons by visible light

hf

2. Energy absorption of molecules Energy absorption via excitation of vibrational as by infrared radiation and rotational as by microwaves

CO₂

No dipole

Dipole IR active

Dipole IR active

Dipole IR active

H₂O Dipole IR active

Dipole IR active

Dipole IR active

Absorption of infrared radiation only if the dipolar moment anges during osciation

How Do Greenhouse Gases Absorb Thermal Radiation? When atoms and molecules absorb energy, their state changes. In the case of atoms, this energy absorption occurs through an excitation of the electrons in the atomic shell; in the case of molecules, this occurs through a change in the vibrational or rotational state. Radiation in the microwave range excites molecules to rotate. The infrared radiation with a slightly shorter wavelength excites vibrational transitions of molecules. However, absorption of infrared radiation can only occur if the electric dipole moment changes during the time of vibration. Molecular vibrations with this property are called IR-active. All symmetrical molecular vibrations in which the center of charge does not shift are therefore IR inactive. Dipole molecules, on the other hand, have a constant dipole moment because the electrons are not symmetrically distributed. An example of this is the water molecule (sketchnote bottom left). In contrast, the symmetric CO₂ molecule has no permanent dipole moment because the atoms are arranged linearly and the centers of charge for positive and negative charges coincide. However, the bending vibrations of the carbon dioxide molecule break this symmetry. The resulting dipole moments cause CO₂ to absorb infrared radiation and act efficiently as a greenhouse gas.

2. Understanding the Greenhouse Effect

39

3. THE EARTH'S CLIMATE SYSTEM The Earth's clima is dermined by the solar radiation at the our edge of the atmosphere, the further diribution of energy down to the ground, and the inraction betwn the various major components of the Earth's clima syem: The hydrosphere (ocean, lakes, rivers), the atmosphere (air), the cryosphere (ice and snow), the pedosphere and the lithosphere (soils and solid ro), and the biosphere (living things on land and in the ocean). These components react to exrnal influences at different ras and influence ea other.

© Springer-Verlag GmbH Germany, part of Springer Nature 2023 H. Lesch et al., Understanding climate change, https://doi.org/10.1007/978-3-662-66372-1_3

WEATHER

Hours to days

The current state of the Earth's atmosphere at a given time at a specific place

High pressure area Low pressure area Tropical storms

WEATHER CONDITIONS Weather pattern existing over several days Cold winter

Warm summer

Weeks to months

CLIMATE

At least 30 years

Averaged longterm weather conditions at one location Little ice age Warm period

The Difference Between Weather and Climate To understand how we humans affect the Earth's climate, it is necessary to gain a basic overview of the Earth's climate system. First, we need to distinguish between the terms climate and weather. Weather is the current meteorological state of the Earth's atmosphere at a particular time and place. We perceive the weather directly every day. Weather events take place in relatively short periods of time, ranging from hours to days. Among other things, the weather is determined by the intensity of solar radiation, the geographical distribution of high- and low-pressure areas, convective air currents, humidity, cloud cover and precipitation. Weather conditions is the term used to describe the weather situations that last for several weeks. Stable high- and low-pressure weather conditions can be the cause. The term climate, on the other hand, refers to the weather pattern at a location or in a region averaged over several years, usually with observations over a longer period of at least 30 years. Short-term spikes or anomalies, such as the El Niño phenomenon, are of particular interest to climate researchers. To study climate over the course of Earth's evolution, paleoclimatology even considers periods ranging from hundreds of thousands to millions of years.

3. The Earth's Climate System

43

The components have different reaction rates to changes

Biosphere Living beings

...and thus decisively determine the dynamics of the climate system

Atmosphere Air

osh t i L e pher Rock Hydrosphe re Oceans, la kes, rivers

Pedosphere Ground

Cryosphere Ice and snow

The Climate System of the Earth and its Components Viewed from space, two very different surface features of the planet become visible: the blue oceans and the darker continents. Above both, the atmosphere expands with differently structured cloud systems. The North Pole and South Pole are covered by large areas of ice. These areas form the five main components of the Earth's climate system: · The hydrosphere - ocean, lakes, rivers · The atmosphere - air · The cryosphere - ice and snow · The pedosphere and the lithosphere - soils and solid rocks · The biosphere - living beings on land and in the sea The Earth's overall climate is determined by the solar radiation entering the top of the atmosphere and by the interactions between these five main components of the climate system. All components together form a highly complex system, as they react to external influences at different speeds due to their respective inherent dynamics and they also influence each other.

3. The Earth's Climate System

45

The oceans have an important role in the climate system

They absorb a large part of the solar radiation

- Heat accumulator - Heat transport - Gas storage - Reservoir for the global water cycle

They cover 2/3 of the Earth’s surface (area)

Water stores not only heat, but also CO2, which dissolves in the water when the partial pressure in the air is higher than in the water

CO₂

In addition, ocean currents are very effective at transporting heat from the tropics to high latitudes Water is a very effective heat accumulator and can absorb much more heat energy than air

The Role of the Oceans in Moderating the Climate The oceans are one of the most important elements in the Earth's climate system. They cover about 70 % of the Earth's surface and accordingly absorb a considerable part of the incident solar radiation. They not only store large amounts of thermal energy, but also absorb CO₂ from the atmosphere if the partial pressure there is greater than in the water, which is the case in many areas at high latitudes. The oceans moderate the climate and buffer weather fluctuations and the anthropogenic greenhouse effect. The oceans are the main source of the water cycle: 94 % of the approximately 1.4 billion cubic kilometers of water that exist on Earth is in the oceans. The atmosphere contains only about 0.001 %; its circulation transports 40,000 cubic kilometers of it to the continents, where it can fall as rain. The same amount of water flows back into the oceans. The oceans store around 93 % of the additional greenhouse energy caused by humans and transport it by means of powerful currents. These figures clearly show how important the oceans are for the Earth's climate.

3. The Earth's Climate System

47

It absorbs the long-wave thermal radiation from the Earth's surface and thus ensures comfortable temperatures on the Earth's surface Unfortunately, it is also used as a dumping ground for gaseous waste materials

most e h t s i phere omponent s o m t The a changing c stem y y l s d i p te a r clima of the

In particular the

TROPOSPHERE,

the lowest layer of the atmosphere which is about 10 km thick, ... ... is a place of very changeable weather patterns

Quick compensation of temperature differences in this layer

Violent weather reactions due to colliding air masses

The Changeable Atmosphere The atmosphere is the most variable component of the Earth's climate system; transformation and mixing processes are constantly taking place there. The gases in the atmosphere interact with the Earth's crust, oceans, lakes and rivers, and all living things. In particular, the lowest layer of the atmosphere, the troposphere, is a place of highly variable weather. Here, temperature differences are quickly equalized, and the collision of air masses can lead to violent weather reactions such as storms, thunderstorms, and heavy precipitation. Within hours to days, the atmosphere adjusts to the conditions of the Earth's surface such as the temperature of the ocean or the continents. Unlike water, which is hardly compressible even at high pressure, air is very compressible. 90% of the air is located in the lower layer of the atmosphere. Towards the top, the air pressure decreases and the proportion of oxygen molecules per unit volume decreases, so that the air becomes thinner. Surprisingly, the mixing ratio of the individual gases within the atmosphere remains about the same. With their ability to absorb long-wave thermal radiation from the Earth's surface, the greenhouse gases in the atmosphere ensure that temperatures on the Earth's surface are pleasant.

3. The Earth's Climate System

49

High cirrus clouds ... are almost completely permeable to solar radiation

Dense stratus clouds During the day the clouds reflect the radiation of the Sun and have a cooling effect

Reemission IR

At night, the heat radiation from the ground is reflected back and prevents severe cooling

The Role of Clouds Clouds play a very important role in the climate. They are formed in the atmosphere by the cooling of water vapor, which condenses into cloud droplets. During this cooling process, they give off latent heat and warm up the clouds from the inside. This creates an upward movement (convection) that keeps the clouds in suspension. In addition, clouds can strongly influence the transmission of solar radiation and the thermal radiation of the ground locally. Satellite observations show that clouds partly reflect the incident solar radiation into space, thus cooling the Earth and the atmosphere. On the other hand, they contribute - just like CO₂ - to the natural greenhouse effect by retaining part of the infrared radiation in the system. Whether the cooling effect predominates depends very much on the cloud type: in low stratus clouds, the cooling component far outweighs the warming effect. At night, however, a low cloud cover in winter prevents thermal radiation from escaping into space. So, compared to a starry, cloudless winter night, it remains much warmer. High cirrus clouds, on the other hand, are almost completely transparent to solar radiation and contribute to the warming of the Earth's surface through their greenhouse effect.

3. The Earth's Climate System

51

Areas of ice and snow play a major role in the Earth's radiation balance The proportion of ice and snow on Earth has an immense influence on the temperature behavior The reflectivity (albedo) of ice and snow is much higher than that of water or the ground

Reflectivity Snow / Ice 80 - 90  %

cold

Albedo α Snow fresh: 0.8 - 0.9 Snow old: 0.45 - 0.8 Water: 0.05 - 0.2 Field (unworked): 0.26 Grass: 0.18 - 0.23 Forest: 0.05 - 0.18 Seawater 10  %

warm

The Role of the Cryosphere in the Radiation Balance Ice and snow surfaces also play an important role in the Earth's radiation balance, as both have a much higher reflectivity (albedo) than soil and water. Oceans and the Earth's soil have an albedo of 10 - 20 % and can absorb up to 90 % of incident solar radiation and convert it into heat. Ice and snow, on the other hand, have an albedo of 50 - 90 %. When the ice and snow areas grow, the global albedo increases. More radiation is reflected, so the Earth absorbs much less energy and continues to cool. The formation of ice and snow increases, which in turn increases the albedo. Climate scientists argue about whether our planet has experienced periods of complete glaciation at all throughout its history. According to the Snowball Earth hypothesis, this should have been the case about 750 to 600 million years ago. It is assumed that volcanism with enormous amounts of emitted CO₂ and the associated enhancement of the greenhouse effect freed the Earth from its ice cover again. Of course, this feedback effect can also run in the other direction. Melting ice and snow reduce reflectivity and thus increase the warming of the ground, air and water, which further accelerates the melting process. This is what currently happens.

3. The Earth's Climate System

53

1.

The exchange of energy from the ground to the atmosphere takes place via the emission of thermal radiation

2. Another form of energy release, latent heat, occurs through the evaporation of water at the Earth's surface

With dry soils less energy extraction and fewer clouds

Irradiation on the ground is increased and it becomes drier and drier

The surrounding soil and air are supplied with energy for evaporation deprived of water

Pedosphere and Lithosphere The Earth's soils and rock layers (pedosphere and lithosphere) exert another significant influence on climate through plants and gas and water exchange with the atmosphere. The exchange of energy between the ground and the atmosphere takes place via the emission of thermal radiation. How much energy is absorbed from solar radiation and emitted in the form of thermal radiation depends on the nature of the ground surface. Dark surfaces absorb more solar radiation, bright surfaces reflect more radiation. Another form of energy transport occurs through the evaporation of water on the ground. During the evaporation of water, energy is extracted from the surrounding soil and air, which reaches the atmosphere with the rising water vapor and is released again there during condensation in the clouds. This is referred to as latent heat. When the ground is relatively dry, less latent heat can be released to the atmosphere. Less evaporation also allows less energy to escape, resulting in a higher temperature of the ground. Since less water vapor also enters the atmosphere, fewer clouds form, and radiation to the ground is increased - the ground becomes even warmer and drier, and a reinforcing feedback begins.

3. The Earth's Climate System

55

The influence of the biosphere on the climate is determined by the gas exchange with the atmosphere

Evaporation from plant surfaces increases the water cycle

In addition, vegetation changes the albedo of the soil surface and thus influences the energy balance

The gas exchange is mainly determined by the carbon cycle

Development of the Atmosphere Originally, the atmosphere consisted mainly of CO2, N₂, methane and water vapor

Photosynthesis of primitive algae later led to O2

The biosphere still has a strong influence on the greenhouse effect, as plants constantly remove CO2, from the atmosphere

The concentration of the greenhouse gases methane and nitrous oxide is also controlled by the biosphere

The Role of the Biosphere The influence of the biosphere on climate is determined by gas exchange with the atmosphere, primarily by the carbon dioxide cycle. Originally, the Earth's atmosphere consisted mainly of water vapor (H₂O), methane (CH₄), nitrogen (N₂) and carbon dioxide (CO₂). Single-celled organisms in the primordial oceans gradually added free oxygen through photosynthesis and, after the formation of an ozone layer in the stratosphere, enabled the development of more highly developed life on the continents. Even today, the climatic importance of the biosphere lies primarily in its influence on the chemical composition of the atmosphere and thus on the strength of the greenhouse effect. Through photosynthesis, plants constantly remove carbon dioxide from the atmosphere. The concentration of methane and nitrous oxide, which also act as greenhouse gases in the atmosphere, is also controlled in part by processes in the biosphere. The greenhouse gas methane is produced naturally primarily by the anaerobic decomposition of organic material (e.g., in swamps and bogs), and the production of nitrous oxide is strongly influenced by the activity of bacteria in soil and water. In addition, plants on the Earth's surface reduce the albedo.

3. The Earth's Climate System

57

N

The term CLIMATE is derived from KLINEIN, the Greek word for INCLINATION

23,4 °

S

The seasons are a consequence of the INCLINATION of the Earth’s axis relative to the orbital plane of the Earth around the Sun

SUMMER IN THE NORTHERN HEMISPHERE

WINTER IN THE NORTHERN HEMISPHERE

The inclination causes the NORTHERN HEMISPHERE to be more intensely irradiated by the Sun

Only certain planets in the solar system have seasons, depending on their inclination

Six months later, the SOUTHERN HEMISPHERE is irradiated more intensely by the Sun

Mercury 0,1°

Venus 177°

Earth 23°

Mars 25°

The Emergence of the Seasons The irradiation of the Sun determines our climate. The word “climate” is derived from klinein, the Greek word for “inclination”. The phenomenon of the seasons is a consequence of the inclination of the Earth's axis by 23.5° with respect to the orbital plane of the Earth and the other planets (ecliptic) around the Sun. This inclination of the axis means that during the northern summer the Northern Hemisphere is tilted towards the Sun and thus receives more solar radiation, while the Sun's rays fall more obliquely on the southern hemisphere and are distributed over a larger area. Six months later, the southern hemisphere is irradiated more intensely, and winter prevails in the northern hemisphere. The stability of the Earth's axis is crucial for a temperate climate. The Moon, which was formed by the Earth's collision with a protoplanet (see p. 11), is responsible for this stability. Without our satellite, the axis would be unstable, the Earth would tumble, and the climate would change drastically. The planets in the solar system have rotational axes that are inclined at different angles. Both Earth and Mars have seasons, while Venus and Mercury do not because their rotational axes are perpendicular to the ecliptic.

3. The Earth's Climate System

59

Due to the spherical shape of the Earth, the tropics receive higher solar radiation than the polar regions

Therefore, the mean temperature is highest around the equator and decreases towards the poles

W O

The climate zones extend in an east-west direction around the Earth and have common features due to the climatic conditions

CLIMATE ZONES Polare zone Dry zone Temperate zone Continental zone Tropical zone

Temperature, precipitation, solar radiation, etc. play an important role in the classification of climatic zones

The Formation of Climate Zones One consequence of the spherical shape of the Earth is that the average temperature over the course of the year is highest in the equatorial region and decreases toward the poles. The different angles of incidence at which the Sun's rays hit the Earth's surface are also the reason why there are different climatic zones on Earth. A climate zone is a group of areas that extend in an east-west direction and share common characteristics (e.g., vegetation) due to their climatic conditions. In the tropical zone, for example, it is warm and humid all year round. Depending on the location, one can find tropical rainforests as well as tropical steppes and deserts. There are few distinct seasons because the Sun is perpendicular above the equator twice a year. In the tropics, temperatures can vary more within a day than the daily fluctuations throughout the year. In the temperate zone, on the other hand, the different seasons are much more pronounced. In the interior of the continents, it is dry and coniferous, deciduous and mixed forests grow. In the polar regions, solar radiation ranges from flat to almost nonexistent throughout the year, and it is therefore much colder on average. The vegetation is much less lush with grasses and low shrubs. Characteristic of this zone are the several months of polar days in summer and the several months of polar nights in winter.

3. The Earth's Climate System

61

POLAR ZONE The temperature rarely exceeds zero degrees and solar radiation is reduced

CONTINENTAL ZONE Regions with warm to cool summers and very cold winters

TEMPERATE ZONE Climate from mild maritime to continental climate with high temperature fluctuations

DRY ZONE TROPICAL ZONE In the tropics it is hot and humid all year-round. The tropical rainforests are located in this zone

Climate zone where it is very dry due to the fact that moisture evaporates quickly from the air and there is very little precipitation

The Climatic Zones of the Earth The climate zones show the effects of the different energy supply to the Earth's surface. For example, the average angle of incidence of solar radiation, in the annual mean, influences the vegetation quite significantly. The additional energy flow to the Earth's surface, caused by the anthropogenic greenhouse effect, is gradually changing the position of the climate zones. They are shifting from the equator toward the poles - a development that most of the species specialized in their respective ecosystems cannot keep up with.

3. The Earth's Climate System

63

?

4. THE CLIMATE CHANGE Since the formation of the Earth around 4.6 billion years ago, there have always been strong climate fluctuations and major changes on the planet. But since the beginning of the Holocene period around 12,000 years ago, and thus since the last ice age, our climate has been relatively stable. However, a significant increase in mean atmospheric temperature has been observed since 1980. Climate researchers agree that the current climate change can only be explained by human activities.

1 0 -1

0

ΔGMST (°C)

-2 -4

Relatively stable

-6

Significant increase

Age (yr BP)

Source: osmanclimate.com © Springer-Verlag GmbH Germany, part of Springer Nature 2023 H. Lesch et al., Understanding climate change, https://doi.org/10.1007/978-3-662-66372-1_4

0

500 250

75 0

0

2,

4,0 0

6,

8,

000 10,

 12,

 14,

 16,

18, 

 20,

22,



-8

ΔGMST (°C)

GLOBAL MEAN SURFACE TEMPERATURE (GMST) EVOLUTION OF THE LAST GLACIAL MAXIMUM TO PRESENT

The more greenhouse gases in the atmosphere, ...

... the more thermal radiation is absorbed by the gases, ...

Deviation from the 1961-1990 average in °C

DEVIATION OF THE GLOBAL AIR TEMPERATURE +1.0 +0.8 +0.6 +0.4 +0.2 0 -0.2 -0.4 -0.6 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2 2010 2020

Source: umwtbundesamt.de

There is a consensus that climate change is predominantly man-made (over 34,000 publications)

... the more thermal radiation is remitted towards the Earth

Steeply rising global warming

Man-Made Climate Change The current consensus among scientists is that the concentration of greenhouse gases in the atmosphere, particularly carbon dioxide, has strongly increased since the Industrial Revolution. As we have seen, greenhouse gases play a key role for the mean temperature and at the same time for the habitability of our planet, because these gases absorb the heat radiation of the Earth's surface and partially radiate it back towards the Earth. The more greenhouse gas molecules there are in the atmosphere, the more heat radiation is radiated back toward the Earth. Since the atmosphere as a whole envelops the Earth, the increase in greenhouse gases undoubtedly leads to global warming. In fact, as worldwide observing stations show, the global temperature of the Earth has risen since the industrial revolution, from about 1850 until today. This is clearly visible in the measured deviations from the mean value (shown in the sketchnote on the left). These deviations have increased continuously, especially since the 1970s.

4. The Climate Change

67

Carbon dioxide in particular plays a crucial role in the anthropogenic greenhouse effect

However, s in Revolution ce the Industrial , con increased centrations have by more t han 40 % from abou t 280 ppm 416 ppm to to over day

of years, s d n a s u o h For t tent in the n o c CO2 e th ere was h p s o m t a Earth's parts per 0 0 3 w o el b always ) million (ppm

CARBON DIOXIDE CONCENTRATION IN THE ATMOSPHERE Carbon dioxide concentration in ppm

480 440 400 360

Data from current measurements and reconstructed from ice cores

← today ← 1950

320 300 280 240 200 160 800,

700,

600,

500,

400,

300,

200,

100,

0

Years before present (0 = 1950) Source: clima.nasa.gov/evidence lked up Mar 15th, 2020

1 Cubic centimeter air = 10²⁰ Air particles = 10¹⁶ CO2 molecules

Concentration of Carbon Dioxide in the Atmosphere The main reason for this anthropogenic or man-made greenhouse effect is that humans burn carbonaceous fossil fuels to produce usable energy, releasing carbon dioxide in the process. Initially, this occurred mainly in Europe and North America, and later globally. Over the past four generations, annual CO₂ emissions have increased from 2 gigatons in 1900 to 36.4 gigatons in 2019 - the highest level ever recorded to date. Ice core samples show that the CO₂ content in the Earth's atmosphere has always been below the 300 ppm mark over thousands of years. The abbreviation ppm here stands for parts per million, i.e. the number of CO₂ molecules per million molecules of dry air. However, since the Industrial Revolution in the 1800s, the concentration has increased by almost 50 % from about 280 ppm to over 416 ppm today, and is higher today than at any other time in the last 800,000 years. Anyone who thinks that 416 CO₂ molecules per 1 million air molecules is too few particles to cause such dramatic changes should think again and emphasize that there are 10²⁰ air particles in one cubic centimeter of air, 10¹⁶ of which are carbon dioxide molecules. That is a large amount.

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What about the objection that the variations of sunspots, with their increased radiation levels would be responsible for the measurable temperature increase of the last four decades?

The solar activity decreases while temperature and carbon dioxide content in the atmosphere increase

Temperature anomaly in °C

Temperature  Sunspots

+0.4 +0.2

420 400

0.0

380

-0.2

360 340

-0.4

320

100

Number of sunspots

The temperature rise does not correlate with the solar activity, but does correlate with the CO2 concentration

+0.8 +0.6

300

75

280

50 25 0

1860

1880

1900

1920

1940

1960

1980

2

Carbon dioxide concentration in ppm

TEMPERATURE, CARBON DIOXIDE AND SUNSPOTS

2020

Year Source: Wikipedia

Solar activity and global warming are decoupled, and are currently even moving in the opposite direction

The Influence of Solar Activity Although the scientific evidence is clear, skeptics who doubt or even deny the anthropogenic greenhouse effect keep coming forward. The objection often raised by skeptics that the solar cycle, which is visible through the fluctuations of sunspots with correspondingly increased and decreased solar radiation values, is responsible for the measurable temperature increase of the last four decades. This can be clearly refuted. Solar activity has decreased since the 2000s, while atmospheric temperature and carbon dioxide levels have increased. Solar activity and global warming are decoupled, and in fact they are moving in opposite directions. There is now a scientific consensus - also supported by measurements - that an increase in global temperature at the Earth's surface is to be expected due to the anthropogenic greenhouse effect. This is shown by simulations with climate models that include the known physical processes in the atmosphere and the ocean. Depending on the increase in greenhouse gas emissions, the scientists determined an average global warming of the Earth's surface of 0.9 to 5.4 °C by the end of the 21st century. This temperature increase refers to the comparative values from the end of the 20th century. Such a temperature rise would have catastrophic consequences for humans and nature if it were to occur.

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H I H-C-H I H

Methane concentration in ppb*

1950 1900

GREENHOUSE GAS METHANE (CH₄)

1850

Methane is a greenhouse gas that is 28 times more effective than CO2

1800 1750

Increase from 700 ppb (before industrial revolution) to almost 1900 ppb today

1700 1650

1888

1892

1996

2

2004

2008

2012

Year

2016

2020

*ppb = parts per billion

Source: en.wikipedia.org

?

37 % of global methane emissions are directly or indirectly attributable to livestock farming Source: umwtbundesamt.de

However, methane lasts only 10-15 years in the atmosphere, CO2 50-200 years

However, methane emissions could increase sharply as permafrost thaws

The Role of Methane in the Anthropogenic Greenhouse Effect The gas methane (CH4) also plays an important role in amplifying the greenhouse effect. Compared to carbon dioxide, methane has a 28 to 72 higher warming capacity, especially when considering the effect for the next 100 or 200 years. However, its concentration is lower by a factor of 200. Since the industrial revolution, the concentration of methane in the Earth's atmosphere has increased from about 700 ppb to over 1800 ppb today. Due to its structure, the methane molecule, like carbon dioxide, is a gas molecule that absorbs thermal radiation, causing it to vibrate, which increases its kinetic energy. Subsequently, the thermal radiation is emitted again. Livestock farming accounts for 37 % of global methane emissions, either directly or indirectly. Today, methane contributes about 16 % to the anthropogenic greenhouse effect. That's a quarter of the CO₂ effect, which is 66 %. This figure could soon rise sharply due to the thawing of permafrost in Siberia and Canada. Methane is a short-lived greenhouse gas; it remains in the atmosphere for about 10 years until it oxidizes and becomes CO₂, which then additionally warms the atmosphere for centuries.

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Humans contribute to the increased release of nitrous oxide, ... ... through nitrogen-based fertilizers

... through industrial production of chemicals

... through combustion of fossil fuels

Nitrous oxide concentration in ppb

NITROUS OXIDE (N₂O) 335 330 325

Nitrous oxide is a greenhouse gas that is 265 times more effective than CO2

320 315

Increase of 22 % from 270 ppb (1750) to 330 ppb (2017)

310 305 300 395 1975

1880

1985

1990

1995

2

2005

Year Source: wiki.bildungerver.de

2010

2015

2020

The Role of Nitrous Oxide in the Anthropogenic Greenhouse Effect Another greenhouse gas is nitrous oxide (N₂O, laughing gas), which has roughly 265 times higher warming capacity than carbon dioxide. In the Earth's atmosphere, the concentration of this gas has increased by about 20 % since the industrial revolution and today contributes about 6 % to the anthropogenic greenhouse effect. However, due to its low concentration, this corresponds to only 10 % of the CO₂ effect. The emission of N₂O occurs both naturally and through human influences: In nature, N₂O is released by bacteria in soil, water bodies and virgin forests. However, humans contribute to the increased release of this greenhouse gas through the use of nitrogen-based fertilizers, the industrial production of chemicals, and the burning of fossil fuels.

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Fluorinated greenhouse gases were artificially developed for use in industry (e.g. refrigerants)

The residence time in the atmosphere is several thousand years

Even though they account for only 1.5 % of emissions, their impact should not be underestimated due to their long residence time and high effectiveness

Fluorinated hydrocarbons are 12,000 to 25,000 times more effective than CO2

Nitrous Oxide 4.2  % Methane 6.1  %

Share of greenhouse gases in emissions

HPFCs 1.2  %

PFCs 0.03  %

Total: 907 million tons

Sulfur hexafluoride 0.5  %

 88.0  %

Source: German Federal Environmental Agency

Fluorinated Greenhouse Gases Fluorinated greenhouse gases also play a role. Unlike the afore mentioned gases, they are not formed in natural processes but were developed specifically for industry. Although their share of total greenhouse gas emissions from industrialized countries is very small, their impact should not be underestimated due to their long residence time in the atmosphere (possibly several thousand years) and their effectiveness as a greenhouse gas per molecule (12,000 to 25,000 times more potent than CO₂). At 11 %, they contribute almost twice as much to the greenhouse effect as nitrous oxide.

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Positive feedback processes Cause

... are effects that contribute to the amplification of their cause, i.e. in this case to a further increase in temperature

The natural systems respond to these changes with feedback effects

Effect

These effects are the real “crux” of climate change

By increasing greenhouse gases in the atmosphere, humans are interfering with a multi-layered, complex natural system

ELEMENTS THAT PLAY A ROLE IN THESE FEEDBACK PROCESSES - More water vapor in the atmosphere - Reduced albedo - Melting of the Greenland ice sheet - Desertification of the rainforest - Decline of northern coniferous forests - Thawing permafrost - Mitigation of marine biological carbon production - Decrease in the CO2 absorption capacity of seawater

Feedback Processes Feedback processes can be positive (amplifying) or negative (stabilizing). In the context of climate change, these are effects that result from the increase in global temperature and the change in climate, which are self-reinforcing and lead to a further increase in temperature. Such processes are the real crux of climate change. Natural processes in the interaction of atmosphere, seas and oceans, ice masses and biosphere have always existed in the course of the Earth's history. Depending on the distribution of land masses, volcanism and various astronomical parameters, the climate was constantly changing, so the change of climate is completely natural. However, the concentration of greenhouse gases has increased dramatically in recent decades due to anthropogenic influences. In the midst of an interconnected, multi-layered, and thus complex natural process, mankind is altering the boundary and initial conditions of the atmosphere through the depletion of fossil resources. Carbon that was sequestered deep in the soil hundreds of millions of years ago is being brought first to the Earth's surface through coal mining, oil and gas extraction, and finally to the atmosphere through combustion processes. All natural systems respond to this gradual change through feedback. We will now explain some of them.

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Water vapor is the strongest natural greenhouse gas

Water vapor usually remains in the atmosphere for only a few days and then returns to Earth as rain, but is constantly replenished by evaporation

Increased concentration of water vapor in the atmosphere enhances the greenhouse effect, which leads to greater warming of the Earth

Due to global warming, more water evaporates, and the hotter it is, the higher the absorption capacity

Water Vapor in the Atmosphere Invisible water vapor is the strongest natural greenhouse gas. However, it only remains in the Earth's atmosphere for a very short time, usually a few days, and then returns to the Earth as precipitation. It is completely replenished by evaporation. Unlike CO₂, water vapor is not a direct cause of human-induced enhancement of the greenhouse effect because the anthropogenic greenhouse effect does not result from increased emissions of water vapor. However, more water evaporates due to global warming, and the warmer the air, the more water vapor it can hold. Increased water vapor concentration in the atmosphere increases the greenhouse effect, which in turn leads to higher global warming, and so on. This effect can be observed, for example, on the surface of poorly insulated window panes in winter. When the warm and relatively humid air in the room cools down near the window, its ability to absorb water vapor decreases and the water condenses on the glass pane.

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Global warming is melting the ice on the Earth's surface, for example in the Arctic Ocean

When the sea ice melts, the sunlight is no longer reflected back into space by the highly reflective snow, but is absorbed by the dark sea

Reduced Albedo As explained in Chapter 2, about 30 % of the solar radiation that reaches the Earth is reflected back into space by bright surfaces such as clouds, ice, and snow. However, the reflectivity or albedo of the Earth's surface is changing due to climate change. Global warming is causing snow and ice surfaces to melt, for example in the northern polar region. Sunlight is no longer reflected back into space by glistening snow and ice, but, rather, warms the polar ocean and dark land surfaces which are now exposed and no longer covered by snow. The exposed surfaces and dark water then absorb more solar radiation, raising global temperatures and melting even more ice. A feedback process is set in motion. Melting sea ice does not initially cause sea levels to rise because the sea ice displaces exactly as much water as it would absorb after melting. But as the water warms due to global warming, it expands and sea level rises, in part because additional meltwater flows into the sea from the continents.

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In recent years, ice loss in Greenland has increased drastically as glaciers and meltwater flow into the sea

50 % due to 50 % due to glacial movement meltwater into the sea

The ice sheet, which is 3 km thick in places, loses height as a result

Its surface, now still in high layers of cold air, is sinking and thus is exposed to warmer temperatures

This further increases the melting

In addition, the meltwater at the bottom of the glacier acts like a lubricating film and accelerates the sliding of the ice into the sea The complete loss of the Greenland ice sheet would cause sea levels to rise by 7 m over centuries to millennia

Melting of the Greenland Ice Sheet In recent decades, ice loss in Greenland has increased sharply due to glaciers flowing into the sea and increased melting in summer. As a result, the ice sheet, which is three kilometers thick in places, is losing height in the long term. Its central surface, which is now still located in high and thus cold air layers, is sinking and is thus exposed to warmer temperatures. This, in turn, further intensifies the melting process. In addition, the increased meltwater at the bottom of the glacier accelerates the sliding of the ice masses into the sea, just like a lubricating film. Unlike sea ice, the complete loss of the Greenland ice sheet would cause a sea level rise of seven meters over centuries to millennia and, of course, contribute to a reduction in albedo. Here again a feedback process is set in motion. As the ice retreats, the white surface area decreases, and the exposed darker soil absorbs more heat, contributing to further global temperature increases.

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The rainforest transports a huge amount of water from the ground to the the clouds

Water is absorbed by the tree roots and transpired through the leaves

The water vapor rises, condenses over the forest and falls as rain down again

In the event of a loss, gigantic amounts of previously sequestered carbon would be released as CO2, further driving GLOBAL WARMING

If the rainforest is cleared, transpiration and thus precipitation decrease

Then less water is available to the forest, it becomes drier and the rainforest becomes a desert

Desertification of the Rainforest The rainforest is a huge water circulation pump. Huge amounts of water are absorbed by the roots of the trees and released into the atmosphere as water vapor through the leaves (transpiration). The water vapor rises, condenses in huge clouds, and rains locally back to the ground. About 75 % of the precipitation in the Amazon basin comes from locally generated clouds. Only 25 % of the water is brought in from the Atlantic Ocean with seasonal variations, which then flows back through the Amazon into the Atlantic Ocean. Deforestation could drive this cycle to a critical limit: The less the amount of water evaporated by forest, the drier the region becomes, and the less water is available to the forest. Converting the Amazon rainforest to drought-adapted seasonal forest or agricultural land would have a fundamental impact on the Earth's climate, since about a quarter of the world's carbon exchange between the atmosphere and biosphere occurs here. If lost, gigantic amounts of previously sequestered carbon would be released as CO₂, a greenhouse gas that would further drive global warming. Increasing use of the rainforest can turn this carbon sink into a carbon source - a tipping point that is truly within our control. The fact that there have been more and more fires there in recent years makes the situation even more dramatic because the fires are pumping carbon dioxide into the atmosphere, and global warming is intensifying.

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With climate change, the numbers of plant pests, fires and storms are rising significantly

The northern coniferous forests cover almost one third of the world's forest area

Water scarcity, evaporation and human use affect the regeneration

Massive release of carbon dioxide, resulting in accelerated global warming

The disappearance of forests would destroy the habitat of many animals and plants

When characteristic thresholds are exceeded, forests are threatened with displacement by scrubland and grassland

Decline of the Northern Coniferous Forests The northern coniferous forests cover almost one-third of the world's forest area. Due to climate change, their exposure to plant pests, fire and storms is already increasing significantly. At the same time, water scarcity, especially in the growing season, increased evaporation and human use are affecting forest regeneration. When pollution exceeds critical thresholds, forests are displaced by scrub and grasslands. The disappearance of forests would not only destroy the habitat of many animals and plants, but would also mean a massive release of carbon dioxide, which will contribute to accelerated global warming.

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nadian a C d n erian a everal b i S e h In t rost, s ns of f a m r e o p illion t ably b d e r hund resum ore p e r a carbon depths of m at s stored three meter than

ost

afr

When permafrost thaws, large amounts of the greenhouse gases carbon dioxide and methane are released into the atmosphere

rm Pe

rm Pe

ost r f a

The carbon comes from organic material mostly deposited before the last ice age

Thawing Permafrost Several hundred billion tons of carbon are presumably stored at depths of more than three meters in the Siberian and Canadian permafrost. They come from organic material that was deposited here mostly before the last ice age. When permafrost warms, it releases large quantities of carbon dioxide and methane, which are greenhouse gases, into the atmosphere. Permafrost soils contain more carbon than is currently present in the atmosphere. If the permafrost layers are thawing, i.e. if the carbon also pushes to the surface from greater depths, the atmosphere will develop into a hot-temperate atmosphere. The consequences for mankind would be incalculably catastrophic.

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Very IMPORTANT for the climate

PEATLANDS

WET PEATLAND ... stores huge amounts of carbon

BUT

... emits the greenhouse gas CO2

Peatlands store twice as much biomass

Forest occupies 10 x more area than peatlands Forest

DRAINED PEATLAND

TH AL

G OU

H

Moors

REWETTING the peatlands is an urgent task

95 % 95 % of the moors in Germany are drained CO2

They emit more than 5 % of greenhouse gases → more than flights

Drained Moors Peatlands are important components of the climate system because they store and bind enormous amounts of carbon. Twice as much carbon is stored in our planet’s peatlands as in all the world's forests, even though they cover only one-tenth of the surface area. This has had a climate-cooling effect over the last 11,000 years. Bogs are wetlands with a constant surplus of water. Plants that absorb carbon settle in the moist bog soil. When these die, they decay very little because of the low oxygen supply in the bog soil. The dead plants then form peat, in which the carbon of the dead plants is stored. In the past, the peat was used as heating material. In the process, the carbon burned to CO₂. When peatlands are drained, aeration of the peat body occurs. As aeration takes place, the carbon previously stored over many thousands of years oxidizes to carbon dioxide and escapes into the atmosphere within a very short time. In addition, the greenhouse gas nitrous oxide is produced in the more nutrient-rich peatlands. More than a third of all agricultural greenhouse gas emissions come from drained peatlands, and in Germany they are responsible for over 5 % of all greenhouse gas emissions. The rewetting of drained peatlands is therefore an important task.

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The world's oceans absorb large amounts of carbon dioxide, making them increasingly acidic

Dead marine life sinks into the depths, storing carbon in the sediments

Algae form the basis for the entire oceanic food chain ification Warming and acid CO2 of water reduces re uptake, leaving mo carbon dioxide in the atmosphere

Around 40 % of previous anthropoge nic CO2 emissions w ere thus removed fr om the atmosphere

The CO2 is dissolved in the seawater and is used to a large extent by algae to grow

Weakening of the Marine Carbon Pump The world's oceans absorb enormous amounts of carbon. Around 40 % of anthropogenic CO₂ emissions to date have been removed from the atmosphere in this way. A large part of this is used by algae for growth. After dying, they sink into the depths and store the carbon in this way. This function will be significantly reduced by further warming and acidification of the water, as well as more frequent oxygen removal, leaving more CO₂ in the atmosphere. This will also further increase the warming of the atmosphere. This in turn will also further increase the temperature of the oceans. But since the ability of water to absorb carbon dioxide decreases as the water temperature rises, the CO₂ concentration in the atmosphere also continues to increase - a vicious circle that could make the Earth an uninhabitable planet for humans.

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TIPPING ... means that changes occur that can no longer be stopped, i.e. are irreversible

TIPPING POINT Critical threshold at which a small change qualitatively alters the state or evolution of a system

These feedback processes become particularly important when certain temperatures are exceeded

Climate ults e res g n a ch cesses o r p n i re that a rcing einfo r f el s

Feed

lification

EFFECT

Am p

back

This means that a progressive increase in temperature can lead to a cascade of mutually triggering tipping points (domino effect)

CAUSE

At these tipping points, small changes can cause the Earth system to transition to a qualitatively new state

Tipping Points In the climate system, the various components often interact via positive (destabilizing) and negative (stabilizing) feedbacks. Over a longer period of time, the positive and negative feedbacks balance each other out, and the climate remains in a more or less stable state of equilibrium. At certain times, however, the positive, self-reinforcing feedbacks predominate. This is particularly evident when certain temperatures are exceeded. At these thresholds, small changes can cause the Earth system to transition to a qualitatively new state. This is referred to as a tipping point. Tipping point means that these changes develop a dynamic that can no longer be stopped, i.e. is irreversible. The phenomenon of such tipping processes also plays a role when certain feedback effects are considered in isolation. This means that a progressive rise in temperature can lead to a cascade of mutually triggering tipping points (domino effect). However, we do not perceive this tipping immediately. It happens in “slow motion” according to human time scale. We only really feel it when it has happened, and then it's too late.

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TIPPING ELEMENT ... associated with a particular region Collapse of the Arctic sea ice

Melting of the Greenland ice sheet Slowdown of the North Atlantic Current Collapse of the Amazon rainforest More violent El Niño events

GREENLAND

ARCTIC

NORTH ATLANTIC CURRENT

Collapse of the northern coniferous forests

NORTHERN FORESTS

PERMAFROST

INDIAN SUMMER MONSOON

SAHEL-ZONE AMAZON RAINFOREST SEA

EL NIÑO

WEST ANTARCTIC

Melting of the West Antarctic Ice Sheet

Bistability of the Sahel: first greening, then significantly drier

Methan

Thawing of the Siberian and Canadian permafrost Weakening or strengthening of the Indian summer monsoon Disruption of the Arctic food chain and massive coral mortality

Tipping Elements in the Climate System of the Earth Global warming sets in motion natural processes in the various elements of the Earth's climate system. Particularly problematic are the processes that are self-reinforcing. For example, global warming leads to more evaporation of water, and since water vapor is a greenhouse gas, this increases the temperature of the atmosphere, which in turn leads to increased evaporation of water. Because of these self-reinforcing feedback processes, when a certain threshold is exceeded, the Earth's climate system can enter the uncontrollable state of a hot season. The environmental impacts of tipping points are far-reaching and could threaten the livelihoods of many millions of people. The latest models of the habitability of our planet with further warming lead to dramatic scenarios. Large parts of the globe around the equator would become completely uninhabitable. It is the combination of human-induced trigger mechanisms and nature's responses to those triggers that form an infernal duo. We are driving nature to conditions and effects that would not exist without our intervention.

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Natur al CO2

Natur al CO2

Additional CO2

5. EFFECTS OF CLIMATE CHANGE Through the actions of humans there is an increase in the concentrations of carbon dioxide, methane, nitrogen oxides and other greenhouse gases. The resulting enhanced greenhouse effect is causing changes in temperature, precipitation, cloud cover, snowpack, and sea level, as well as significantly more frequent weather extremes. Some of these impacts are based on simple physics, such as sea level rise, ocean acidification or reduction of the albedo. Others represent nonlinear, complex consequences, such as changes in ocean currents.

© Springer-Verlag GmbH Germany, part of Springer Nature 2023 H. Lesch et al., Understanding climate change, https://doi.org/10.1007/978-3-662-66372-1_5

In a 2019 special report, the IPCC projects that sea levels will rise 60 to 110 cm by 2100

Water occupies a larger volume at a higher temperature

Intergovernmental Panel on Climate Change (IPCC) 2019 Special Report on the Ocean and Cryosphere

REASONS FOR THE INCREASE

Another reason is melting ice on the continents Sea level rise is a risk that poses a direct threat to many people

Sea Level Rise A steadily rising sea level is one of the risks that pose a direct threat to us humans. As a result of global warming due to the enhanced greenhouse effect, sea level has risen by 3.2 millimeters per year between 1993 and 2020. In other words, it has risen by almost seven centimeters since the beginning of this century. In its Special Report “Ocean and Cryosphere SROCC” (2019), the Intergovernmental Panel on Climate Change (IPCC) projected that the sea level will rise by an average of about 84 centimeters this century if anthropogenic emissions of greenhouse gases continue unabated. Even if we significantly reduce these emissions and keep the temperature rise below 2° C by 2100, the sea level will rise by about 43 centimeters. From observations between 2005 and 2017, the contribution of this thermal expansion to sea level rise was estimated at 40 %. The remaining rise is mainly due to melting ice on the continents: Greenland ice sheet mass losses (24 %), mountain glacier melting (23 %), and Antarctic ice sheet losses (13 %). Current measurements of the melt rate clearly indicate that the continental ice sheets are melting much faster than previously thought. The reason for this is that the ice on the surface melts unevenly and streams of water form, creating a liquid sliding layer between the ice and the ground at the base of the glacier. On this water slide, the huge sheets of ice flow faster into the sea.

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A massive rise in sea level would result in catastrophic flooding, especially for low-lying coastal regions

This affects many coastal cities, as 22 of the world’s 50 largest cities are located on a coast and are among the most densely populated areas on the planet

BREMERHAVEN HAMBURG GRONINGEN BREMEN

WILHELMSHAVEN

AMSTERDAM ROTTERDAM

Schematic representation of the land recession (light blue) with a sea level rise of 7 m in the coastal regions of Germany and the Netherlands

Implications for the Coastal Regions The forecasts up to the year 2100 provide us with an idea of what lies ahead for mankind; this is shown by a comparison of temperature and sea level in recent Earth history. The Greenland ice sheet holds so much water that a complete melting of the ice would result in a global sea level rise of seven meters. If the West Antarctic ice sheet melted, the sea level would rise by another 3.5 meters. If the East Antarctic ice sheet, previously considered largely stable, also melted and drained into the sea, the sea level would rise by more than 55 meters. However, the complete melting of the Greenland ice sheet would take many centuries and that of the Antarctic ice sheet many millennia. Worldwide, this would lead to catastrophic flooding, especially in low-lying coastal regions and cities. These include the most densely populated areas on Earth: 22 of the world's 50 largest cities are located directly on the coasts, including Tokyo, Shanghai, Hong Kong, New York and Mumbai. In Bangladesh, 17 % of the country's land area, with a population of about 35 million people, is now less than one meter above sea level. The coastline of Europe would change forever. Cities such as Rotterdam, Amsterdam, Groningen, Wilhelmshaven, Bremen, Bremerhaven and Hamburg would disappear from the map in this scenario. In the Republic of Kiribati, an island nation in the Pacific, the government is already taking measures to relocate its more than 100,000 inhabitants.

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g also n i m r a w eGlobal aching cons f r-re ply o has fa for the sup for s r quence rinking wate clean d ny people ma

With a tempe rature incre ase of 4 °C, the retreat of t he glaciers in t he Himalaya s would affect a r o u nd a quarter of C hina's popula tion and some 30 0 million peo ple in India from water shortages Himalayas

2 billion rranean In the Medite uthern the so region and in a, the drinic r f A f o s a e ar ould also w ly p p u s r te king wa stricted e r y el r ve e s be

Around two billion people worldwide would suffer the consequences of recurring dry periods and drought

Effects on the Water Supply Global warming naturally also has far-reaching consequences for the drinking water supply of many people. The retreat of the giant glaciers in the Himalayas would affect around a quarter of China's population and around 300 million people in India, if temperatures rise by 4 °C. In the Mediterranean region and in the southern areas of Africa, drinking water supplies would also be severely restricted. Around 2 billion people worldwide would suffer the consequences of recurring periods without rain, extended dry periods and drought. Water shortages make agriculture more difficult and jeopardize food supplies in the long term. If this rapid development is not halted, hundreds of millions of people will have to permanently leave their home regions to find better, more suitable living conditions elsewhere. A reliable supply of potable water could also become scarce in large parts of Europe. In Spain and southern Italy, groundwater levels have already dropped to catastrophically low levels. By 2070, the IPCC predicts that up to 44 million Europeans will be affected by water shortages. Rivers in central and southern Europe would then carry up to 80 % less water. To solve the water supply problems, partnershipbased, intergovernmental management of rivers and lakes, crossing national borders is proposed.

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CHANGES In other regions, higher water vapor content increases cloud formation and precipitation Hot dry air increases erosion in some regions EFFECTS

Weather extremes, heat waves with considerable damage to flora and fauna

Heavy rain with sudden flooding

Effects on the Atmosphere Global warming increases water evaporation in the oceans enormously. Basically, increased water vapor concentration amplifies the greenhouse effect and warming, so that even more water evaporates. All climate scenarios show that the global water cycle intensifies at higher temperatures. The atmosphere already responds very quickly to changes in temperature, pressure and humidity. Increased humidity and condensation add more energy to the atmosphere. The more energy added to the atmosphere by evaporated water, the more dynamic and rapid changes in the atmosphere occur. This increases the likelihood and severity of extreme weather events such as thunderstorms, hail storms, and even hurricanes. Hot, dry air will increase erosion in some regions, and higher water vapor content will increase cloud formation and precipitation in others. Weather extremes, heat waves with significant damage to flora and fauna, and heavy rain events with sudden flooding will have catastrophic effects on people. Such events can already be observed in many places around the world.

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Melting ice and snow reduces the reflectivity

In addition, the melting ice and snow reduces the reflectivity More solar radiation is absorbed by the ground or water

Effects on Cryosphere, Pedosphere and Lithosphere As already described in chapter 3, the cryosphere plays an important role in the global radiation budget of the Earth. It interacts with the ocean and the atmosphere. Of particular importance for the global energy budget is the significantly higher reflectivity of ice and snow (albedo) compared to soil and water. When white ice melts into darker water or darker soil, the warming of the ice surfaces is also increased because more and more energy is absorbed with less and less being reflected into space. Since the cryosphere is very sensitive to climatic changes, it is an excellent indicator of global warming. However, the frozen ice masses are not just a passive indicator of climate change. Rather, changes in the cryosphere have a significant impact on physical and biological systems. For example, they have a significant impact on the Earth's energy balance due to their physical properties such as albedo, thermal conductivity, and latent heat. Ice sheets and glaciers largely control the height of global sea levels, influencing ocean circulations. Loss of sea ice has far-reaching consequences for marine and terrestrial ecosystems. Finally, yet importantly, the cryosphere on the continents is an important freshwater reservoir on which millions of people depend, as we see, for example, in the Andes and Central Asia.

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NCTION I T X E S SPECIE rming, a w l a b lo With g ecies p s l a m i n a plant and ing extinct m are beco

due to forest fires

Due to drought by the shifting of climatic zones by changing ecosystems DISAPPEARANCE OF CO2 SINKS Less CO2 is absorbed by photosynthesis and is converted to O2

Effects on the Biosphere The climatic importance of the biosphere lies primarily in its influence on the chemical composition of the atmosphere and thus on the strength of the greenhouse effect: by means of photosynthesis, plants constantly extract carbon dioxide from the atmosphere and store it in their biomass. With global warming, more and more plant and animal species are becoming extinct. This happens due to the shifting of climate zones, the change of ecosystems, drought and forest fires. This causes the disappearance of these very important carbon dioxide sinks. Much less CO₂ is then absorbed through photosynthesis and converted into O₂. At the same time, water scarcity, increased evaporation and human use impair forest regeneration. The disappearance of the Amazon rainforest would have a fundamental impact on the Earth's climate system: after all, this is where about a quarter of the global carbon exchange between the atmosphere and the biosphere takes place. The disappearance of the forests would not only destroy the habitat of many animals and plants but would also mean a massive release of carbon dioxide, which could contribute to accelerated global warming.

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113

oceans e h t , y a d To r over still buffe al lob 90 % of g y warming b heat absorbing g in and dissolv e xid carbon dio

If the partial pressure of CO2 in the Earth's atmosphere is higher than in the ocean, the surface water binds carbon dioxide CO2 CO2

CO2

Warmth

However, the warmer the water, the higher the partial pressure of CO2 in seawater CO2

So an increase in temperature of the oceans leads to a higher concentration of CO2 in the atmosphere

This means that a warmer ocean can absorb less carbon dioxide from the atmosphere than an ocean with lower temperature

Ocean Acidification Perhaps it should be mentioned in this somewhat apocalyptic sounding chapter that the ability of water to absorb gases decreases as temperatures rise. Today, the oceans still buffer over 90 % of global warming by absorbing heat and dissolving atmospheric carbon dioxide. In the future, that will become much less. Whether seawater absorbs or releases CO₂ from the atmosphere depends on the difference in CO₂ partial pressure (partial pressure is the proportion of CO₂ to the total pressure in a gas mixture). If the pressure of carbon dioxide in the Earth's atmosphere is higher than the CO₂ partial pressure in the ocean, the surface water of the ocean will take up carbon dioxide. However, the partial pressure of CO₂ in seawater is strongly dependent on its temperature. The warmer the water becomes, the higher the partial pressure of carbon dioxide. The consequences are clear: a warmer ocean can absorb less carbon dioxide from the atmosphere than an ocean with a lower temperature. An increase in ocean temperature therefore inevitably leads to a higher concentration of CO₂ and thus to further warming of the oceans - a vicious circle.

5. Effects of Climate Change

115

6. WHAT CAN I DO? If there is one thing that emerges clearly, unequivocally and beyond doubt from climate research and the climate conferences around the world, it is this: we must phase out all activities that release greenhouse gases as quickly as possible. That is the scientific consensus. However, business and politics are clearly too slow in their efforts to reduce carbon dioxide emissions. But the guidance from research is clear; the next two decades will determine whether we can still achieve the important turnaround. Nature will respond to actions that are taken too late and too slow with rising temperatures that will pose a massive threat, endangering the prosperity of all our lives and life as we know it. Therefore, it depends on all of us - on each and every one of us!

© Springer-Verlag GmbH Germany, part of Springer Nature 2023 H. Lesch et al., Understanding climate change, https://doi.org/10.1007/978-3-662-66372-1_6

To this end, greenhouse gas emissions must urgently be reduced and with immediate effect

GOAL Significantly below 2 °C, preferably not more than 1.5 °C

The later the CHANGE starts, the less time we have

EMISSION SCENARIOS in line with the Paris climate goals

Economic interests in particular prevent implementation of the climate agreement in many cases

However, global consumption of coal, natural gas and crude oil continues to rise despite the climate protection efforts made by some countries

Emiion in Gt per year

2020 Maximum 800 Gt  budget 2016 Maximum 2020 2025 600 Gt  budget

50 40 30 20 10 0 1990.

2.

2010.

2020.

2030.

2040.

2050

Source: Spieg Online; The Global Carbon Project, Nature, Rahmorf

To achieve this goal, the global community must become greenhouse gas neutral in the second half of the century

Need to Act At the Paris Climate Conference (COP21), countries agreed to limit global warming to well below 2 °C, preferably to 1.5 °C. This is the only way we can still avoid triggering the cascade of tipping elements and making large parts of the Earth uninhabitable in the long term. In order to comply with this upper limit, greenhouse gas emissions must now be reduced, because the later the trend reversal begins, the less time we have. By 2020, the amount remaining to reach the 1.5-degree target has already shrunk to 420 gigatons (Gt) of carbon dioxide. If all known fossil energy reserves of natural gas, oil and coal were consumed, this would release around 5400 billion tons of carbon dioxide. The goal must therefore be to leave these raw materials underground and to convert our energy supply completely to renewable energies. It is clear that the global community must become greenhouse gas neutral in the second half of the century if this goal is to be achieved. But despite the climate protection efforts of some countries, global consumption of coal, natural gas and oil continues to rise. Above all, economic interests and a lack of penalty pricing for climate-damaging emissions are preventing the implementation of the climate agreement in many cases.

6. What can I do?

119

TRAJECTORIES OF THE EARTH SYSTEM IN THE ANTHROPOCENE Glacial - interglacial boundary cycle

Stability

Cycle of approx. 100,000 years

th is on r a E e h t ly t Curren a diabolic o t in y a w e th sed among u a c , e g a t o h n-made a m y b s g in h other t missions e s a g e s u o h green uction of r st e d e h t d an e the biospher

Holocene Anthropocene

e Tim Responsibility for the Earth Syem

Human emiions

Plan

Due to the impact of humans, the Earth system is on the verge of overturning

old

To stabilize the Earth's climate and prevent the activation of tipping points, we have little time left

By activatin g the tippin g points, the climatic con ditions would drift in to the uncontrollab le due feedback eff to ect

sh etary Thre Intrinsic fdba

Greenhouse Earth

Source: Wi Sffen et al.Proc. Nat. Academy of Sci.

If the Earth crosses the planetary stress limit at about 2 °C, the path cannot be changed due to feedback processes

There is Little Time Left Thus, if we take these resolutions seriously, we have very little time left to stabilize the Earth's climate and prevent the activation of tipping points beyond which climatic conditions on Earth would drift into the uncontrollable due to feedback effects. This was confirmed by climate scientists in the IPCC Sixth Assessment Report - AR6 of 2021. Over approximately the last 1.2 million years of Earth's history, relatively cold and warm phases alternated in a cycle of approximately 100,000 years (glacial-interglacial boundary cycle). Currently, our planet is on the path to a hothouse Earth, caused by humanity's greenhouse gas emissions and the destruction of biodiversity and many ecological systems, including deforestation, driven by intensive agriculture and industry. If the Earth crosses the planetary stress limit on this path at about 2 °C, the path can no longer be changed due to feedback processes. The path to an Earth that is on a stable path requires a fundamental change in the role of humans on the planet - but a determined and rapidly implemented reduction in greenhouse gas emissions is not enough. Improved forest, agricultural, and land management is also needed to sequester carbon in this way. In addition, biodiversity must be persisted, and technologies must be developed and deployed worldwide to remove carbon dioxide from the atmosphere and store it underground.

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121

A. Risks and consequences seem far away For many people, it is still unclear what climate change means for them. Climate change seems distant in time and space B. One's own influence is underestimated Others have the feeling that they cannot do anything on their own. This removes them out of their responsibility and the problem is delegated to politics

C. Habits

CO2

Deeply ingrained behaviors are a barrier to environmentally conscious action, and ingrained patterns of behavior are rarely challenged

EE COFF to GO

Psychological Hurdles to Climate Change Mitigation For many people, the causes and consequences of climate change seem far away, almost intangible. This so-called psychological distance is made up of various factors: the spatial distance, the temporal distance, the social distance and the degree of uncertainty. To counteract the great psychological distance in the case of climate change, it is imperative to focus attention on the local consequences of climate change. We feel its effects here and now. They are immediate, they are not pleasant, and therefore they can be frightening. In some cases, great fear can paralyze, especially when it is accompanied by the feeling that nothing can be changed anyway. However, if people have the impression that they can contribute to positive change through their behavior, i.e. if they experience self-efficacy, then even negative emotions can promote action. It is helpful to understand how one can take concrete action oneself as well as which climate-protecting behaviors are effective and which are not. Another hurdle that is closely related to perceived self-efficacy is the so-called responsibility diffusion. Beliefs such as “I can't make a difference through my behavior anyway because everyone else will carry on regardless” can mean that climate awareness does not lead to climate-friendly behavior. When this thinking is widespread and responsibility is passed on to others, collective passivity results.

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123

Formulate messages positively!

Therefore, the change of behavior should be positively motivated as a gain

... because for people, losses count about twice as heavily as gains

Example

RATHER

INSTEAD Driving less

Ride your bike more and stay healthy

The new behaviors can also be linked to other gains at the same time ... like more movement More examples Buy regional products, because they are fresher and richer in vitamins!

Become a (part-time) vegetarian, because it's healthy!

Invest your money in projects that support nature and other people

Positive Framing When it comes to the concrete measures and behavioral changes that are necessary for better climate protection, it is important that the corresponding messages are formulated positively. The necessary behavioral changes for each and every individual can also be understood as something positive, profitable, and not just as a loss of quality of life. In addition to the effect that the losses always outweigh the gains, there are also, quite generally, many positive aspects that accompany a corresponding change in life. Many of the necessary changes in life are associated with positive aspects for oneself, for example in terms of health. Driving less means more exercise, buying regional also means fresher and more vitamin-rich products, and giving up meat reduces the risk of cancer. Think positively: putting your commitment to fighting climate change into a new context will give you extra motivation. You just have to recognize the connection between changing your own behavior as a necessary contribution to mitigating climate change and the resulting benefits for yourself and others.

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The

Process

for

Motivated

This process is divided into several subprocesses 1.

Perception of a discrepancy between ideal state and reality

n

inatio Determ

Climate Engagement Many players continue to carry on with “business as usual”

ge

2.

Internalization of the situation through self-reflection

3. Triggering active action

Change is urgently needed!

Knowled

Questions - How can it be that so so little happens? - What can I do? - What needs to change?

Favoring factors

Empathy

Tipping moments

Self-efficacy Building a deep emotional connection

Realization that one's own contribution counts

All observations are translated into an action

Transformative Action Ultimately, however, it is also up to each individual to reduce emissions quickly. The process by which people become active is called transformative action. Transformative engagement takes place in several sub-steps. At the beginning of this process is the perception of a discrepancy between reality and what is seen as the ideal state. In the case of the process toward a motivated climate commitment, it is the realization that humanity is reaching global material limits for the first time in its history. Therefore, we must act. This realization is at odds with the reality in which many economic, political, and individual actors still continue on with business as usual. The next step is to internalize the situation, combined with a critical analysis. In the process, various questions can emerge that shed a critical light on the situation and lead to active action and behavioral change. What is important here are favoring factors that ultimately lead to action.

6. What can I do?

127

10 CLIMATE SAVER TIPS FOR REDUCING THE Tip 2 Avoid electricity from fossil fuels

Tip 1

Switch to an electricity provider offering 100 % green electricity at home

Drive & fly less Stay fit by walking or riding your bike and using public transportation Tip 10 Wash correctly Eliminate pre-wash and dryer & only wash full loads at just 40 °C instead of 60 °C 40 °

Save heat Better insulate your home and use modern Tip 9 heating & lighting technologies You don't have to be perfect, check what works for you

Tip 8

Ecological & ethical investment Let your invested money only work for things that are good for people and nature

FOR EVERYONE

Changed behavior can also be linked to other gains in the sense of a POSITIVE FRAMING

CO2 FOOTPRINT Tip 3

Eat less meat Tip 4 Become a part-time vegetarian. Change your It's healthy and uses food consumption much less resources Buy regional, seasonal and organic food. This is also soil and environmentally friendly

Tip 5

Heat according to plan If the temperature is reduced by only 1 °C, this already saves around 6 % energy Buy wisely Buy secondhand and used goods & repair & recycle

Check your car use Are the size, consumption and equipment appropriate or can the use of your car be eliminated altogether? Tip 7

Tip 6 However, individual behavior cannot replace political action

7. A LOOK AHEAD Our world already seems to be coming apart at the seams. With heat records, heavy rainfall events, droughts, persistent forest fires and forest dieback or the melting of the polar ice caps, we see that climate change is not in the distant future but is already having an impact on mankind today. Other phenomena such as the problems with the amount of plastic in the world's oceans, the extinction of species, the burning rainforest, factory farming, the onset of water scarcity or the ruthless exploitation of our planet's raw materials, combined with poisoned landscapes, also testify to the finite and delicate nature of our planet. But also exploding costs for housing, financial markets out of control, the ever-widening gap between rich and poor or the incipient rural exodus foreshadow an apocalyptic future for mankind. Our species is also threatened with extinction. It is therefore becoming increasingly clear that “business as usual” will not work. On the photos of the rising of the Earth, called “Earth Rise”, which we know since Apollo 8 from space, you can see our planet in all its beauty. Shouldn't we all do everything to ensure the survival of our civilization on this unique planet?

© Springer-Verlag GmbH Germany, part of Springer Nature 2023 H. Lesch et al., Understanding climate change, https://doi.org/10.1007/978-3-662-66372-1_7

1950

y toda

Compared to the past, there are many more people living on the Earth today, who also need much more space and resources

But what is a good indicator for this?

It can be used to measure how the life of a particular person affects the planet

That is, today the resources for each person have become scarcer

THE ECOLOG ICAL FOOTPRINT

It calculates how much forest, pasture, arable land and ocean area is needed to renew the resources consumed and absorb the waste products generated

The Ecological Footprint Today, nearly 8 billion people live on our planet, twice the number of just 50 years ago. And the Earth's population continues to increase. Not only is the number of people growing, but the space and resources a person needs on average are also growing, because our needs have also changed. For example, vacation trips by plane used to be a rarity. Today, they are more the norm. Families also rarely owned multiple cars. Or let's think about the progress of digitalization. In the past, a family usually had only one television. Today, there are usually several TVs in a household, plus computers, smartphones and tablets. To produce and operate all of these devices, energy and resources are needed. In addition, there are roads, airports, production facilities, retailing areas and much more. A good indicator that measures how a person's life affects the Earth is the ecological footprint. Developed in the mid-1990s by Mathis Wackernagel and William Rees, it indicates the extent to which the planet's ecosystem and natural resources are used. It calculates not only how much agricultural land a person needs for food, how many roads, factory buildings or shopping centers, but also, for example, how much forest is needed to reabsorb the CO₂ consumed for all these processes.

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133

What is it? On a certain day of the year, mankind has used up all the natural resources that the Earth can produce again within one year

Earth Overshoot Day 1970 - 2020 June 1 July 1 Augu 1 Sepmber 1 October 1 November 1

Source: Germanwat.org

More than one earth

Always sooner

Since 1970, our consumption of the Earth's resources has exceeded the capacity of our planet

The date moves forward continuously

Resources Consumption

Mankind currently lives as if it had 1.7 Earths at its disposal

2020

2010

2

1990

1980

1970

December 1

Earth Overshoot Day Earth Overshoot Day is calculated by dividing the ecological footprint made by all humans by the amount of biological resources the Earth can replenish in the same year. As humanity lives beyond its means and consumes more and more than can be renewed, Earth Overshoot Day moves forward in the year and in 2019 was already on July 29 worldwide. Analogously, it is also possible to calculate how many “Earths” would be needed annually to compensate for the use of resources. In 2019, this value was 1.74 Earths. Due to this development, the Earth has been in a resource deficit for many years. However, if we look at the individual countries, the picture is very different. The heaviest consumers Qatar and Luxembourg have already used up their resources for 2019 by mid-February, the USA by mid-March, and in the European Union the Overshoot Day 2019 was on May 10, in Germany on May 3. So we are not only living beyond our own means, but also beyond those of others. For the first time, however, the date was moved back in 2020, by a good three weeks, to August 22. To ensure that this is not a one-off effect, the economy must be consistently linked to sustainability in the future. Climate targets must be met, and resource consumption must be reduced.

7. A Look Ahead

135

Already in 1972 a group of scientists from MIT gave a warning with their model of the future »World3«

Humanity must respond to the new reality and make the necessary TURNAROUND

either RESULT or

Mankind is heading for a world-wide CATASTROPHE within 100 years

LONG-TERM TRENDS EXAMINED o Pace of population growth o Growth of food production o Growth in industrial production o Extent of resource exploitation o Pollution from development COLAPSE ???

MODEL Based on past data, the five long-term trends were used to “extrapolate” THE FUTURE

nd Sta

a

COLLAPSE

no un ( R rd

he ing t

)

limit

tors

grow

i

ndiv

fi th o

fac dual

t

Limi

Limiting the growth of all five factors

NO COLLAPSE

“Extrapolating” the Future As long as half a century ago, a group of scientists at the Massachusetts Institute of Technology (MIT) in Boston attempted to derive future trends using a cybernetic computer simulation. The model, called World 3, was developed on behalf of the Club of Rome under the direction of Dennis L. Meadows and Jørgen Randers to “project” the future based on five long-term trends using data from the past. The results were published in the book The Limits to Growth. The model considered 1.) the rate of population growth, 2.) the growth of food production, 3.) the growth of industrial production, 4.) the extent of exploitation of non-renewable resources, and 5.) the development of environmental pollution. The calculations showed that civilization will inevitably collapse if it simply continues to behave as it is, i.e. if all factors continue to increase. The scientists also tested scenarios in which some of the trends were brought under control. However, only the scenario in which the growth of all five trends was limited did not lead to collapse. The results of the study have been repeatedly reviewed and updated over the years and have never been refuted. It has also been shown that the five trends are developing essentially as predicted.

7. A Look Ahead

137

Can we establish a link between economic growth and climate change?

If the economic rate of change is REDUCED, the climate change will DECREASE

YES

When the economy GROWS, climate change ACCELERATES

The diagram shows

CO2 levels rose steadily with three exceptions, which were when the economy stagnated

Atmospheric CO2 measured at the Mauna Loa Observatory 420

2009 Slump due to the financial crisis Coapse of the Soviet Union in the early 1990s

380

38

360

34

Oil crisis 1973

340

30 26 22

320

Economic growth means climate change, more economic growth means more climate change

18 1960

1970

Source: esrl.noaa.gov

1980

1990

Year

2

2010

2020

 emiions in Gt/year

Conclusion

 connt in ppm

400

Economic Growth and Climate Change To stop climate change, carbon dioxide emissions must be drastically reduced. This is what was decided in the protocols of the Kyoto and Paris climate conferences. To measure the amount of carbon dioxide in the atmosphere with high accuracy, conditions must be perfect. This is the case at the Mauna Loa Observatory in Hawaii. The observatory is located far away from any civilization at an altitude of 3400 meters and has been continuously measuring the carbon dioxide concentration in the atmosphere since 1958, the International Geophysical Year. If we look at the measured curve, we see that it has risen continuously since measurements began. This is a depressing result, because it means that the efforts made so far to save carbon dioxide have not yet led to a reduction. However, a closer look shows that there are three small anomalies in the curve where the increase has slowed minimally. This occurred at times when there was a crisis situation with lower economic growth, so that the burning of fossil fuels was also reduced. The direct correlation between economic growth and carbon dioxide concentration becomes clear when the curve of global economic growth is compared with the curve of CO₂ emissions. These curves are almost congruent. From this, it can be concluded that only a different way of doing business and living can reduce raw material consumption and harmful emissions.

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139

In retrospect Industry has already made tremendous progress in recent years

However, ... the CO2, content in the atmosphere nevertheless has risen continuously

QUESTION Can climate change be combated by making processes MORE EFFICIENT so that they consume less energy? Why?

Conclusion As long as technical progress only leads to further economic growth, we will not be able to solve the problem of climate change

Saving energy through technical progress unfortunately often leads to producing more or even changing the whole system

Continue as Before, Only More Efficiently? After all, might it not be possible for more efficient methods of production and consumption to halt the rise in carbon dioxide concentrations? One approach to this is the idea of continuing to ensure economic growth, but without destroying the environment and without continuing to burn fossil fuels. Could this be achieved through more efficient processes that would result in less energy being consumed? However, if we look at the history of scientific progress, we find that the new technologies have often been more efficient and have consumed fewer resources. As a result, technological progress has usually not only compensated for the savings, but has even led to higher consumption. Thus, enormous advances in efficiency have already been achieved in the past, and especially in the last 30 years, but without any reduction in carbon dioxide emissions as a result. For example, car engines have become much more efficient in recent decades, but cars have become larger. Therefore, CO₂ emissions per kilometer have remained constant. It can therefore be concluded that we will not get climate change under control simply by making processes more efficient. As long as more efficient processes only result in the economy continuing to grow, increasing efficiency alone is not a means of solving the problem.

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141

What is geoengineering? This refers to methods designed to manipulate climate change

Distinguished are, ...

To avoid warming above 1.5 °C, we need to remove CO2 from the atmosphere

... Interventions to directly influence the climate system, e.g. Solar Radiation Management (SRM)

Goal of SRM: Increase of the reflection of the incident short-wave sunlight

... Projects for the reduction of CO2 in the atmosphere, e.g. Carbon Dioxide Removal (CDR)

How? BUT, ... Some geo-engineering approaches can be very dangerous

Removing CO2 from the atmosphere through natural carbon sinks or technical measures

GEO Engineering the Way Out? Geoengineering refers to technologies that artificially slow climate change. These methods vary widely, ranging from large-scale reforestation campaigns, to placing giant mirrors in space to shade the Earth, to technologies that capture carbon dioxide and store it permanently in underground reservoirs. In principle, a distinction is made between 1.) Interventions to directly influence the climate system, such as Solar Radiation Management (SRM) and 2.) CO₂ reduction projects, such as Carbon Dioxide Removal (CDR). SRM is about reducing the amount of short-wave sunlight reaching the Earth, and CDR is about removing some of the carbon dioxide back out of the atmosphere. Even if such methods are not currently available, it will still be necessary to remove CO₂ from the atmosphere in the future, because all climate models that assume warming up to a maximum of 1.5 °C have been calculated with the inclusion of such future technologies. However, some methods of manipulating the climate system are also very dangerous or have serious side effects. Therefore, geoengineering is not a solution to our problem. We have to stop CO₂ emissions.

7. A Look Ahead

143

Example t arre G m o r f Hardin On a common pasture everyone could drive their sheep

What happens when there are no rules? Thinking only of their short-term earnings, everyone put as many sheep as possible out to pasture

That is why overgrazing occurred

That means, a rule-free room ruins all

Current example So there should be rules of use in many areas The illegal clearing of the rainforests

The carbon dioxide that is released into the air

The overfishing of the seas

The overfertilization of soils

A CO2 price in a sufficient amount should be introduced

It Needs Rules Will we be able to solve today's problems with little or no intervention from the state, and is the thesis that the free market always extracts the greatest benefit for all true? Can we trust market-based instruments to regulate that our atmosphere is no longer used as a dumping ground for carbon dioxide and that the exploitation of resources is limited, overfishing of the oceans prevented or deforestation of the rainforests stopped? Unfortunately, however, there are no signs that business is taking this responsibility on its own initiative. It is still only focused on maximizing profits, producing goods as cheaply as possible and exploiting the Earth's resources to the maximum. The simple example in “The tragedy of the Commons” by American ecologist Garrett Hardin on the left side impressively shows that the predatory exploitation of individuals at the expense of all is the result of a space without rules. This can also be applied to today's problems. The state is called upon to create and enforce appropriate rules and measures in order to guarantee mankind a planet worth living on.

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145

We should ask ourselves what kind of world we would like to see

Doing nothing leads to disaster

w ne y eb ess er en Th awar

of n tio bility p um onsi ss A esp r CONTINUING AS BEFORE IS NOT AN OPTION

We must assume future-oriented responsibility

ing k ea its r B ab h

Courage of consumers to make conscious purchasing decisions

It's about having the courage to make changes

Courage of the media to report in a more differentiated way

Courage of companies to assume their responsibilities

Courage of politicians to set new rules

How Can We Rethink Our World? How do we finally get the CO₂ content in the atmosphere to fall instead of continuing to rise, and how do we solve all the other problems that are destroying our nature and making our planet an unfriendly place to live? In any case, something needs to be done very urgently - continuing as before is not an option! First of all, we should all ask ourselves as players, as consumers, i.e. every individual, whether politicians, managers in business or ordinary citizens, what kind of world we and our descendants want to live in. We have to face up to this responsibility and break with the old habits. Achieving these changes also requires courage, because it is usually not easy to wander off the beaten paths and work for a planet worth living on. This requires a large number of willing participants, because only together can we achieve this goal through our actions and decisions. In demand here are, for example, consumers, who can influence the necessary innovations with their purchasing decisions; the media, who can help shape opinions through differentiated reporting; companies and investors, who must become aware of their responsibility for a planet worth living on and initiate appropriate measures; the players in the education system, who must bring the knowledge content into schools, universities and textbooks and impart skills as well as content; and politics, which must set the rules by which we achieve this goal.

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If emissions continue unchecked, warming could exceed +4 °C by the end of the century

+4 °C +3 °C

Paris climate goal

Unlimited emissions

At the climate summit in Paris in 2015, it was decided to limit the global temperature increase to well below 2°C

However, current policies would lead to an increase of about 3°C by the end of the century

Current policy

+2 °C +1 °C

Warming already done

0 °C Source: Clima Action Tra­r

The 1.5-degree limit will be missed with the current policy

In order to implement the Paris target, countries around the world must quickly and drastically step up their climate protection efforts

What Does Politics Need to Do? If emissions continue to rise at this rate, our planet will have warmed by more than 4 °C on average by the end of the 21st century. Today, the warming is about 1 °C, and we are already experiencing dramatic effects. So it's time for something fundamental to happen, because the climate targets set at the 2015 UN climate summit in Paris cannot be achieved with current policies. The goal was to limit the temperature rise to 1.5 °C above pre-industrial levels. However, current policies are heading for an increase of about 3 °C by the end of the century. At such a rise, many tipping points will be reached, and it is questionable whether our planet will then still be livable. The carbon dioxide emitted also remains in the atmosphere for a very long time, and adaptions to reduce carbon dioxide emissions will have a very slow impact. The anthropogenic warming of the planet is a linear function of the total (cumulative) CO₂ emissions since the beginning of the industrialisation. Therefore, there is a limited CO₂ budget until we reach a 1.5°C warming. Each tonne above that will get us into trouble. That is why it is also important to act quickly, because any waiting means that our efforts will have to be even greater in order to reach the target. It is therefore very important that policymakers finally live up to their responsibility and that countries around the world drastically step up their climate protection efforts.

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149

Studies and practical experience show that it is possible to achieve rapid and drastic reductions in greenhouse gas emissions

Many of the technologies required for this already exist and some of them are even financially competitive in certain cases

Several countries have already reduced their greenhouse gas emissions in the years between 2005 and 2017

For example, Denmark or Great Britain

... were able to reduce emissions by more than a third

Numerous EU countries are already on their way in phasing out coal-fired power generation and will do so before 2030

Rapid Emission Reductions Are Possible Even though it may currently appear that the goal can only be achieved with very great effort and under drastic rules, the situation is not hopeless. Studies and practical experience show that the prerequisites for an immediate reduction in carbon dioxide emissions are in place. The necessary technologies are available and some of them are even competitive today. It is also to be expected that this development will generate further innovations. In addition, it can be assumed that the industries that address the problem now will also position themselves well for the future. There are major differences in the way this problem is tackled around the world. However, several countries have already reduced their greenhouse gas emissions in the years between 2005 and 2017. Numerous EU countries are leading the process and will phase out coal-fired power generation by 2030.

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THE ENERGY TURNAROUND is the transformation from a nuclear-fossil to a SUSTAINABLE industrial society STRUCTURAL CHANGE Exclusively RENEWABLE energies

pling of economic g u o c ro De

wt h

Industry

rce consu esou mpt r d i on n a Great transformation

Energy transition 100 % regenerative

Infrastructure

Resource turnaround 100 % recycling

Respect the planetary boundaries

Complete TRANSFORMATION of life & economy

Services

Lifestyle

Traffic

Scope for design for future generations

The Energy Turnaround The energy turnaround is the most important measure for climate protection in the fight against the consequences of global warming. In principle, the energy turnaround consists of a fundamental change from an industrial society that essentially uses fossil raw materials to a sustainable industrial society that uses only renewable energies. This requires a complete conversion of all industrial production chains, the service sector and also the private sector. This concerns energy sources, energy infrastructure and, above all, storage capacities for renewable energies. In addition to effective climate protection, this should also achieve a decoupling of economic growth and resource consumption overall. Together with the resource transformation and the expansion of the circular economy, the energy transformation will fundamentally change the economic and ecological conditions in our country. With this major transformation, we are respecting the planetary limits of energy and raw materials and giving future generations new opportunities to shape the future.

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153

2. 1.

We need to use energy more EFFICIENTLY and SAVINGLY

Expansion of offshore wind power New construction and repowering of onshore wind turbines

We need to switch completely to RENEWABLE energies, away from fossil fuels and uranium

In particular, with additional photovoltaics and wind power by 2030

Photovoltaics in combination with agricultural use

ENERGY TURNAROUND can reduce energy-related CO2 emissions to zero by 2035

3. For this we need ALL forms of renewable energies

Floating photovoltaics

More groundmounted photovoltaics

Photovoltaics on roofs and facades

How the Energy Transition Can Succeed The energy turnaround will entail a complete transformation of our energy supply. We need to switch completely to renewable energies and away from fossil fuels. Only the combination of wind power, solar energy, geothermal energy, biomass, hydropower and other renewable energies can lead the energy transition to success, with wind power and photovoltaics having the greatest potential. This means that the entire energy supply (mobility, industry, heat, agriculture, etc.) must be converted. Indispensable for this “Apollo program” are thousands upon thousands of technicians, engineers, i.e., people who work and research in the STEM subjects and thus ensure that the innovation potential for new technological solutions can be tapped and that the technical systems can be built and operated.

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Many political, industrial and individual stakeholders now see the urgent need for change

... because Business as usual is not an option

Now it depends on which steps we choose to move forward on this path Goal Goal Goal

Goal

We will achieve the goal if we act now and assume forward-looking responsibility

We have the ability and responsibility to make these changes

We Must Act! Many people have now realized that doing nothing and carrying on as before is not an option. This applies to large sections of the population, but also to politics and business, because “business as usual” would also change our world, but not for the better. It is now important that action is taken and that the right steps are planned and ultimately taken to handle this crisis. We have reached a limit globally, and structural changes are needed to successfully overcome this crisis. However, in addition to the decision-makers, this also requires each individual in their function, with their way of life, their commitment and their ideas. Many of us are also part of a networked system, whether at work, in our free time, in a position of responsibility or in a political party. Ultimately, we are all part of this world and we all live in it, love it and want to leave our children, grandchildren and great-grandchildren a world worth living in. That is why we will tackle this task together.

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Can my contribution really make a difference? We are all part of networked systems in which nothing happens without effect

I want to take responsibility, but what can I do?

We can all be part of the change Engagement is a good way to move from reactive defense to active action in a crisis

Change your lifestyle where possible Influence your immediate environment

Network and inform yourself politically

YOU WILL FIND YOUR WAY

And What is Your Path? On this last page, we as authors would like to address the question of how each and every one of us can contribute and take responsibility. So it's about the path you can take to get involved in this great task. It's about ideas and about commitment, but also about realizing that your own contribution counts. We can learn from each other, share our ideas and become active together. There are many ways to get involved in this task. Look at your own life and consider what you could change to reduce your carbon footprint, for example. You can network in your work environment and consider how your company, your school, your university can become carbon neutral. You can become involved with the Fridays for Future movement or other groups and become politically active, or you can make a valuable contribution yourself, perhaps in a position of responsibility, by taking the right steps now so that something really changes and we reach the climate goals. You will find your way!

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AFTERWORD This is an awesome book on climate for Human Kind: It is a literary “show and tell”. It truly enables understanding of the link between humans, climate and Earth. I visually devoured this book. It is an amazing picture book for young and old, laypersons and experts. It is a book for the curious, the climate-weary, the fearful, sceptics, know-it-alls - well- simply for everyone: for humanity. Using innovative pictorial translations of complex topics and facts, it explains what climate means to us humans and for the sustainability of the Earth system. Scribbles, cartoons and diagrams are combined in a unique manner with facts and scientific evidence. In a sense this book forms a modern pictorial continuum to the drawings of nature which humans have been doing for over than forty thousand years. Petroglyphs of animals, people, and hunting and life scenes have been discovered all over the world, from Indonesia to Europe. Sight, as a sense, evolved very early on in animal history. The first proto-eyes developed in animals 600 million years ago, around the time of the Cambrian explosion. The first human ancestors are thought to have used UV vision to perceive their environment approximately 90 million years ago. In comparison, the ability to speak developed very late, and the first written language emerged about 5000 years before our era. The recognition of patterns, contrast, light and colours was important for the survival and success of humans. Facial expressions, eye contact, hand gestures, body movements and posture were essential for interactions and for group dynamics and especially so in hunting and dangerous situations. In the current times of Covid and closeted societies, our reliance on visual communication has become extremely clear. Not being able to see people’s facial expressions when

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they speak is somehow distressing and communication is less satisfactory. We are visual animals. In a world where a book on the subject of climate change seemingly is published every week and in the media, it takes courage to re-communicate global warming as an existing threat on paper and particularly in book form. We are flooded with reading material on this subject. Compounding this is the fact that this material is heavy, frightening fare, especially for the stressed Covid-weary person. Who will still read this literature? Is there anything new in it at all, or have the media and the IPCC already said it all? This book is unique. It manages to communicate in an entirely different manner. It sidesteps both the visually rather unattractive and rather technical communication and the media-type communication where visual aids are mostly either HUGE LETTERS, exclamation marks “!” or dramatic photos. We can “see” with this awesome book. The act of “seeing” the messages, which this book stimulates, leads one to hope that this type of communication might reach every type of person. Our most distinctive sense, sight, is activated, and a new type of knowledge transfer is possible. We see that global warming is the greatest challenge facing humanity. It is more than clear that the end of the line for humans on planet Earth is approaching fast, but it is also just as clear that we can still do something about it. Thank you dear Katharina and co-authors for this excellent “show and tell” book. As a climate scientist who works with climate, ecosystems, people and the ocean every day, I “saw” and read every amazing page and relished the excellent translation of this subject, which you herewith provide for us all. Prof. Dr. Karen Wiltshire, Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research

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