The Climate Book

Katherine Hayhoe, a climate scientist, reiterates that greenhouse gases trap radiation in the atmosphere, raising the global temperature. Most people experience “global weirding,” or unexpected weather, like heatwaves. Due to changing weather patterns, atmospheric domes of hot air are stronger, and they deflect cooler air and precipitation, leading to dry, hot weather.

Heatwaves can kill animals and plants, bleach coral reefs, accelerate melting ice, and contribute to wildfires. If changes are not implemented to mitigate climate change, one-third of all life may become extinct by 2050. Humans, too, are vulnerable to extreme heat; it affects humans physically and psychologically and is correlated with increased violence and social instability. It can degrade infrastructure, agriculture, and water supplies. Vulnerable marginalized individuals are the most at-risk of these consequences. Hayhoe suggests people can help by discussing how climate change affects everyone and by sharing ideas to promote change.

Climatologist Zeke Hausfather discusses greenhouse gases other than CO₂ that contribute to climate change, including methane, nitrous oxide, halocarbons, chlorofluorocarbons, hydrochlorofluorocarbons, and industrial chemicals. Methane has a stronger greenhouse effect than CO₂ but is short-lived and breaks down in the atmosphere, while CO₂ does not. Reducing CO₂ emissions now would have more influence on future temperatures, while reducing methane emissions now would have a more immediate effect. This means if methane emission rates remain stable, the methane level in the atmosphere is stable; if CO₂ emissions stabilize, the CO₂ in the atmosphere continues to rise.

Bjørn H. Samset, a climatologist, examines aerosols, or particles that pollute the atmosphere. Aerosols have direct health consequences for those breathing in polluted air, and they impact climate change. Some aerosol particles reflect incoming sunlight or create brighter clouds that reflect incoming sunlight, preventing heat from entering the atmosphere. Dark aerosols in the air or that have landed on ice or snow can cause heat absorption and accelerate ice melting. Samset argues that releasing more aerosols is not a valid solution to climate change because they cause health problems. Many nations are working to eliminate aerosols from the atmosphere, but the results are unpredictable.

Paulo Ceppi, a climatologist, describes how clouds can cool the planet by reflecting sunlight or can heat the planet by functioning as a blanket and trapping radiation, but the cooling effect is more significant. Climate change causes changes in cloud prevalence and types and may alter the balance between the heating and cooling effects of clouds, referred to as “cloud feedback.” So far, computer models have been unable to accurately predict how cloud feedback will impact the climate; however, recent studies show that clouds are appearing higher in the atmosphere, which amplifies their blanket effect. The safest choice, Ceppi writes, is to drastically cut carbon emissions to prevent further harmful changes.

Climate scientist Jennifer Francis addresses the rise in extreme weather events, which are driven, in part, by the warming in the Arctic. The Arctic warms faster than other areas because the decreased snow and ice cover promotes heat absorption rather than reflection. This causes hot, dry summers and higher risks of wildfires in the north, but the impacts for the rest of the planet are influenced by changes to the atmospheric jet stream. Rossby waves occur when the east-west jet stream swings to the north or south. Warmer Arctic air is accompanied by more Rossby waves and more persistent weather conditions, like droughts, and these waves are unpredictable because the atmosphere is chaotic.

Rossby waves exacerbated by climate change were responsible for the destructive freezing temperatures that impacted the southern US in 2021. Rossby waves can also impact summer weather and can split the jet stream, creating areas prone to stagnant weather. Future disruptions to the Arctic jet stream are inevitable; the only way to mitigate escalating extremes is to fight climate change and to prepare for extreme weather events.

Climatologist Friederike Otto claims that climate change is obvious and is a current, not a future, dilemma. Warmer temperatures lead to heavier rainfall during storms, and the rise in sea levels exacerbates storms that develop over water. Models show that such weather would be less extreme if it were not for human-caused climate change. Knowledge of the effects climate change has on individual weather events is important to ensure proper decisions are made in planning for rebuilding after extreme events. However, this science is currently biased in favor of the Global North, meaning less is known about extreme weather in the Global South, where some of the most vulnerable people live.

Thunberg posits that “climate change” is too mild to convey the gravity of global warming and the idea of a warming climate may not seem dire to those living in the Global North. The climate is destabilizing, which is disrupting Earth’s ecosystems. Some glaciers may be near or have already reached a tipping point, meaning it will be impossible to stop them from melting. The speed that glaciers are melting is another issue, as waterflows are currently high but will eventually drop when glacial ice is depleted. Human society was built during the Holocene and may be ill-equipped to handle the Anthropocene.

Kate Marvel, a climate scientist, notes that the water level on Earth has remained stable since water arrived on the planet, and it will remain stable until the sun starts to die. Water changes between solid, liquid, and vapor, and when the Earth warms, it “sweats” more, meaning more water evaporates from the surface, resulting in widespread drought. Hot air retains more water vapor, leading to heavier rains—“A warmer world will suffer from drought but, by the cruel logic of the water cycle, it will flood too” (75). Tree rings show the Earth fluctuates between wet and dry climates, but unnatural patterns are emerging as a result of climate change. For instance, while droughts are normal, simultaneous droughts across the planet are not. Marvel asserts that people must rethink their relationship to the world.

Climatologist Ricarda Winkelmann reflects on her first expedition to Antarctica, where she witnessed melting glaciers and fully realized the damage humans have caused. Ice sheets will keep melting and keep raising sea levels, putting lives at risk. The polar regions are experiencing record high temperatures and melting events, and more icebergs are breaking off ice sheets. Ice sheets sink as they melt, and lower altitudes have warmer temperatures; thus, the ice will reach a tipping point at which the melting becomes unstoppable. Warmer ocean waters melt ice shelves, leading continental ice to accelerate toward the ocean, which could result in a feedback loop. If the temperature continues to rise, ice will continue to melt, and the sea level will rise over hundreds or thousands of years. Decisions today, concludes Winkelmann, will impact future generations.

Stefan Rahmstorf, a climate scientist, cites an article written by Wallace Broker in Nature that refers to greenhouse gas emissions as an experiment with severe consequences. The ocean has absorbed 90% of the additional heat but has risen by an average temperature of 0.9°C, while land temperatures have risen 1.9°C; these numbers are averaged to arrive at 1.2°C of total global warming. When the average reaches 1.5°C, land temperatures will have risen by 2.4°C. The only way to prevent rising above this temperature is to eliminate greenhouse gas emission.

Warmer oceans generate stronger storms, are less efficient at storing CO₂, and may harm marine species. Sea levels rise from meltwater and because water expands as it warms. Since the 1800s, sea levels have risen by 20 centimeters; if all the ice in the polar caps melt, sea levels are expected to rise by 65 meters. One-half to one meter of sea level rise is expected by 2100; however, seas might rise significantly more if emissions continue to rise and if tipping points are reached.

The Atlantic Meridional Overturning Circulation (AMOC) is an ocean current that impacts the climate and delivers heat to the northern hemisphere, making Europe and the north Atlantic warmer than they otherwise would be. The AMOC is changing and cooling the north Atlantic. Evidence shows that the AMOC has collapsed in the past, which disrupted global weather patterns for thousands of years.

Climate scientist Hans-Otto Pörtner writes that CO₂ levels are rising quickly and have reached their highest level in 2 million years. The ocean absorbs CO₂, but as it does, it becomes more acidic and poses a threat to marine life. Ocean acidity has risen by 30% and some consequences will remain long-term even if global emissions are cut. Acidic oceans inhibit calcification, leaving shelled organisms vulnerable, and several species are experiencing behavioral changes and decreased growth and survival. Researchers are uncertain what other consequences ocean acidification and warming will bring or whether plants and animals will be able to adapt quickly enough. Pörtner proposes that humans should work to preserve the ocean by meeting the goals of the Paris Agreement and by officially protecting 30 to 50% of the ocean.

Karen Kvale, a climate scientist, compares microplastics and CO₂, noting that both are caused by human activities and both are long-term pollutants accumulating in the atmosphere and the ocean. Microplastics drift to the bottom of the ocean and into remote areas like the Arctic Ocean. They are so prevalent that Kvale suggests they could be considered a seawater component. Both larger plastics and microplastics negatively impact ocean life: Animals get tangled up and die, or they eat plastic, which causes stress or death and disrupts ecosystems. Ocean sprays transfers microplastics from the water to the atmosphere. Plastic pollution is expected to rise, partly due to claims that it is recyclable, although little plastic is recycled. Plastic waste is often mismanaged due to inefficiencies and lack of regulations in waste management systems.

Hydroclimatologist Peter H. Gleick refers to water as a source of connection and notes that fresh water use has implications for climate change. Since energy systems rely on fossil fuels, fresh water production releases greenhouse gases. Switching to renewable energy sources could make water systems carbon neutral. The water cycle has been disrupted, causing more evaporation and droughts in some regions and heavier rains and flooding in others. Coastal aquifers are being contaminated with saltwater, rivers are disappearing, and reduced mountain snow is limiting access to fresh water. Fresh water access was unstable before climate change, and the rising temperature is exacerbating that instability. Gleick recommends focusing on treating and reusing water, capturing and storing precipitation, desalinating water, and reducing water consumption. Inequalities must be considered, and vulnerable communities should be protected.

Thunberg identifies a pattern: World leaders make vague pledges, fail to comply, then set new vague pledges. It seems as if meaningful change is taking place, but it’s not. The media focuses on distant, rather than local, impacts, leading people to “forget that the climate and ecological crisis is happening everywhere, all the time” (91). The ecological crisis is exacerbated by certain attempts to reduce CO₂ emissions. For instance, biomass, like trees, is burned in place of fossil fuels. Although burning wood releases more CO₂ than burning fossil fuels, the greenhouse gases emitted by burning biomass are not counted in the officially reported CO₂ levels. Trees are cut explicitly to burn to generate electricity because it is lucrative and makes it seem as if climate goals are being met.

World leaders have been creating loopholes and prioritizing economic status over the environment, argues Thunberg. Since the 2021 Climate Change Conference (COP26), many nations are still funding practices like deforestation and oil production—details that the media fail to report.

Climate scientist and author Joëlle Gergis writes that deforestation, agriculture, and industrialization have altered global fire activity. Due to their complexity, wildfires are difficult to predict or monitor. Their potential consequences are not well-understood, but they are known to contaminate air and water quality and to destroy habitats. The higher temperatures and erratic weather patterns caused by climate change are exacerbating wildfires. For instance, 21% of Australia’s temperate forests were lost in a ‘megafire’ in 2019-20. The fire released 715 million tonnes of CO₂ and killed or displaced 3 billion animals. Wildfires contribute to a feedback loop: Rising temperatures increase the prevalence of wildfires, and wildfires contribute to rising temperatures. Limiting global warming will reduce the risk of wildfires and may allow ecosystems to rebalance.

Earth system scientist Carlos A. Nobre, plant ecologist Julia Arieira, and geographer and earth system scientist Nathália Nascimento discuss the Amazon rainforest—the largest rainforest in the world. The Amazon absorbs and stores carbon, influences Earth’s weather patterns, and promotes cooling through evapotranspiration, or the absorbing and releasing of atmospheric water vapor. Rising temperatures, decreased moisture, and industrial and agricultural activities raise the risk of forest fires, and dark aerosols and decreased evapotranspiration amplify dry conditions. Seventeen percent of the Amazon has been deforested and another 17% has been degraded. A feedback loop emerges in that degraded forests are more likely to experience wildfires, and wildfires reinforce climate change.

Large areas of the Amazon may turn into degraded savannahs. If human activity doesn’t change, up to 60% of the Amazon may be lost by 2050, which would have severe climate, environmental, health, and social implications. As the Amazon degrades, it may reach a tipping point where it produces more carbon than it absorbs, which would make limiting global warming to the agreed upon 1.5°C impossible. It would also result in deadly living conditions for people living in and near the Amazon.

Beverly E. Law, a forest scientist, notes that boreal and temperate forests cover almost as much ground as tropical forests, and they harbor diverse species. Boreal forests covering large northern areas provide migration routes and store carbon, but they are largely unprotected, are harvested for wood, and are experiencing increased wildfire activity. Rising temperatures encourage the boreal forest to extend northward, expanding green areas that can absorb carbon; however the expansion is impacting migration routes and has led to caribou becoming endangered.

Temperate forests similarly absorb and store carbon and are facing heavy deforestation. Some forests have become carbon sources rather than sinks, such as forests in British Columbia that have been weakened by pests and wildfires. The area is experiencing faster temperature rises, which benefit the pests and allows them to expand into new territories. Forest emissions are not included in the official reports; if they were, the emissions report for British Columbia would rise by 40%. To efficiently remove and store carbon, forests need to mature.

Adriana De Palma, a computational ecologist, and Andy Purvis, a biodiversity scientist, stress the environmental and health benefits of biodiversity. Biodiversity is highest in mountainous forested areas that have had a stable climate for millions of years, while large areas with similar climates and cold areas have lower biodiversity. Humans have caused three waves of change that have impacted biodiversity. The first occurred when early humans spread across the globe and caused numerous extinctions; the second was during the agricultural revolution around 10,000 years ago; and the third was a result of industrialization. Biodiversity is now threatened by hunting, farming, industrialization, and climate change. Climate change is expected to increasingly degrade global biodiversity, but extinction rates can be slowed if humans work to restore natural environments.

Ecologist Dave Goulson reflects on his life-long appreciation for insects, which inspired him to specialize in bee ecology. Insects are a vital facet of the environment; they are food sources, they eat pests, they benefit the soil, and they pollinate plants. Insect populations have rapidly declined due to environmental degradation, including habitat destruction and the widespread use of pesticides. The changing climate impacts insect species, with some, like mosquitos, benefitting from rising temperatures while others, like bees, are harmed. Insects are an important part of a balanced ecosystem, and if their numbers continue to decline, the results may be catastrophic. To increase insect populations, Goulson suggests society needs to learn to value insects, to incorporate more green spaces, and to transform the food system. Most insect species have not yet gone extinct, and their populations can be restored.

Keith W. Larson, an ecologist, explores how shifts in climate impact migratory and seasonal species. Phenology is the phenomenon that occurs when a species undergoes changes throughout the year, such as deciduous trees that grow in warm months and are dormant through winter or bears that hibernate over winter. Animal ranges and phenology are changing, with some species altering their range, some adjusting the timing of their phenological events, and some dying. Animals appear to be evolving to have smaller bodies, as smaller bodies are easier to cool; however the speed of human-caused climate change may prevent some species from adapting. Disruptions to range or phenology may impact symbiotic relationships, like the relationship between plants and pollinators. Predicting the exact impacts of climate change is impossible because of the complexity of the interacting factors.

Soil carbon scientist Jennifer L. Soong writes that soil holds more than 3,000 gigatonnes of carbon. Humans are dependent on soil for a variety of reasons, including food production and carbon absorption. Plants take in CO₂; when they die and decompose, the carbon is transferred to the soil, and the resulting nutrients feed plants. Some CO₂ is released back into the atmosphere, while some is trapped in the ground. Disruptions to this cycle significantly impact the climate, and as temperatures rise, more CO₂ is released from the soil, exacerbating climate change. Soong suggests that to prevent this, humans need to reduce emissions, protect nature, modify agricultural practices, and plant deep-rooted plants to protect the soil.

Biogeochemist Örjan Gustafsson discusses how the thawing of permafrost and collapsing methane hydrates could hasten the climate crisis. Permafrost is permanently frozen ground, and it stores a significant amount of CO₂. Hydrates are stores of frozen methane that develop beneath the seabed. As temperatures rise, CO₂ and methane are released into the atmosphere, and warming and heavy rains can degrade the environment and disturb deep carbon deposits. Scientists studying underwater permafrost and hydrates have recorded hundreds of sites with methane bubbling to the surface, indicating that the underwater permafrost has been weakened—“This sleeping giant is starting to wake up” (121). To prevent damage, Gustafsson calls for humans to stop extracting fossil fuels and to reduce air pollution, particularly dark-colored aerosols.

Tamsin Edwards, a climate scientist, discusses the impacts of global warming. The average global temperature has risen a little over 1°C, and droughts, floods, fires, and extreme weather are more prevalent. Warming occurs faster over the land and polar regions, and it amplifies the water cycle, leading to droughts and floods. If the temperature rises 1.5°C, extreme heat will be four times more likely; at 2°C it will be six times more likely, and at 4°C, extreme heat will occur regularly. Similar patterns occur with drought and heavy rain events. At 1.5°C, Arctic sea ice will nearly disappear in the summer and reform weaker in the winter, and at higher temperatures, the ice will disappear completely during summer and may not reform in winter.

If humans act to limit global warming to 2°C or less, sea level rise could be limited. If they continue to emit greenhouse gases, the temperature will rise by 10°C by 2300, glaciers will be gone, and seas might rise by seven meters. Even if emissions stop immediately, glaciers will continue to melt. Edwards hopes that, in the future, people can reverse global warming, and she argues that people should take whatever steps they can to slow climate change.