The Impacts of Climate Change: A Comprehensive Study of Physical, Biophysical, Social, and Political Issues

By Trevor Letcher

The Impacts of Climate Change: A Comprehensive Study of Physical, Biophysical, Social and Political Issues presents the very real issues associated with climate change and global warming and how it affects the planet and everyone on it. From a physical perspective, the book covers such topics as population pressures, food issues, rising sea-levels and coastline degradation, and health. It then goes on to present social impacts, such as humanitarian issues, ethics, adaptation, urban issues, local action, and socio-economic issues. Finally, it addresses the political impacts, such as justice issues and politics of climate change in different locations.

By offering this holistic review of the latest impacts of climate change, the book helps researchers to better understand what needs to be done in order to move toward renewable energy, change societal habits, and move toward sustainable development.

• Offers comprehensive coverage of the impacts of climate change from multiple perspectives (physical, social, and political) to develop synergy across disciplines
• Presents the latest research and developments on the understanding of climate change impacts on a variety of scales and disciplines
• Includes case studies and extensive references for further exploration

• Language: English
• Publisher: Elsevier Science
• Release date: May 9, 2021
• ISBN: 9780128223741

Book preview

Section A

Introduction

Chapter 1: Why discuss the impacts of climate change?

Trevor M. Letcher    Laurel House, Stratton on the Fosse, Bath, United Kingdom

Abstract

This book is about the impact of climate change on the planet's ecosystem and human beings. In this book, only a few topics have been chosen to highlight the impacts of climate change on the physical and biophysical aspects of the planet. They include melting glaciers and ice sheets, natural disasters, food issues, biodiversity, microorganisms, and marine ecosystems as they all have a direct effect on the human population. The indicators of climate change on the weather patterns, sea levels, wind systems, ocean currents, animal, bird and insect ecology, sea life, corals, marine and intertidal ecology, plant ecology, and plant pathogens have been dealt with in detail and at great length in Climate Change 2nd edition. The major part of this new book relates to the social and political issues as impacted by climate change. The social impacts of climate change stem from: food production problems; population movements and expansion; economics related to ecological changes; societal adaption, attitudes and pressures on urban life. The chapters in this book gives insights into these changes that are taking place in our society. There is no precedent for coping with these issues. The section on political aspects focuses on security, governance, justice, the law and ethics as related to climate change; all of which involve issues that are new and need new solutions and preferably solutions that are universal and can be adopted worldwide. Again, we must look at international cooperation for finding solutions; this is bought home to us in the final chapter on climate refugees. This is a very new problem and can only be solved with collaboration from all governments. The COVID-19 pandemic has been a wake-up call to the world for more international cooperation to solve global issues including the impacts of climate change. Focusing on the issues discussed in this book, we should be better prepared to cope with future impacts of our changing climate. That is the raison d’etre for this volume.

Keywords

Global warming; Climate change; Feedback mechanisms; The greenhouse effect; COVID-19; Society

Outline

1.Introduction

2.The greenhouse effect

3.Global warming

4.Feedback mechanisms to further increase the heating of the planet

5.Other possible causes of climate change

6.Urgent action is required

7.Our present situation

8.Global warming, climate change, and the new pandemic—COVID-19

9.How global warming affects society

10.Conclusions

References

1: Introduction

The world is entering an unprecedented time of global warming which is affecting our climate on which we depend for our very existence. Global warming is causing changes in rain and snow patterns; rising sea levels; increased severity and frequency of droughts, wildfires, storms, tornadoes, and hurricanes; high temperatures and heatwaves and changes to our social fabric and political structures. Global warming is the most important calamitous change our civilization has ever had to face. In another publication Climate Change 2nd edition (Letcher, 2015), the physical and biological effects of rising global temperatures were discussed but little was made of the effects on society and on human life. This book puts that to right. These impacts which are now blatantly obvious become more and more important with each passing year and are poised to change our lives and those of our children and their children forever. We must plan our future with these changes in mind. This is the raison d’etre for this volume.

Before reading the chapters in this book, it is important that we look at the origins and the physics and chemistry of global warming and let the science tell us just how serious a position our ecosystem and our society is in. The temperature and climate of our planet has been more or less constant for the best part of a million years and it is under this regime of climate that our ecosystem and indeed human life evolved. Any significant deviation from this equilibrium will have a devastating effect on both the ecosystem and on human life. We are fast reaching this stage.

The fundamental mechanism leading to the warming of our planet is the greenhouse effect. This initial warming effect is followed by certain feedback mechanisms (e.g., evaporation of water from the oceans, the reduction in albedo effect on polar ice sheets) which exacerbates the situation leading to further global warming and perhaps, in the not too distant future, a run-a-way global warming catastrophe. Understanding the causes of global warming and the present situation give reader a background to appreciating the different impacts climate change is having on our society. This must indeed educate and galvanize the reader to do something about reducing the onset of a catastrophic collapse of our society and the way we live.

2: The greenhouse effect

Much of what follows in this section has been discussed in Chapter 1 of Managing Global Warming (Letcher, 2019). It is pertinent to include it here at the beginning of The Impacts of Climate Change. The concept of the greenhouse effect goes back to the 1820s, when Joseph Fourier suggested that some component of the earth's atmosphere was responsible for the temperature at the surface of the earth. He was researching the origins of ancient glaciers and the ice sheets that once covered much of Europe (Fourier, 1824). Decades later, Tyndall followed up the Fourier's suggestion, and used an apparatus designed by Macedonio Melloni to show that CO2 was able to absorb a much greater amount of heat than other gases. This fitted in with Fourier's concept and pointed to CO2 as the component in the atmosphere that Fourier was looking for. The Melloni apparatus was called a thermomultiplier, and was reported in 1831 (Nobili and Melloni, 1831; Sella, 2018). Tyndall's results were published in references (Tyndall, 1861, 1863). As a result, Tyndall can be named as the discoverer of the CO2 greenhouse gas effect.

Linking CO2 in the atmosphere to the burning of fossil fuels was to be the last link in the chain in understanding the reasons for the ice ages and also our own climate change. In the 1890s, Svante Arrhenius, an electrochemist, calculated that by reducing the amount of CO2 in the atmosphere by half, the temperature of Europe would be lowered by about 4–5°C. This would bring it in line with ice age temperatures. This idea would only answer the question of why the ice age formed and then retreated, if there were large changes in atmospheric composition and in particular, changes in CO2 concentration. At much the same time, also in Sweden, a geologist, Arvid Högbom, had estimated that CO2 from volcanic eruptions, together with the ocean uptake of CO2, could explain how the CO2 concentrations in the atmosphere could change and hence provide some explanation for the ice ages. Along the way Högbom stumbled on a strange and new idea that the CO2 emitted from industrial coal burning factories might influence the atmospheric CO2 concentration. He did indeed find that human activities were contributing CO2 to the atmosphere at a rate comparable to the natural geochemical processes. The increase was small compared to what was already in the atmosphere, but if continued, it would influence the climate. Arrhenius took up this concept, and his calculations are published (Arrhenius, 1896). Arrhenius concluded that the emissions from human industry might someday bring on global warming. Hence, Arrhenius's name is forever linked to the greenhouse theory of global warming. However, thanks must also go to those who paved the way—Fourier, Melloni, Tyndall, Högbom, and probably many others.

Arrhenius's calculations were at first dismissed as unimportant or at worst faulty. A similar fate was met by G.S Callendar who, in 1938, made the point that CO2 levels were indeed climbing (https://www.rmets.org/sites/default/files/qjcallender38.pdf). It was only in the 1960s, after C D Keeling measured the CO2 concentration in the atmosphere and showed that it was rising rapidly, that scientists woke up to the fact that global warming was real and that anthropogenic activity was to blame.

Water vapor is an even more effective greenhouse gas than CO2. Furthermore, its concentration in the atmosphere is very much higher than that of CO2 (of the order of a hundred times higher), and H2O contributes over 60% of the global warming effect. The amount of water vapor in the atmosphere is controlled by the temperature. An increase in the CO2 concentration in the atmosphere results in a relatively small increase of the global temperature but that change is enough to increase the amount of water vapor in the air, through evaporation from the oceans. It is this feedback mechanism that has the greatest influence on global temperature. In a sense, paradoxically, the concentration of CO2 acts as a regulator for the amount of water vapor in the atmosphere and is thus the determining factor in the equilibrium temperature of the earth. Without CO2 in the atmosphere, the temperature of the earth would be very much cooler than it is today; in fact, 33°C cooler.

The amount of solar energy shining on the earth (with wavelengths ranging from 0.3 to 5 μm) is vast. It heats our atmosphere and everything on the Earth and provides the energy for our climate and ecosystem. At night, much of this heat energy is radiated back into space but at different wavelengths, which are in the infrared range from 4 to 50 μm (earthguide.ucsd.edu/virtualmuseum/climatechange1/02_3.shtml). The frequencies of the heat radiating from a body is dependent of the temperature of the body (Planck's Law of blackbody radiation). This energy, leaving the Earth, heats the greenhouse gas molecules (such as H2O, CO2, CH4, etc.) in the atmosphere. The explanation is as follows: using CO2 and H2O as examples, this heating process takes place because the radiated IR frequency is in sync (resonates) with the natural frequency of the carbon-oxygen bond of CO2 (4.26 μm being the asymmetric stretching vibration mode and 14.99 μm being the bending vibration mode) and the oxygen-hydrogen bond of H2O. The increased vibration of the bonds effectively heats the CO2 and H2O molecules. These heated molecules then pass the heat to the other molecules in the atmosphere (N2, O2) and this keeps the earth at an equitable temperature. The vibrating frequencies of the O glyph_sbnd O bond in oxygen and the N glyph_sbnd N bond in nitrogen molecules are very different from the radiation frequencies and so are unaffected by the radiation leaving the Earth at night.

3: Global warming

The scientific evidence that global warming is largely because of the rising CO2 levels in the atmosphere is overwhelming and, furthermore, that the rising CO2 concentration is because of human activities. Every scientific society and every research organization working in the field of climate change accepts this view. The atmospheric CO2 concentration has increased from 280 ppm (280 ppm or 280 molecules per million molecules) (https://link.springer.com/article/10.1007/BF02423528) before the industrial revolution to 417 ppm (observed at Mauna Loa Observatory on May 2020) (https://www.co2.earth/daily-co2), and it is this increase of almost 50% that has triggered the present increase in global temperature.

The total amount of CO2 in the atmosphere and its concentration value are the most dependable measurements we have for the progress of global warming. In 1960, the rate of increase of CO2 (as measured at Mauna Loa, in Hawaii) was less than 1 ppm per year. It is now 2.4 ppm per year (https://link.springer.com/article/10.1007/BF02423528). It is this rate of change that is the best indicator of any progress we are making in reducing global warming. At the moment there is no sign that this is happening, in fact the reverse is true. Even if we stopped burning fossil fuel, the CO2 levels will take a long time to decrease as the lifetime of CO2 in the upper atmosphere is of the order of hundreds of years.

The most compelling evidence that the increase in CO2 is the most likely cause of global warming can be seen in the related graphs of CO2 concentration in the atmosphere and the global average temperature as functions of time over the past many decades (see Figs. 1 and 2). The CO2 increase is mirrored by an increase in the relative increase in average global temperatures over the past 60 years.

Fig. 1

Fig. 1 The increase of CO 2 concentration over the past 60 years. https://en.wikipedia.org/wiki/Keeling_Curve Data from Dr. Pieter Tans, NOAA/ESRL and Dr. Ralph Keeling, Scripps Institution of Oceanography.

Fig. 2

Fig. 2 The relative increase in the world's average surface air temperature from 1880 to 2009. Original data produced by ASA's Goddard Institute for Space Studies (http://data.giss.nasa.gov/gistemp/graphs/).

A question which needs answering is this: we know that the CO2 level in the atmosphere is rising steadily: but is the CO2 increase because of human activity? The evidence that it is indeed because of human activity is based on the relative ratios of carbon isotopes. The relative amount of ¹³C in the atmosphere has been declining and that is because the ratio of ¹³C in fossil fuel-derived CO2 is significantly lower that the CO2 produced from present-day decaying plants (http://www.realclimate.org/index.php/archives/2004/12/how-do-we-know-that-recent-cosub2sub-increases-are-due-to-human-activities-updated/).

From the properties of each of the greenhouse gases (such as the wavelengths of energy), scientists can calculate how much of each gas contributes to global warming. The results show that CO2 is responsible for about 20% of the earth's greenhouse effect, water vapor between 60% and 80% (https://www.acs.org/content/acs/en/climatescience/.../its-water-vapor-not-the-co2.html or https://www.nasa.gov/topics/earth/features/vapor_warming.html). It is, however, CO2 that is the driver and trigger of global warming. The rest is caused by minor greenhouse gases such as methane and chlorinated hydrocarbons. The relative concentrations of the major greenhouse gases emitted by human activity in the USA are: CO2 81%; CH4 10%, and N2O 7% (https://www.epa.gov/ghgemissions/overview-greenhouse-gases).

It is perhaps of interest to note that it is not possible to obtain absolute proof that it is CO2 which is largely responsible for global warming because we cannot do the definitive experiment of suddenly stopping the use of fossil fuels. And even if we could do this experiment it would take decades to obtain a definite conclusion because of the long-life CO2 has in the atmosphere (https://www.epa.gov/ghgemissions/global-greenhouse-gas-emissions-dat).

Most of the anthropogenic CO2 entering the atmosphere comes from fossil fuels. The relative fraction of energy produced by fossil fuels has remained at over 86% over the past decade as is illustrated by worldwide primary energy consumption listed in Table 1. However, the quantity of fossil fuel extracted from the earth has increased significantly over the past 11 years, as seen in Table 2. This is reflected in the steadily increasing amount of CO2 entering the atmosphere. However, between 2015 and 2016, world oil production increased by only 0.4%, world coal production fell by 6.2%, and natural gas increased by only 0.3%. This is the first sign that fossil fuel usage is slowing down.

Table 1

Table 2

The Global Carbon Project (GCP) (http://www.globalcarbonproject.org/) has reported that emissions in 2015 from burning fossil fuels and also from industry (especially cement production) account for 91% CO2 caused by human activity with 9% from land use changes. In 2015, the GCP has reported that 9.9 × 10⁹ t of carbon in the form of CO2 from burning fossil fuels entered the atmosphere. Nevertheless, the GCP felt that there were signs that the emission of CO2 from human activity was indeed showing signs of peaking.

4: Feedback mechanisms to further increase the heating of the planet

There are many CO2 feedback mechanisms at play and five of them are summarized below.

The water vapor feedback mechanism has been discussed above and it is this feedback mechanism that has the greatest influence on global temperature.

The melting of ice contributes to another feedback mechanism. When ice melts, land or open water takes its place. Both land and open water are on average less reflective than ice and thus absorb more solar radiation. This causes more warming, which in turn causes more melting, and this cycle continues.

The oceans are a storehouse for CO2 but the amount it stores is limited by the solubility of CO2 in seawater. This solubility is dependent on the temperature. Global warming results in a warmer sea and a lowering of the CO2 solubility, resulting in some CO2, leaving the oceans and entering the atmosphere, which in turn increases global warming and so on…

Another feedback mechanism is at play in the peat bogs and permafrost regions of the world, such as in Siberia and in Greenland. Rising global temperatures are melting the permafrost and will in time release vast quantities of methane gas (CH4). This gas is over 25 times more effective than CO2 as a greenhouse gas.

Yet another feedback mechanism involves methane clathrates, a form of water ice that contains methane within its crystalline structure. Extremely large deposits of it have been found under the sediments on ocean floors. An increase in temperature breaks the crystal structure releasing the caged methane. Rising sea temperatures could cause a sudden release of vast amounts of methane from such clathrates resulting in a runaway global warming events.

5: Other possible causes of climate change

In spite of the evidence presented above, there has been much debate as to whether our present global warming and climate change could in fact be because of effects other than atmospheric gases. These include: the variation in the sun's energy; volcanic activity; changes in the earth's orbital characteristics, including the Malankovitch cycles; cosmic ray effects; and atmospheric aerosols. These have all been discussed in chapters in Climate Change (Letcher, 2015) by world experts and the consensus of opinion is that none of them could not possibly be responsible for our present climate change (Stenchikov, 2016). The conclusion of scientists around the world is summed up by Macott et al. who wrote The earth's climate is complex and responds to multiple forcings, including CO2 and solar insolation. Both of those have changed very slowly over the past 11,000 years. But in the last 100 years, the increase in CO2 through increased emissions from human activities has been significant. It is the only variable that can best explain the rapid increase in global temperatures (Shakun et al., 2012).

Overall, human sources of CO2 are much smaller than the natural emissions from animals, plants, decaying animals, vegetation, and volcanoes (https://earthobservatory.nasa.gov/Features/CarbonCycle/page5.php). However, human activity has upset the balance in a cycle that has existed for thousands of years. The amount of carbon on the earth and in the atmosphere is fixed but it is in a dynamic and equilibrium cycle, moving between living and nonliving things, and changing into different carbon compounds such as carbon dioxide in the air and in the oceans, solid carbonate rock, and the living cells of plants and animals. In the first step of the cycle, plants take up CO2 from the air through the process of photosynthesis, and release oxygen. The CO2 is then converted into living cells. In the next step, the animals eat the plants, and the carbon in the plant cells are used to build animal tissue and cells. Animals also breathe in oxygen and exhale carbon dioxide which in turn enter the atmosphere and the cycle continues. Dead plants and dead animals decompose and carbon is either released as CH4 and CO2 or stored in the soil. Superimposed on this cycle is the exchange of CO2 between the atmosphere and the oceans. These processes were in near perfect equilibrium before the industrial revolution (https://earthobservatory.nasa.gov/Features/CarbonCycle/page5.php) (Denman et al., 2007).

The evidence that global warming is altering our climate is very well documented, and almost no day goes by without more evidence for climate change. The indicators include: more extreme weather events in the future; melting of Arctic sea ice; Antarctic Sea changes; land ice behavior (including glaciers and ice sheets); weather pattern changes; bird ecology changes (including migration); mammal and insect ecology changes and biodiversity loss; sea life and coral reef changes; marine diversity and intertidal indicators; plant ecology and plant pathogen changes; rising sea levels; and ocean acidification (Letcher, 2016).

6: Urgent action is required

There is a growing threat of environmental collapse in the future, as a result of changes in our present climate. We are beginning to see this with extreme weather events such as flooding, droughts and water crises, high winds, runaway fires, wash-aways, and mud flows from land denuded of its natural rain soaking properties, high seas in coastal areas, together with rising sea levels, to mention a few. One consequence of climate change is the migration of insects and animals to more hospitable climates. A more frightening involuntary mass migration has already begun: of humans from lands unable to support the growing of crops and from areas where rising sea levels are beginning to threaten livelihood. It is not only natural disasters that are a cause for concern but also man-made disasters which result indirectly from global warming that are a cause for concern. These include: the reduced ability of land to soak up rain water as a result of land clearances and urban development resulting in flooding; chemical pollution in the form of pesticides, endocrine disruptors and hormonally active agents used on farms to increase yields; nuclear disasters through extreme weather; land-use decisions for agriculture; oil fires, coal mine fires and even tyre fires which add their own contribution to rising CO2 levels (https://www.ecotricity.co.uk/our-green-energy/energy-independence/the-end-of-fossil-fuels).

Most world governments have accepted the assessment of the United Nations Framework Convention on Climate Change (UNFCCC) that a 2°C rise in mean global temperature above the preindustrial level must be the maximum limit. In order to meet this objective, studies generally indicate the need for global greenhouse gas emissions to peak before 2020 with a substantial reduction in emissions thereafter.

We need to reduce the amount of CO2 entering the atmosphere and if possible, we should find ways of removing some of the CO2 presently in the atmosphere. Present day CO2 levels in the atmosphere exceed the natural equilibrium of dissolved CO2 in the oceans and with the CO2 uptake by biota on land. Unfortunately, this rising nonequilibrium amount of CO2 remains in the air for a very long time. The reason is that CO2, unlike other greenhouse gases such as CH4, is very un-reactive. It does not naturally react with most chemicals and in thermodynamic terms, it has a very high Gibbs Energy of Formation. In order to bring about a reaction of CO2 with another chemical, a significant amount of energy must be given to the system (e.g., heat energy). This is also the reason why it is so difficult to get rid of waste CO2 from chemical reactions (e.g., cement manufacture, or even from burning fossil fuels) and why it is rarely used as a chemical feedstock in industry.

There are still large reserves of coal oil and gas in the earth. These convenient sources of energy are not only easy to use for heating and for producing energy, but exist in a stored form which allows them to be used at any time in the future. It has been estimated (https://www.ecotricity.co.uk/our-green-energy/energy-independence/the-end-of-fossil-fuels) that globally, we currently consume the equivalent of over 11 billion tonnes of oil from fossil fuels every year. Crude oil reserves are vanishing at a rate of more than 4 billion tonnes a year—so if we carry on as we are, our known oil deposits could run out in just over 53 years. If we increase gas production to fill the energy gap left by oil, our known gas reserves only give us just 52 years left. Although it's often claimed that we have enough coal to last hundreds of years, this doesn’t take into account the need for increased production if we run out of oil and gas. If we step up production to make up for depleted oil and gas reserves, our known coal deposits could be gone in 150 years. Another set of estimates have been given by British Petroleum (BP) in 2018. The figures were a little less optimistic. Their estimation of the time left for fossil fuel as a result of present-day usage was predicted to be: oil will end in 30 years, gas in 40 years and coal in 70 years (https://mahb.stanford.edu/library-item/fossil-fuels-run/). Our future mindset must however not be seduced by the convenient properties of fossil fuel, but for the sake of the planet, the reserves must stay forever below ground and nonfossil fuel sources of energy should be embraced.

What is also required is the need for the world to replace growth in the financial sector with sustainability for the future of the society and the world's ecosystem. We cannot carry on as we are and perhaps the present COVID-19 pandemic has given us time to rethink our lives and follow the advice of Riccardo Mastini in reference (http://unevenearth.org/2020/02/a-post-growth-green-new-deal/). To summarize, from a postgrowth perspective a Green New Deal must pursue three distinct but interrelated goals: decreasing energy and material use, decommodifying the basic necessities of life, and democratizing economic production. Any Green New Deal proposal that does not address head-on the drivers of economic growth is doomed to fall short of the challenge of steering away from the worst scenarios of ecological breakdown. This is also the sentiment of Jason Hickel who wrote in reference (Hickel, 2020), The world has finally awoken to the reality of climate breakdown and ecological collapse. Now we must face up to its primary cause. Capitalism demands perpetual expansion, which is devastating the living world. There is only one solution that will lead to meaningful and immediate change: and that is degrowth.

7: Our present situation

This past year, 2019, was again one of the hottest on record (https://climate.nasa.gov/news/2945/nasa-noaa-analyses-reveal-2019-second-warmest-year-on-record/). According to independent analyses by NASA and the National Oceanic and Atmospheric Administration (NOAA), Earth's average global surface temperature in 2019 was the second warmest since modern record-keeping began in 1880. Globally, average temperature in 2019 was second only to that of 2016 and continued the planet's long-term warming trend: the past 5 years have been the warmest of the last 140 years. This past year was 0.98°C warmer than the 1951–80 mean, according to scientists at NASA's Goddard Institute for Space Studies (GISS) in New York (https://climate.nasa.gov/news/2945/nasa-noaa-analyses-reveal-2019-second-warmest-year-on-record/). It shows that we are not doing enough to reduce the amount of CO2 in the atmosphere. The only way to reduce global warming is to reduce the amount of CO2 we are pumping into the air, and if possible, removing CO2 from the atmosphere.

At present, less than 20% of all energy sources are either renewable (wind, solar, hydropower, biomass tide, and geothermal) or nuclear. Replacing fossil fuel to reduce significantly our CO2 emissions is going to be a mammoth task.

The world is not replacing fossil fuel with renewable forms of energy fast enough. This was emphasized in 2019 by Spencer Dale, Chief Economist at BP who stated: There is a growing mismatch between societal demands for action on climate change and the actual pace of progress, with energy demand and carbon emissions growing at their fastest rate for years. The world is on an unsustainable path (https://www.bp.com/en/global/corporate/news-and-insights/press-releases/bp-statistical-review-of-world-energy-2019.html).

It is possible for solar energy to power the world. In less than 80 min, the solar equivalent energy of the total world energy use for a year, strikes the Earth; this implies that in theory the sun could power the world 7000 times.

It has been estimated, that in 2015, human activities contributed 36.8 × 10⁹ t of CO2 through burning coal and other fossil fuels, cement production, deforestation, and other landscape changes (https://www.carbonbrief.org/analysis-global-fossil-fuel-emissions-up-zero-point-six-per-cent-in-2019-due-to-china#:~:text=Emissions%20from%20fossil%20fuel%20and,Global%20Carbon%20Project%20(GCP)). It has also been estimated that since the Industrial Revolution, over 2000 × 10⁹ t of CO2 have been added to the atmosphere. Human activities emit 60 or more times the amount of carbon dioxide released by volcanoes each year (https://www.climate.gov/news-features/climate-qa/which-emits-more-carbon-dioxide-volcanoes-or-human-activities).

The population of the world is increasing and so is the need for more energy with a greater demand for more electricity. The world population (it is now 7.6 × 10⁹ according to the latest 2018 United Nation estimate) is expected to reach 9 × 10⁹ in 2050. It is increasing at a rate of 1.09% per year at the moment (2018) down from 1.14% yr− 1 in 2016 and down from the peak in 1963 of 2.2% yr− 1. The expected rate of growth in energy demand over the next decade is greater than the growth rate of the population; this is largely because of the increase demand for electricity in developing countries. Electricity generation is expected to increase from 25 × 10¹² kWh in 2017 to 31.2 × 10¹² kWh in 2030 an increase of almost 2% per year (https://www.statista.com/statistics/238610/projected-world-electricity-generation-by-energy-source/).

At the moment, coal is still the largest producer of electricity worldwide, and is not expected to be overtaken by renewables until 2040. The relative breakdown of electricity producers and future predictions is given in Table 3. It illustrates the energy dilemma of our time—the positive and encouraging increase in the deployment of renewable forms of energy is masked by the increasing overall energy needs of the world and that increase is still being met by further increases in fossil fuel usage. The present and future world electricity generation is dominated by the burning of fossil fuels (over 60%) and the prediction for 2040 is not much better (58%). It is no doubt driven by a number of forces including: the relative economics of fossil fuels versus renewable energy; the massive inertia linked to status quo situations; and the fear of things new as opposed to well-tried technologies.

Table 3

Electricity production is not the only producer of CO2 in our atmosphere. The various sectors responsible for CO2 generated as a result of human activity is given in Table 4.

Table 4

If there is the necessary political will to do so, we can replace the fossil fuel-derived electricity with renewable forms of energy, or nuclear energy or hydropower. However, we do have a problem with replacing transport fuel. We could 1 day have electric cars replace petrol vehicles and possibly even diesel vehicles, but replacing fossil fuel for air travel and sea travel is difficult if not impossible. Furthermore, some industrial processes such as cement manufacture, involving the heating of CaCO3 resulting in the waste product, CO2, are also problematic. Attempts at replacing petrol in transport with renewable fuel-derived from biomass (sugar cane as done in Brazil or corn as done in the US for petrol, and palm oil in Malaysia for biodiesel) has had some success but the overall contribution has been relatively small (https://www.iea.org/etp/tracking2017/transportbiofuels/). In 2016, the biofuels contributed 4% to the world's transport fuels. The US, Brazil, and Malaysia are the world leaders in biofuels.

All of this does indicate that the world is not on top of solving the global warming problem, in spite of the steady increase in the deployment of renewable forms of energy. The change-over from fossil fuel to renewables is just too slow. It is predicted that renewables will increase their share of electricity production from 21.9% in 2012 to 29.2% in 2040 (less than 0.3% per year) (see Table 1). We will have to work very much harder to replace fossil fuel as the main driving force of our energy industry.

One slight glimmer on the horizon is the fact that natural gas, methane, (including shale gas) is better for the planet than burning coal and in many countries, coal is being replace by natural gas. The reason why natural gas is better than coal is that the amount of CO2 produced from burning CH4 per unit of energy (50 g MJ− 1) is less than it is for coal (92 g MJ− 1) and moreover coal burning produces particulates. Of course, the burning of CH4 still produces CO2:

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8: Global warming, climate change, and the new pandemic—COVID-19

The coronavirus pandemic has been linked to climate change issues. There seems to be little doubt that there is a link between population density, human encroachment on natural areas, and zoonotic disease transmission (https://www.eco-business.com/opinion/covid-19-is-a-product-of-our-unhealthy-relationship-with-animals-and-the-environment/). Climate change through drought, flooding, rising sea levels, unpredictable weather conditions is slowly reducing the arable land in many parts of the world forcing people to move into areas close to wildlife populations that humans had not previously been in close contact with. The disruption of pristine forests driven by logging, mining, the need to find new places to live, the spread of urban development, and population growth is bringing people into closer contact with animal species. In the case of COVID-19, the contact was most likely with bats. As Jane Goodall says, COVID-19 is a product of our unhealthy relationship with animals and the environment and that our exploitation of animals and the environment has contributed to pandemics, including the COVID-19 crisis. Wildlife trafficking, factory farming, and the destruction of habitats are drivers of zoonotic diseases (https://www.eco-business.com/opinion/covid-19-is-a-product-of-our-unhealthy-relationship-with-animals-and-the-environment/). With global warming on the increase, we can expect that climate change will further impact on the spread of infectious diseases through animals as it has in the past with rabies, the plague, Ebola, SARS, MERS, and ZIKA to mention but a few zoonotic diseases.

9: How global warming affects society

Global warming affects societies in many ways. Here below are a few examples:

•Reduces the area available for farming and for human occupation through droughts, floods, and climate change resulting in food shortages.

•Sea level rises result in a loss of housing and farmland which in turn involves human migration, and expensive new housing/buildings.

•Risk of life increases and insurance premiums rise—all insurers suffer.

•Need rapid development of renewable energy to replace fossil fuel.

•Pressure on industry to improve efficiencies, leading to more expensive products.

•Health suffers in many ways. For example, malaria becomes more widespread as a small rise in temperature results in a large vectoral capacity of mosquitoes (development of anopheles is shorter, bites by females increases as gonadotrophic cycle is shortened, incubation period of plasmodium decreases).

•Heat waves kill. It has been estimated that the heatwave in Europe, in 2003, with temperatures of over 45°C, killed 70,000 people. In France, the number of heatwaves has doubled over the past 40 years and is expected to double again by 2050.

•Economics—everything costs more—electric car, electricity, imported food, insurance, need more air conditioning.

•Wild fires—loss of homes, loss of habitat for animals and wild animals.

•Rise in extreme weather patterns (flooding, gales, droughts, too hot, too cold…) reduce time for working.

•Flooding low lying areas of the world causes a loss of infrastructure and housing.

•Increased tropical typhoons and hurricanes leading to loss of life, housing and occupations.

•Droughts—causes of starvation, food shortages, loss of occupation, start of wars—catalyst for unrest in Syria, civil war and human migration, refugees, droughts are reputed to be the most expensive weather-related disasters;

•Mental anguish as a result.

10: Conclusions

We believe that we do understand the underpinnings of global warming and that greenhouse gases and CO2 in particular are the root causes. We know that renewable forms of energy and possibly nuclear energy MUST replace fossil fuel where possible and that this must be done soon. There are limits to what can be replaced as we unfortunately depend on fossil fuels for transport both now and in the foreseeable future. Other areas such as electricity production using fossil fuel can and should be phased out.

Much depends on governments around the world having the will and energy to drive a nonfossil fuel policy. It should be a basic moral decision for the sake of future generations. Governments should not be driven by short-range decisions that benefit the few (including parliamentarians and also shareholders in fossil fueled industries). They should be bold and brave enough to create a legacy for our children and our children's children.

This book is about the impact of climate change on the planet's ecosystem and human beings. The indicators of climate change on the weather patterns, sea levels, wind systems, ocean currents, animal, bird and insect ecology, sea life, corals, marine and intertidal ecology, plant ecology and plant pathogens have been dealt with in detail and at great length in Climate Change 2nd edition. The major part of the book relates to the social and political issues as impacted by climate change. The social impacts of climate change stem from: food production problems; population movements and expansion; economics related to ecological changes; societal adaption, attitudes and pressures on urban life. There is no precedent for coping with these issues. We must however note the changes and make plans with new ways to deal with them. This is a global problem and it is hoped that countries and governments will come together to find solutions to new ways of life as they have for the COVID-19 pandemic. The section on political aspects focuses on security, governance, justice, the law and ethics as related to climate change; all of which involve issues that are new and need new solutions and preferably solutions that are universal and can be adopted worldwide. Again, we must look at international cooperation for finding solutions; this is bought home to us in the final chapter on climate refugees. This is a very new problem and can only be solved with collaboration from all governments.

References

Arrhenius S. On the influence of carbonic acid in the air upon the temperature of the ground. Philiso. Mag. J. Sci. 1896;41:237–276.

Denman K.L., Brasseur G., Chidthaisong A., Ciais P., Cox P.M., Dickinson R.E., Hauglustaine D., Heinze C., Holland E., Jacob D., Lohmann U., Ramachandran S., da Silva Dias P.L., Wofsy S.C., Zhang X. Couplings between changes in the climate system and biogeochemistry. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press; 2007.

Fourier J. Remarques Générales sur les Températures Du Globe Terrestre et des Espaces Planétaires. Ann. Chim. Phys. 1824;27:136–167.

Hickel J. Less is More: How Degrowth Will Save the World. Milton Keynes, UK: William Heinemann; 2020. https://www.penguin.co.uk/books/1119823/less-is-more/9781785152498.html.

Letcher T.M., ed. Climate Change: Observed Impacts on Planet Earth. second ed. New York: Elsevier; 2015:978-0-444-63524-2.

Letcher T.M.… , eds. Climate Change: Observed Impacts on Planet Earth. second ed. Elsevier; 2016:21–Oxford Chapters 2–21.

Letcher T.M. Managing Global Warming: An Interface of Technical and Human Issues. Cambridge, MA: Elsevier; 2019 ISBN: 978-0-12-814104-5.

Nobili L., Melloni M. Le Thermo-multiplicateur. Ann. Chim. (Phys.). 1831;48:198–199.

Sella A. Melloni's thermomultiplier. Chem. World. 2018;15:70.

Shakun J.D., Clark P.U., He F., Marcott S.A., Mix A.C., Liu Z., Otto-Bliesner B., Schmittner A., Bard E. Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation. Nature. 2012;484:49–54.

Stenchikov G. The role of volcanic activity in climate and global change. In: Letcher T.M., ed. Climate Change, Observed Impacts on Planet Earth. second ed. Oxford: Elsevier; 2016:419–448.

Tyndall J. On the absorption and radiation of heat by gases and vapours…. Philos. Mag. Ser. 4. 1861;22: 169–94, 273–85.

Tyndall J. On radiation through the earth's atmosphere. Philos. Mag. Ser. 4. 1863;25:200–206.

Further reading

Vallero D.A., Letcher T.M., eds. Unraveling Environmental Disasters. Oxford: Elsevier; 2013 (Chapters 8, 12, 13, 14).

Chapter 2: Impacts of climate change on economies, ecosystems, energy, environments, and human equity: A systems perspective

Daniel P. Loucks    Cornell University, Ithaca, NY, United States

Abstract

The substantial and continuing increase in greenhouse gas emissions from the use of primarily fossil fuels to meet increasing energy demands have made the Earth’s climate increasingly hotter. It is also wetter where it is wetter and drier where it is drier. The weather is more extreme. The adverse impacts and consequences of this extreme weather on our economies, ecosystems, environment, and even energy sectors are increasingly evident. The magnitude of each impact differs in particular regions—but together, the temporal range and spatial extent of these extremes makes climate change one of the most urgent and long-term issues facing the world’s populations today. Global warming is adversely impacting the health and economic and social well-being of people, communities, and nations, worldwide. The most vulnerable—those with fewest resources and options available to respond—are being the most impacted.

This chapter attempts to identify the interdependencies among the major economic, ecological, environmental, and energy sector impacts, and associated social equity issues, resulting from today’s changing climate. These impacts include more frequent and intense storms, wildfires, and heat waves; air, soil, and water pollution; crop failures; shifts in ecosystem habitats; freshwater shortages; worsening smog; health risks to humans, animals and plants; melting ice sheets, glaciers, and permafrost; rising sea levels and damage to coastal communities and infrastructure in virtually every sea-bordering country in the world and possibly permanently flooding entire island nations. These are only a few of the consequences of global warming that are among others reviewed in this chapter.

As the direct and damaging impacts of climate change on food supplies, human health, commerce, industries, and ecosystem services become more severe, and as conflicts over increasingly scarce resources worsen, political and social tensions increase. Regions become less livable. People leave. These migrations significantly increase risks of conflicts. The economic, social, and political costs resulting from our increasing emissions of greenhouse gases into the atmosphere clearly outweigh those costs of decreasing them.

Keywords

Climate change; Global warming; Economic impacts; Environment; Energy; Equity; Ecosystems

Outline

1.Introduction

2.Climate change

3.Ecosystem impacts

3.1Agricultural ecosystems

3.2Urban ecosystems

3.3Forest ecosystems

3.4Aquatic ecosystems

3.5Grassland ecosystems

3.6Desert ecosystems

4.Economic impacts

4.1Agriculture

4.2Business and industry

4.3Infrastructure

4.4Human health and productivity

4.5Tourism

5.Environmental impacts

6.Energy impacts

7.Equity impacts

8.Conclusion

References

1: Introduction

Global climate change and the mitigation of its adverse impacts is arguably one of the most critical issues facing humanity today. It has many dimensions and addressing them requires the insights from many disciplines—science, economics, society, governance, and ethics. The impacts of global warming will be around for decades, if not centuries. The discharges of gases from our extraction, processing, and use of fossil fuels are the major causes of the relatively recent rapid increase in global warming. Some of these gases, especially carbon dioxide, can remain in the atmosphere for hundreds of years. So even if all such gas emissions stopped, global warming and its adverse impacts will continue to be felt and affect us and our descendants. While we cannot stop global warming, we can control its rate of change.

The adverse impacts of global warming are felt in our economic and energy sectors, in the quality of our environment and in the functioning and health of our ecosystems. And we humans are part of our ecosystems. The pandemic caused by COVID-19 is also affecting our economy and our health, but because it has happened relatively quickly, and because its impact on our physical health is pronounced, dramatic, and undebatable, it got our attention and willingness to take measures to reduce its spread and find a cure. Not so for managing the causes of our warming climate. The adverse impacts resulting from the increase in global warming are multiple, major, and long term. They are changing the world we live in as well as affecting our health, but at rates that so far have not, with few exceptions, generated the political will needed to control it.

The aim of this chapter is to take a systems view of how climate change is impacting us and our planet and in turn how what we consume, and then discard or discharge into our environment, is impacting our climate. Focusing on these linkages and feedbacks among the various climatic, economic, ecologic, energy, and environmental components of this system may help us identify more comprehensive and effective approaches to addressing what the Oxford Dictionaries has called a climate emergency—a situation in which urgent action is required to reduce or halt climate change and avoid potentially irreversible environmental damage resulting from it (Ripple et al., 2020).

The section that follows first briefly reviews the causes of global warming and the physical impacts being observed today resulting from increasing temperatures. The next four sections focus on how global warming is impacting, and being impacted by, the world’s ecosystems, economies, energy sectors, and environments. The chapter ends with a discussion of how these impacts are inequitably distributed among the world’s countries and communities. The schematic in Fig. 1 illustrates the interdependencies among each of these system components.

Fig. 1

Fig. 1 The interdependent climate-economic-ecosystem- energy-environment-equity nexus.

2: Climate change

Changes in the earth’s climate have been happening relatively slowly. Over the last 650,000 years, ice glaciers have advanced and retreated, with the most recent one ending some 11,700 years ago. These changes are attributed to variations in Earth’s orbit and the resulting changes in the amount of solar energy reaching the Earth. Since the mid-20th century, the major cause of the relatively faster rate of warming is different. Rather than geophysical, it is anthropological. Scientists now consider the current rate of increase in global warming to be the result of human activities. Since the industrial revolution, we humans have learned we have the ability to dramatically alter the climate of our planet and at the global scale. Current increases in average global temperatures, as illustrated in Fig. 2, are now occurring roughly 10 times faster than the average rate of warming after the last ice age (NASA, 2020a).

Fig. 2Fig. 2

Fig. 2 (A) CO 2 concentrations over the last 800,000 years as measured from ice cores (blue/green) and directly (black). (B) Global surface temperature reconstruction over the last millennia using proxy data from tree rings, coral reefs, and ice cores, are shown in blue. Observational data is from 1880 to 2019. (A) Graph by Femke Nijsse [CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=69480542]. (B) Graph by Efbrazil [CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=87410053].

In the 1860s, physicist John Tyndall (shown in Fig. 3) recognized the impact of carbon dioxide, methane, and nitrous oxides gases on global temperatures. Their discharge into the atmosphere result from natural processes such as plant and animal respiration and volcano eruptions and through a variety of human activities. These activities include deforestation, land use changes, burning fossil fuels. Decomposition of wastes, the use of commercial and organic fertilizers, domestic livestock, soil and rice cultivation, manure management, nitric acid production, and biomass burning.

Fig. 3

Fig. 3 Physicist John Tyndall and his apparatus to investigate the heat-trapping properties of various gases. [https://en.wikipedia.org/wiki/John_Tyndall].

Some 30 years after Tyndall’s discovery, Swedish scientist Svante Arrhenius published a paper explaining how changes in the levels of carbon dioxide in the atmosphere could increase the Earth’s surface temperature (Graham, 2000). As such, carbon dioxide acts like a shield or greenhouse, preventing much of the sun’s reflected radiations from exiting the atmosphere. Indeed, as shown in Figs. 4–6, warming rates have increased, especially after the industrial revolution. Humans have increased atmospheric CO2 concentration by more than a third since the Industrial Revolution began. The agricultural, industrial, and transportation activities that support our economies have raised atmospheric carbon dioxide levels from preindustrial revolution 280–412 ppm.

Fig. 4

Fig. 4 Average global temperatures from 2010 to 2019 compared to a baseline average from 1951 to 1978. Source: https://data.giss.nasa.gov/gistemp/maps/index_v4.html [Public Domain https://en.wikipedia.org/wiki/Global_warming].

Fig. 5

Fig. 5 Observed temperature from NASA vs the 1850–1900 average used by the IPCC as a preindustrial baseline. The primary driver for increased global temperatures in the industrial era is human activity, with natural forces adding variability. Graph by Efbrazil [CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=87373456, https://en.wikipedia.org/wiki/Global_warming].

Fig. 6

Fig. 6 Three latitude bands that respectively cover 30%, 40%, and 30% of the global surface area show mutually distinct temperature growth patterns in recent decades. Graph by RCraig [CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid = 88086817].

As the adverse impacts from global warming became more evident, an increasing number of scientists and a few politicians began issuing urgent calls to reduce the rate of global warming. Today, much of scientific community, and informed general public, admit to the fact that humans are responsible for the increasing temperatures and that there are adverse impacts occurring throughout the world as a result of it (Leiserowitz et al., 2019). Yet the debate continues on when and just how to address this issue in an effective and equitable manner (Hansen et al., 2006, 2012; Gore, 2019; Martinich and Crimmins, 2019).

Most of the greenhouse gases we humans have discharged into the atmosphere have occurred in the past 35 years. What physical impacts have we observed over these past 35 years?

So far, our hotter atmosphere has resulted in:

•A warming Earth. As temperatures increase, what have been once-in-20-year extreme heat days may occur every 2 or 3 years on average. The 6 warmest years on record have occurred since 2014. In 2016, the months from January through September, with the exception of June, were the warmest on record (NASA, 2020c). The 10 warmest years of record (140 years) have occurred since 2005. The 6 warmest years are the 6 most recent years (IPCC, 2018).

•Warming oceans. Over 90% of the Earth’s warming that has happened during the past 50 years has occurred in the oceans (NASA, 2020c). Hotter oceans contribute to rising sea levels, ocean heat waves and coral bleaching, more intense storms, changes in marine life, and melting of ocean-terminating glaciers and ice sheets around Greenland and Antarctica (Dahlman and Lindsey, 2020). Last year, the oceans were warmer than any time since measurements began over 60 years ago (Berwyn, 2020; Cheng et al., 2020).

•Shrinking Ice Sheets. The Greenland ice sheet has lost an average of 286 billion tons of ice per year between 1993 and 2016. The Antarctica ice sheet lost about 127 billion tons of ice per year during the same time period. The rate of Antarctica ice mass loss has tripled in the last decade. The Arctic Ocean is expected to become essentially ice free in summer before mid-century (NASA, 2020b).

•Glacial retreat. Most of the world’s glaciers are retreating, including those in Africa and Alaska, the Alps, Andes, Himalayas, and the Rocky Mountains (WGMS, 2020; Pelto, 2015). Melting glaciers and ice sheets are the biggest cause of sea level rise in recent decades. Glacier loss is a serious threat to ecological and human water supplies in many parts of the world.

•Decreased snow cover. Satellite observations in the Northern Hemisphere over the past five decades show spring snow cover melting earlier and decreasing in extent (National Snow and Ice Data Center, 2019; NASA, 2013). The earlier decrease in snow cover increases surface temperatures and durations of growing seasons.

•Sea level rise. A warming of the oceans and the partially melting of the glaciers and other ice increases sea levels. Ocean water expands as it warms, contributing further to sea level rise. Global sea level rose about 20 cm in the last century. The rate of increase in the last two decades was twice that of the last century and this rate is increasing. Storm surges and high tides together with sea level rise and land subsidence increases the extent and frequency of flooding in many regions. Because of the delayed response to any change in global warming, sea levels are expected to rise well beyond this century (Nerem, et al., 2018; NASA, 2020c).

•Loss of Artic Sea Ice. Both the extent and thickness of Arctic sea ice has rapidly declined over the last several decades. The Arctic Ocean is expected to become essentially ice free in summer before mid-century (SNIDE, 2019; NASA, 2020c).

•More extreme hydrological and meteorological events. Since the middle of the previous century, the occurrence of record high temperature and rainfall intensity events has been increasing. The frequency of record low temperature events has been decreasing. Since the early 1980s the intensity, frequency, and duration of the hurricanes have increased. As the oceans continue to warm, hurricane-associated storm intensity and rainfall rates are expected to increase.

•Ocean acidification. Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30%. This increase is the result of humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the oceans. The rate of carbon dioxide absorbed by the upper layer of the oceans is increasing by about 2 billion tons per year (NOAA, 2020b; NASA, 2020c).

Depending on the extent to which greenhouse gas emissions are reduced over the next century we could sustain what remains of the Earth’s land mass and glaciers or, if current emission rates continue, achieve temperatures warmer than what can sustain life as we know it. Various scenarios, called representative concentration pathways (RPCs), are shown in Figs. 7 and 8 (NAS, 2020). RCP8.5 refers to the concentration of carbon that delivers global warming at an average of 8.5 W/m² across the planet.

Fig. 7

Fig. 7 Representative Concentration Pathways in terms of the concentration of carbon in the atmosphere at any date. The RCP 8.5 pathway delivers a temperature increase of about 4.3°C by 2100, relative to preindustrial temperatures, https://climatenexus.org/climate-change-news/rcp-8-5-business-as-usual-or-a-worst-case-scenario .

Fig. 8

Fig. 8 Average of climate model temperature projections for 2081–2100 relative to 1986–2005, under low and high emission scenarios, www.wikiwand.com/en/Regional_effects_of_global_warming .

Reports prepared by the Intergovernmental Panel on Climate Change (IPCC) tell us that we are on track for an eventual 3°C increase in average global warming. Their recommended goal is a maximum of 1.5°C but staying below 1.5°C will require rapid, far-reaching, and unprecedented changes in all aspects of society. Even a half of a degree above that recommended level may make the difference between a world with coral reefs and Arctic summer sea ice, and a world without them. To meet a goal of 1.5°C warming will require reductions in greenhouse gas emissions to 45% below 2010 levels by 2030. And as stated previously, even if all such emissions ceased today, the global temperature will continue to increase for decades, because of the cumulative effects in the atmosphere and oceans (USGCRP, 2017; IPCC, 2019).

Half of a degree doesn’t seem much, but this is an average increase over the entire globe. Making up those averages are the extremes that result in more frequent and intense heat waves as shown in Fig. 9, more damaging storms from both wind and rain, and higher oceans, as shown in Fig. 10. Life in this world will be affected differently, depending on where it is located. Species least able to adapt will face the greatest risks of extinction.

Fig. 9

Fig. 9 Locations that experienced extreme heat and humidity levels briefly (hottest 0.1% of daily maximum wet-bulb temperatures) from 1979 to 2017. Darker colors show more severe combinations of heat and humidity. Some areas have already experienced conditions at or near humans’ survivability limit of 35°C (95°F) ( Raymond et al., 2020).

Fig. 10

Fig. 10 Observed and projected changes in global mean sea level for 1800–2100. The boxes on the right show the very likely ranges in sea level rise by 2100 (relative to 2000) corresponding to three different representative concentration pathway scenarios. The lines above the boxes show possible increases based on newer research of the potential contribution to sea level rise from Antarctic ice melt. Data from the U.S. Global Research Program for the Fourth National Climate Assessment, https://nca2018.globalchange.gov/chapter/appendix-3#fig-A3-1.

Picture 10

3: Ecosystem impacts

Ecosystems are habitats that contain life. They range from wildlands free of human influence, to built environments totally designed and managed by humans. They include fresh and salt water bodies, wetlands, estuaries, forests, peatlands, terrestrial-coastal systems (e.g., mangroves and salt marshes), deserts, agricultural lands, and cities. The warming climate is impacting all of these habitats in multiple ways. On land, increasing temperatures are increasing precipitation variability and the probability of extreme dry and wet events leading to increasing physiological and hydrological stresses and the risks of wildfire. In the ocean, an increased occurrence of heatwaves and long-term trends of acidification increase the physiological stress experienced by many organisms. Interactions with other anthropogenic or natural stressors such as poaching, overfishing, invasive species, habitat fragmentation, direct degradation, or other measures that alter species populations, all tend to impact the sustainability of existing ecosystems and their resilience to climate change. Not only the warming itself but also the consequences of warming such as rising sea levels and more frequent and extreme flooding and droughts, and fires, also result in changes in plant and animal composition and in predator-prey and food chain relationships.

The resulting changes in these habitats can alter the products and services provided by them, such as food, fuel, timber, water, clean air, and medicines as well as their aesthetic or cultural value. Other examples include reefs and barrier islands that protect coastal developments from storm surges, wetlands that absorb floodwaters, and cyclical wildfires that clear excess forest debris and reduce the risk of larger more damaging fires (NAS, 2019). Shifts in ecological conditions from warming can support the spread of pathogens, parasites, and diseases that could impose serious effects on human health and income. For example, the oyster parasite, Perkinsus marinus, is causing large oyster die-offs. This parasite has extended its range northward along the Atlantic coast of the US because of increasing winter temperatures (Marquis et al., 2020).

Warming can cause both animal and plant species to migrate to habitats more suited to their survival. Patterns of animal and plant migration, breeding, pest avoidance, and food availability can be affected in different ways. Different species differ in their ability to adjust and adapt. For many species, the climate’s temperature influences where they live and key stages of their life cycle. As winters become shorter and milder, the timing of these life cycle events can change.

As temperatures increase, the habitat ranges of many species are shifting to cooler elevations. For some species, it means movement into less hospitable habitat, increased competition, and/or range reduction. For some others it has led to local extinctions. For example, boreal forests are invading tundra, reducing habitat for the many unique species that depend on the tundra, such as caribou, arctic foxes, and snowy owls. Other observed changes include a shift in the range boundaries of shrub lands and broadleaf and conifer forests. As rivers and streams warm, warm water fish are expanding into areas previously inhabited by coldwater species. Coldwater fish, including many highly valued species, are losing their habitat. Decreases in the duration and extent of Artic sea ice has led to declines in ice algae that are eaten by zooplankton, which are then eaten by Arctic cod, an important food source for many marine mammals, including seals. Seals are eaten by polar bears. Thus, the loss of sea ice can ultimately affect survival of polar bears (Malhi et al., 2020).

3.1: Agricultural ecosystems

Agricultural ecosystems cover almost 40% of Earth’s land area. About 11% is cultivated, and approximately 27% is permanent