Climate stability

Lane Kenworthy, The Good Society
February 2024

We are causing Earth to warm. What are the potential consequences? What should we do about it?

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HUMAN-CAUSED CLIMATE CHANGE

In various ways, but especially by burning fossil fuels, we’ve dramatically increased greenhouse gas emissions. If the amount of greenhouse gases emitted from earth is larger than natural processes can remove, it will trap more infrared radiation (sunlight that bounces off the earth) in the atmosphere, leading to a rise in temperature. Also, warm air holds more water vapor than cold air, and water vapor causes additional trapping of heat. The planet should therefore be warming.

What does the evidence say?

Begin with the hypothesized cause. As figure 1 shows, emissions of carbon dioxide have increased steadily since 1750, when the industrial revolution began, and the rise has been especially pronounced since 1950.

Figure 1. Carbon dioxide emissions
Billions of tonnes of carbon dioxide. Includes emissions from the consumption of fossil fuels (from coal, oil, gas, and flaring) plus direct industrial emissions from cement. Doesn’t include emissions from land use change. Data source: Our World in Data, “Annual CO2 Emissions,” using data from the Global Carbon Project.

As emissions of carbon dioxide have increased, the amount in the atmosphere has increased. We have direct measurement of carbon dioxide atmospheric concentration only since 1959, but data from ice core drilling in Antarctica suggest that in the 800,000 years prior to 1750, it never exceeded 300 ppm (parts per million). Between 1750 and 1959 it rose from 280 to 316. As figure 2 indicates, between 1959 and 2023 it increased from 316 to 421.1

Figure 2. Carbon dioxide concentration in the atmosphere
Parts per million. 280 is the estimated level in 1750. Data source: Earth System Research Laboratory, National Oceanic and Atmospheric Administration, US Department of Commerce, esrl.noaa.gov/gmd/ccgg/trends.

Carbon dioxide isn’t the only problematic greenhouse gas. Methane and nitrous oxide play a role too. Here a major contributor is the raising of animals for food, which accounts for 10-25% of all greenhouse gas emissions.2 Figure 3 shows that methane concentration in the atmosphere has increased sharply since scientists began measuring it in the mid-1980s. The concentration of methane is much lower than of carbon dioxide, but methane’s potency as a greenhouse gas is about 30 times greater.3

Figure 3. Methane concentration in the atmosphere
Parts per billion. 680 is the estimated level in 1750. Data source: Earth System Research Laboratory, National Oceanic and Atmospheric Administration, US Department of Commerce, esrl.noaa.gov/gmd/ccgg/trends_ch4.

Next, the hypothesized effect. Has the planet’s temperature increased? Yes, it has. Figure 4 shows direct measurements beginning in the mid-1800s. Average temperature has risen sharply, particularly since 1950. Figure 5 shows indirect and direct measurements going back to 700. It suggests a similar conclusion.4

Figure 4. Earth’s average temperature
Difference from the 1901-2000 average. Degrees Celcius. Land and ocean. Data source: National Centers for Environmental Information, National Oceanic and Atmospheric Administration, ncdc.noaa.gov/cag/time-series/global. The line is a loess curve.

Figure 5. Earth’s average temperature
Source: New York Times, using data from the Intergovernmental Panel on Climate Change.

Could the observed temperature rise be a result of something else?5 Probably not. Computer simulations that project temperature patterns in scenarios with little or no human emission of greenhouse gases don’t come close to matching the earth’s actual temperature patterns. As figure 6 shows, when the simulations add human-generated greenhouse gases, they closely match the observed temperature patterns.6

Figure 6. Predicted temperature and actual temperature
The predicted temperature, shown in red, is based on levels of carbon dioxide in the atmosphere and volcanic activity. The actual temperature, shown in black, is the average land surface temperature for the planet (degrees Celsius), ten-year moving average. Source: Berkeley Earth Surface Temperature (BEST) project, “Summary of Results,” 2013

The most thorough survey of the evidence is in reports by the Intergovernmental Panel on Climate Change (IPCC), the most recent of which concludes that “Human activities, principally through emissions of greenhouse gases, have unequivocally caused global warming.”7 Among climate scientists, surveys consistently find more than 90% agreement that humans are causing climate change.8 A 2014 report by the Climate Change Panel of the American Association for the Advancement of Science described the scientific consensus this way: “The science linking human activities to climate change is analogous to the science linking smoking to lung and cardiovascular diseases. Physicians, cardiovascular scientists, public health experts, and others all agree smoking causes cancer. And this consensus among the health community has convinced most Americans that the health risks from smoking are real. A similar consensus now exists among climate scientists, a consensus that maintains climate change is happening, and human activity is the cause.”9

CONSEQUENCES

Climate change is likely to have an array of effects. Many are difficult to project, because the climate is a complex system and because it isn’t clear how much progress we will make in slowing or reversing the carbonization of the atmosphere.

In the absence of quick and effective action to reduce greenhouse gas emissions, climate change is likely to have damaging effects on health via, among other things, heat waves, urban smog, lack of access to water, rising food prices, and displacement.10 In the United States, for example, the number of 100-degree-or-more days per year would increase significantly almost everywhere, and by the end of the century a good bit of the country would have summer weather similar to today’s Texas and Arizona, as we see in figure 7. In some parts of the world, things would be worse. The World Heath Organization projects that if we don’t slow climate change, by 2050 an additional 250,000 people (0.002% of the world’s population) will die each year directly due to greater heat.11

Figure 7. Number of days above 100 degrees if greenhouse gas emission trends were to continue unabated
Fahrenheit. Source: Heidi Cullen, “Think It’s Hot Now? Just Wait,” New York Times, 2016, using projections by the World Climate Research Program.

Climate change will increase the frequency and intensity of weather events and weather-related events — storms (hurricanes, typhoons, tornadoes), floods, droughts, fires. Figure 8 shows that extreme rainstorms, one type of event for which we have a lengthy data series, have become more common in the United States. Figure 9 shows that extreme fires have become increasingly common in California since 1990.

Figure 8. Extreme rainstorms
Share of US weather stations experiencing an extreme rainstorm in a year (10-year average). The definition of “extreme” varies by region, depending on typical rainfall. Data source: David Leonhardt, “Irma, and the Rise of Extreme Rain,” New York Times, 2017, using data from Kenneth Kunkel, North Carolina Institute for Climate Studies.

Figure 9. Extreme fires in California
Number of acres burned. “m” = million. The data are from federal and state (not local) firefighting. Data source: New York Times. The line is a loess curve.

The most significant impact of warming could come via melting of the Greenland and West Antarctic ice sheets, each of which has enough ice to raise sea levels by 15 to 20 feet. A significant rise in sea level could threaten hundreds of millions of people who live in coastal areas. The United Nations estimates that by 2050 as many as 1 billion people, or 10% of the world’s population, may be climate migrants.12 Predicting how much the two ice sheets will melt and what impact that will have is extremely difficult. In its 2013 report, the IPCC concluded that melting from the two ice sheets may cause a sea level rise of 1 to 3 feet by the year 2100. Since then, scientists have discovered that ice loss in the Greenland and West Antarctic ice sheets has been faster in recent years than previously thought and that a large glacier in the East Antarctic ice sheet is now vulnerable to melting. According to one knowledgable observer, these recent findings “have led top climatologists to conclude that we are likely headed toward what used to be the high-end of projected global sea-level rise this century (i.e., 4 to 5 feet) and that the worst-case scenarios where humanity fails to take aggressive action to cut greenhouse gas emissions are considerably higher than that.”13

Most ominously, Gernot Wagner and Martin Weitzman estimate that in the absence of significant policy change there is perhaps a one in ten chance that the globe’s average temperature will rise by 6°C or more.14 The consequences could be quite grim, as David Wallace-Wells explains15:

The earth has experienced five mass extinctions …, each so complete a wiping of the fossil record that it functioned as an evolutionary reset, the planet’s phylogenetic tree first expanding, then collapsing, at intervals, like a lung: 86 percent of all species dead, 450 million years ago; 70 million years later, 75 percent; 125 million years later, 96 percent; 50 million years later, 80 percent; 135 million years after that, 75 percent again. Unless you are a teenager, you probably read in your high school textbooks that these extinctions were the result of asteroids. In fact, all but the one that killed the dinosaurs involved climate change produced by greenhouse gas. The most notorious was 250 million years ago; it began when carbon dioxide warmed the planet by five degrees Celsius, accelerated when that warming triggered the release of methane, another greenhouse gas, and ended with all but a sliver of life on Earth dead.

WHAT SHOULD WE DO?

There is considerable uncertainty about the speed and scale of climate change’s consequences for the planet and for humans and other animals. While some see this uncertainty as a reason to focus on other problems where we have more knowledge about the efficacy of action and/or where the payoff will be immediate,16 our typical approach to problems where the outcome is uncertain but potentially very bad is to use extreme precaution in order to prevent them.17 Think of World War II, disease outbreaks, terrorism, or the “reasonable doubt” principal we use in criminal trials.

How much reduction in greenhouse gas emissions do we need? Many climate scientists believe we should aim for an increase in average temperature of no more than 1.5°C or at most 2°C (it’s already risen about 1°C). Not too long ago, knowledgeable observers calculated that this would require reducing greenhouse gas emissions by more than half by 2050 and to zero by 2100.18 More recent calculations suggest we need to move faster, cutting emissions in half by 2030 and to zero by 2050.19

How can we do it? Advocates frequently emphasize personal behaviors and lifestyles, but the key is to change large-scale actors, institutions, and systems.20

Shift from fossil fuel energy to clean energy. Government could require the phase-out of fossil fuel energy sources by a particular date, but the most common policy tools here are carbon taxes and cap-and-trade programs. Sweden and Norway have had a carbon tax since the early 1990s, and the Canadian province of British Columbia has had one since 2008. The United States used cap-and-trade programs to successfully deal with leaded gasoline in the 1980s and acid rain pollution in the 1990s. California began a cap-and-trade program to reduce greenhouse gas emissions in 2013.21 Quebec and Ontario also have cap-and-trade programs for greenhouse gases. If necessary, government could purchase a majority stake in fossil fuel companies and rapidly reduce coal, oil, and gas production.22 To this point, congressional Republicans have blocked federal government action in the US.23

Government policy also can help by purchasing clean energy and by offering short-term price guarantees. Both steps can help encourage additional private investment in clean-energy firms and enable those firms to remain in business long enough to gain a foothold in the market.24

Humans currently use, in total, about 160,000 terawatt hours of energy per year.25 There is more than enough energy available from solar and wind, the two leading noncarbon (“renewable”) energy resources, to provide this amount and more.26 The challenge is getting it to everyone throughout the year and throughout the day. For that, we need further improvement in storage and batteries. An important advantage, however, particularly for solar energy, is that it can be generated close to where it is needed — on the roofs of buildings, houses, and parking lots. And because it is much more efficient than fossil fuel energy sources, one estimate concludes that “without changing the size of our homes, or our cars, or fundamentally changing the fabric of our lives, a fully electrified energy economy using non-carbon fuel sources would require less than half of the total amount of energy we use today.”27

The remainder of the needed noncarbon energy can be provided by a mix of hydroelectric, biofuels, geothermal, and nuclear.28

The United States accounts for about one-fifth of worldwide carbon emissions, so we could help a lot even if we act alone.29 Better would be an international agreement that reduces emissions in other countries too. Efforts over the past several decades haven’t been very successful, though the 2015 Paris Climate Accord offered some grounds for optimism.30 An alternative to voluntary agreements, which are vulnerable to free riding, is the idea of a “climate club.” According to William Nordhaus, “Under the club rules, participating countries would undertake harmonized but costly emissions reductions…. Countries who are outside the club — and do not share in the burden of emissions reductions — are penalized…. Economic modeling indicates that the most promising penalty is uniform percentage targets on the imports of nonparticipants into the club region. A country considering whether to undertake costly abatement would have to weigh those costs against the potentially larger costs of reduced trade with countries in the club.”31

What exactly must be done in order to get to net zero emissions by mid-century? A 2021 report by the International Energy Agency offers some concrete guidance32:

This year, nations would stop approving new coal plants unless they are outfitted with carbon capture technology to trap and bury their emissions underground. Nations would also stop approving the development of new oil and gas fields beyond those already committed.

By 2025, governments worldwide would start banning the sale of new oil and gas furnaces to heat buildings, shifting instead to cleaner electric heat pumps.

By 2030, electric vehicles would make up 60 percent of new car sales globally, up from just 5 percent today. By 2035, automakers would stop selling new gasoline- or diesel-fueled passenger vehicles. By 2050, virtually all cars on the roads worldwide either run on batteries or hydrogen.

By 2035, the world’s advanced economies would zero out emissions from power plants, shifting away from emitting coal and gas plants to technologies like wind, solar, nuclear, or carbon capture. By 2040, all of the world’s remaining coal-fired power plants are closed or retrofitted with carbon capture technology.

In 2035, more than half of new heavy trucks would be electric. By 2040, roughly half of all air travel worldwide would be fueled by cleaner alternatives to jet fuel, such as sustainable biofuels or hydrogen.

Geoengineering. We can try to alter the earth and/or its biosphere. One approach aims to limit the warming of the planet. The main idea here is to deflect more sunlight, for example by injecting large quantities of aerosols into the stratosphere. This is at best a partial approach, as it wouldn’t stop or even slow carbonization, but it might buy us some time. A second approach is to actually remove carbon from the atmosphere. In a pair of reports issued in 2015, the US National Academy of Sciences concluded that while geoengineering efforts are worth further exploration, “There is no substitute for dramatic reductions in the emissions of carbon dioxide and other greenhouse gases to mitigate the negative consequences of climate change.”33

Research. A rapid shift to noncarbon energy sources is feasible with existing technology. But this problem is so big, and political obstacles to rapid decarbonization are so formidable, that it makes sense to invest heavily in development of new energy sources, new methods of delivery, new ways of getting carbon out of the atmosphere, and more.34

DOES SAVING THE PLANET REQUIRE SACRIFICING QUALITY OF LIFE?

The shift to a decarbonized world is often portrayed as a sacrifice — a reduction in our quality of life in order to save the only planet on which, as far as we can tell, human life is possible. But that’s probably the wrong image. If conversion to 100% noncarbon energy is done chiefly via electrification, the main changes in our lives will be driving electric (instead of internal combustion engine) cars, using an electric (instead of gas) cooking source, getting heating from an electric heat pump (instead of gas-powered forced air), and eating more plant-based foods. Even for those who live in rich countries, much of this will be an improvement in quality of life, not a downgrade. And for people in middle- and low-income nations, it will be an unequivocal advance.35

How much will it cost us? Current estimates are in the range of 1% to 3% of GDP.36 (This means economic growth will be a bit slower. It doesn’t mean economic growth will stop or turn negative.) That’s a small price to pay for saving the planet. Moreover, not acting might be just as costly. According to one respected estimate, by William Nordhaus, the loss from a rise in temperature of 2.5°C would be about 2% of global GDP.37

And greening the economy will boost employment. In the United States, the number of jobs added net of fossil-fuel-related ones lost is estimated to be 2.5 to 4 million per year, or about 2% of current employment.38

How will we pay for it? Saul Griffith estimates that in the United States the average cost of switching to clean-sourced electricity would be about $40,000 per household. Mainly that means replacing internal-combustion-engine cars with electric ones, replacing natural gas heating systems with an electric heat pump, and powering stoves and clothes dryers with electricity rather than gas. That amount is too much for many households to afford, but a new program of 20-year government-guaranteed loans, similar to the program that created and backstopped 30-year home mortgage loans beginning in the 1930s, would enable every household to afford this.39

SOME CAUSE FOR HOPE

There are a number of encouraging technological and political developments.40

As of 2021, wind and solar account for 10% of worldwide electricity. In the 2010s, the cost of solar panels fell by nearly 90% and the cost of wind turbines by 60%. Clean energy is now cheaper than 40% of coal plants worldwide and most natural gas plants. The share of electricity provided by solar and wind increased by 20% per year in the 2010s. If that rate of increase continues, solar and wind will account for 40% of electricity in 2030, putting the electricity sector on track to reach net zero by 2040.

The key technological challenge is getting electricity from solar and wind energy to everyone throughout the year and throughout the day. Here an important advantage, particularly for solar, is that it can be generated close to where it is needed — on the roofs of buildings, houses, and parking lots. Sill, we’ll likely need further improvement in storage and batteries. Or, given that the cost of producing clean energy is likely to continue to decrease, we could simply create enough overcapacity that we generate a sufficient supply, even during the lowest point in the year, to exceed demand. One reason this latter strategy is potentially doable is that clean energy is much more efficient than energy from fossil fuels.

The cost of batteries for electric cars is expected to reach parity with internal combustion engines by the early 2020s. And Toyota says it has developed a new solid-state (rather than lithium-ion) battery for electric vehicles that will allow a car to travel 700-plus miles on a charge that takes 10 minutes. Sales of internal-combustion vehicles have been declining since 2017. The European Union, California, and New York will prohibit sales of new cars with internal combustion engines beginning in 2035. Fiat and Ford (in Europe) have pledged to sell only zero-emission vehicles by 2030, General Motors by 2035, and Honda by 2040.

Signatories to the 2015 Paris Climate Accord, including 197 nations, pledged to take action to hold “the increase in the global average temperature to well below 2°C above preindustrial levels and to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels.” The Accord didn’t commit any country to particular actions. Nor did it specify rewards or punishments.

In 2021, 105 countries signed an agreement to cut methane emissions by 30% by 2030. This too didn’t commit any nation to particular actions or specify rewards or punishments.

Since 2015 a small but growing number of countries — Norway, Sweden, France, New Zealand, the United Kingdom, Canada, Japan, South Korea — have passed laws requiring zero net greenhouse gas emissions (“carbon neutrality”) by 2050. In 2021, the US president issued an executive order instructing the country to reach zero net emissions by 2050. In 2020 China’s government pledged to reach carbon neutrality by 2060, and in 2021 India’s pledged to do so by 2070.

A small but growing number of US states have passed laws requiring large reductions in greenhouse gas emissions by 2050. In 2019, California, which has the world’s fifth largest economy, passed a law mandating zero net carbon emissions in the state’s electricity sector by 2045, and its governor issued an executive order requiring zero net emissions across the entire economy by the same year. In 2019, New York state passed a law mandating 85% reduction in greenhouse gas emissions (from 1990 levels) by 2050.

In 2019, the Netherlands’ Supreme Court ruled that the European Convention on Human Rights requires the Dutch government to significantly reduce the country’s greenhouse gas emissions — to 25% below the 1990 level by 2020. This was the first time a court required a nation to take action against climate change. In 2021, Germany’s Federal Constitutional Court required the German government to make its climate law more aggressive in order to comply with commitments made in the 2015 Paris Climate Accord.

Climate Trace, a coalition of nonprofits and businesses, uses artificial intelligence, machine learning, and satellite image processing to measure worldwide greenhouse gas emissions in real time, with updates every six hours. This kind of accurate, up-to-date information should help voters, activists, and other actors to monitor governments and corporations and apply pressure where appropriate.

HOW MUCH WARMING WILL THERE BE?

Climate Action Tracker’s most recent calculations project that current policies will lead to warming of 2.5 to 2.9 degrees (“policies and action” scenario in figure 10). That’s higher than we want, but it’s an improvement compared to the estimate as of 2015, which was 3.7 degrees. If countries that have pledged or are considering pledging to get to net zero emissions by the middle of this century actually meet that target, Climate Action Tracker estimates warming will be limited to 1.8 degrees (“optimistic scenario” in figure 10).41

Figure 10. Global warming projections under various scenarios
Source: Climate Action Tracker, “Temperatures,” December 2023.

SUMMARY

The hypothesis that greenhouse gas emissions are causing climate change is compelling. The evidence in support of the hypothesis is very strong, and there is near-consensus among experts about this.

Though it is difficult to predict the magnitude or speed of the consequences with much precision, there will be an increase in dangerous weather events and deaths. At the same time, we’ve begun to make progress, and under current policies the rise in temperature is estimated to end up being in the range of 2 to 3 degrees Celsius, which won’t end human life on this planet. And better policies can push that number even lower.

The most compelling strategy is to electrify everything and to produce that electricity with clean energy, primarily solar and wind.

APPENDIX

The appendix has additional data.

  1. Carbon Dioxide Information Analysis Center, “800,000-year Ice-Core Records of Atmospheric Carbon Dioxide”; Earth System Research Laboratory, National Oceanic and Atmospheric Administration, “Trends in Atmospheric Carbon Dioxide”; Intergovernmental Panel on Climate Change (IPCC), “Working Group 1 Summary for Policymakers,” Fifth Assessment Report, 2013, p. 7; Wikipedia, “Carbon Dioxide in Earth’s Atmosphere.” ↩︎
  2. P.J. Gerber et al, Tackling Climate Change Through Livestock: A Global Assessment of Emissions and Mitigation Opportunities, Food and Agriculture Organization of the United Nations, 2013. See also Natasha Gilbert, “One-Third of Our Greenhouse Gas Emissions Come from Agriculture,” Nature, 2012; Rob Bailey, Antony Froggatt and Laura Wellesley, “Livestock: Climate Change’s Forgotten Sector,” Research Paper, Chatham House, 2014; J. Poore and T. Nemecek, Reducing Food’s Environmental Impacts Through Producers and Consumers,” Science, 2018; Ecofys, “World Greenhouse Gas Emissions Flow Chart”; Julia Moskin, Brad Plumer, Rebecca Lieberman, and Eden Weingart, “Your Questions About Food and Climate Change, Answered,” New York Times, 2019; Environmental Protection Agency, “Sources of Greenhouse Gas Emissions”. ↩︎
  3. Wikipedia, “Atmospheric Methane.” ↩︎
  4. Because the historical temperature records are incomplete, scientists introduce corrections. Are these corrections biased? This was the concern at the heart of the 2009 “climategate” controversy. However, the Berkeley Earth Surface Temperature (BEST) project has gathered together all existing temperature measures, and the data, even with no corrections, show a similar trend. R. Rohde, R.A. Muller, R. Jacobsen, E. Muller, S. Perlmutter, et al, “A New Estimate of the Average Earth Surface Land Temperature Spanning 1753 to 2011,” Geoinformatics and Geostatistics: An Overview, 2013. ↩︎
  5. For example, could this be a “heat island” effect? In other words, do these measurements show warming simply because a number of the temperature stations are near towns that have been growing? No. We know this for three reasons: a heat island effect would be strongest on still nights, yet trends from data recorded on still nights are similar to those on windy nights; temperature readings from non-heat-island stations show a similar trend to those from heat-island stations; and the temperature of water at the surface of oceans shows a similar trend to that on land. “The Science of Climate Change,” The Economist, 2010; C. Wickham, R. Rohde, R.A. Muller, J. Wurtele, J. Curry, et al., “Influence of Urban Heating on the Global Temperature Land Average using Rural Sites Identified from MODIS Classifications,” Geoinformatics and Geostatistics: An Overview, 2013. ↩︎
  6. Also, as Joseph Romm has noted, “if the warming is caused by an increase in greenhouse gases, we expect the lower atmosphere (troposphere) to warm, the upper atmosphere (stratosphere) to cool, and the boundary between them (tropopause) to rise. All of this has been observed. If recent warming were due to increases in the intensity of radiation from the sun, then in addition to the troposphere, the stratosphere should be warming, too, which is not happening.” Joseph Romm, Climate Change: What Everyone Needs to Know, Oxford University Press, 2016, p. 10. ↩︎
  7. Intergovernmental Panel on Climate Change, “Summary for Policymakers,” Sixth Assessment Report (AR6), 2023, p. 4. William Nordhaus points out that “Scientists are increasingly confident that the basic results of climate modeling are accurate. Climate models calculate that past emissions have contributed to warming of almost one degree centigrade over the last century, with rapid continued warming projected over the present century and beyond. In its 2001 report, the Intergovernmental Panel on Climate Change reported that human activity was ‘likely’ to be the source of this warming. The IPCC upgraded this evaluation to ‘very likely’ in its 2007 report and to ‘extremely likely’ in its 2013 report.” Nordhaus, “A New Solution: The Climate Club,” New York Review of Books, 2015. ↩︎
  8. William R.L. Anderegg, James W. Prall, Jacob Harold, and Stephen H. Schneider, “Expert Credibility in Climate Change,” Proceedings of the National Academy of Sciences, 2010; John Cook et al, “Consensus on Consensus: A Synthesis of Consensus Estimates on Human-Caused Global Warming,” Environmental Research Letters, 2016. ↩︎
  9. Climate Change Panel, American Association for the Advancement of Science, What We Know: The Reality, Risks, and Response to Climate Change, 2014, p. 2. ↩︎
  10. Romm, Climate Change. ↩︎
  11. World Health Organization, “Quantitative Risk Assessment of the Effects of Climate Change on Selected Causes of Death, 2030s and 2050s,” 2014, p.21. ↩︎
  12. International Organization for Migration, “IOM Outlook on Migration, Environment, and Climate Change,” 2014, p. 38. ↩︎
  13. IPCC, “Working Group 1 Summary for Policymakers,” Fifth Assessment Report, pp. 18, 21; Potsdam Institute for Climate Impact Research and Climate Analytics, “Turn Down the Heat: Why a 4°C Warmer World Must Be Avoided,” The World Bank, 2012; Romm, Climate Change, p. 94. ↩︎
  14. Gernot Wagner and Martin L. Weitzman, Climate Shock: The Economic Consequences of a Hotter Planet, Princeton University Press, 2015, ch. 3. See also Steven C. Sherwood and Matthew Huber, “An Adaptability Limit to Global Warming Due to Heat Stress,” Proceedings of the National Academy of Sciences, 2010. ↩︎
  15. David Wallace-Wells, The Uninhabitable Earth, Duggan Books, 2019, pp. 3-4. ↩︎
  16. Bjorn Lomborg, Cool It, Random House, 2007. ↩︎
  17. Martin L. Weitzman, “Fat-Tailed Uncertainty in the Economics of Catastrophic Climate Change,” Review of Environmental Economics and Policy, 2011; Gernot and Weitzman, Climate Shock. ↩︎
  18. Romm, Climate Change, p. 154. ↩︎
  19. Jesse D. Jenkins and Samuel Thernstrom, “Deep Decarbonization of the Electric Power Sector: Insights from Recent Literature,” Energy Information Reform Project, 2017; Intergovernmental Panel on Climate Change (IPCC), “Summary for Policymakers of IPCC Special Report on Global Warming of 1.5°C,” 2018; Saul Griffith, Electrify, MIT Press, 2021. ↩︎
  20. Emma Marris, “How to Stop Freaking Out and Tackle Climate Change,” New York Times, 2019; Griffith, Electrify. ↩︎
  21. Center for Climate and Energy Solutions, “California Cap-and-Trace”; Jennifer Medina and Matt Richtel, “Carbon Goal in California Is ‘Milestone’ on Climate,” New York Times, 2016; Brad Plumer, “How California Plans to Go Far Beyond Any Other State on Climate,” New York Times, 2017. ↩︎
  22. Kate Aronoff, Alyssa Battistoni, Daniel Aldana Cohen, and Thea Riofrancos, A Planet to Win: Why We Need a Green New Deal, Verso, 2019. ↩︎
  23. “Harry Reid: Senate Will Abandon Cap-and-Trade Energy Reform,” Christian Science Monitor, 2010. ↩︎
  24. Chomsky and Pollin, Climate Crisis and the Global Green New Deal, ch. 3. ↩︎
  25. Hannah Ritchie and Max Roser, “How Much Energy Does the World Consume?,” Our World in Data. Estimates from the International Energy Agency, the US Energy Information Administration, and the World Bank are similar. ↩︎
  26. Mark Z. Jacobson et al, “100% Clean and Renewable Wind, Water, and Sunlight All-Sector Energy Roadmaps for 139 Countries of the World,” Joule, 2017; Griffith, Electrify. ↩︎
  27. Griffith, Electrify. ↩︎
  28. Inês Azevedo, Michael R. Davidson, Jesse D. Jenkins, Valerie J. Karplus, and David G. Victor, “The Paths to Net Zero,” Foreign Affairs, 2020. ↩︎
  29. Environmental Protection Agency, “Global Greenhouse Gas Emissions Data.” ↩︎
  30. “Climate Talks End with Modest Deal on Emissions,” New York Times, 2010; “Nations Approve Landmark Climate Accord in Paris,” New York Times, 2015. ↩︎
  31. Nordhaus, “A New Solution: The Climate Club.” ↩︎
  32. Brad Plumer, “Nations Must Drop Fossil Fuels, Fast, World Energy Body Warns,” New York Times, 2021. ↩︎
  33. National Research Council, Committee on Geoengineering Climate, “News Release,” 2015. ↩︎
  34. Ted Norhaus and Michael Shellenberger, Break Through, Houghton Mifflin, 2007; Jim Manzi, “Keeping Our Cool: What to Do about Global Warming,” Cato Unbound, 2008; Romm, Climate Change; Kevin Drum, “We Need a Massive Climate War Effort — Now,” Mother Jones, 2019. ↩︎
  35. Griffith, Electrify. ↩︎
  36. Jeffrey Sachs et al, America’s Zero Carbon Action Plan, Sustainable Development Solutions Network, 2020, p. 19; Noam Chomsky and Robert Pollin, Climate Crisis and the Global Green New Deal, Verso, p. 74. ↩︎
  37. Paul Krugman, “Building a Green Economy,” New York Times, 2010; William D. Nordhaus, “Why the Global Warming Skeptics Are Wrong,” New York Review of Books, 2012. ↩︎
  38. Sachs et al, America’s Zero Carbon Action Plan, p. 5. ↩︎
  39. Griffith, Electrify. ↩︎
  40. Wikipedia, “Paris Agreement”; Wikipedia, “Carbon Neutrality”; Megan Darby, “Which Countries Have a Net Zero Carbon Goal,” Climate Home News, 2019; NRDC, “Unpacking New York’s Big New Climate Bill: A Primer,” 2019; Brady Dennis, “Countries Must Ramp Up Climate Pledges by 80 Percent to Hit Key Paris Target, Study Finds,” Washington Post, 2021; The Economist, “A Court Ruling Triggers a Big Change in Germany’s Climate Policy,” 2021; Al Gore “Where I Find Hope,” New York Times, 2020; International Energy Agency, Net Zero by 2050, 2021; Neal E. Boudette and Coral Davenport, “G.M. Will Sell Only Zero-Emission Vehicles by 2035,” New York Times, 2021; Neal E. Boudette and Jack Ewing, ”Ford Says It Will Phase Out Gasoline-Powered Vehicles in Europe,” New York Times, 2021; Dave Jones, “Global Electricity Review 2022,” Ember, 2022; Melissa Eddy, “E.U. to Ban New Cars Powered by Gasoline,” New York Times, 2023; Liam Denning, “Toyota May Yet Do a Tesla and Upend EVs,” Bloomberg Opinion, 2023. ↩︎
  41. See also International Energy Agency, “Scenario Trajectories and Temperature Outcomes,” World Energy Outlook, 2021; Malte Meinshausen et al, “Realization of Paris Agreement Pledges May Limit Warming Just Below 2°C,” Nature, 2022. ↩︎