By Roberta Attanasio, IEAM Blog Editor
Climate change is reshaping our planet—not only in its physically measurable aspects, but also in terms of humanitarian challenges. Melting glaciers, rising seas, flooding, heat waves and the like are accompanied by human displacement and migration, changes in the occurrence of infectious diseases and—as highlighted by a recent study—the intensification of global economic inequality over the past half-century.
According to a study published 22 April 2019 in the Proceedings of the National Academy of Sciences, the difference between the world’s richest and poorest countries is 25% larger today than it would have been without global warming. Lead author Noah Diffenbaugh said: “Our results show that most of the poorest countries on Earth are considerably poorer than they would have been without global warming. At the same time, the majority of rich countries are richer than they would have been.” Marshall Burke, co-author, added that for the poorest countries, “This is on par with the decline in economic output seen in the U.S. during the Great Depression. It’s a huge loss compared to where these countries would have been otherwise.”
The study, based on data from 1961–2010, builds on research published by the authors in 2018. By analyzing annual temperatures along with a measure of the average person’s economic standard of living—the Gross Domestic Product (GDP) per capita (per person)—they estimated the effects of temperature fluctuations on economic growth, showing that productivity peaks at an annual average temperature of 13°C, and declines at higher temperatures. Accordingly, they also showed that growth during warmer than average years has accelerated in cool nations while slowing in warm nations and estimated that, by 2100, climate change could reduce overall global economic output by 23%.
For the new study, they expanded their research by using more than 20 climate models developed by research centers around the world, thus estimating what each country’s GDP per capita would have been without the effects of warming temperatures. To account for uncertainty, the researchers calculated more than 20,000 versions of what each country’s annual economic growth rate could have been without global warming and provided estimates that capture the range of outcomes derived from those versions. They found that there is uncertainty in whether historical warming has benefited some temperate, rich countries. However, for most countries, it’s quite certain that global warming has either helped or hurt economic growth. For most poor countries, especially those close to the equator, there is a >90% likelihood that per capita GDP is lower today than if global warming had not occurred. Indeed, for these countries, even a slight increase in temperature may result in devastating effects on human health, labor productivity, and agricultural yield among others.
Researchers and policy makers have been aware for the past several years that the poorest populations would experience the greatest impacts of local climate changes. For example, a report released last November by 13 US federal agencies suggested that a warming planet could cause a major negative effect on the country’s GDP, dissolving as much as 10% of the American economy by the end of the century. However, the 2019 study actually quantifies these changes.
Notably, their study points out exactly how much each country has been impacted economically by global warming, relative to its historical greenhouse gas contributions. While the biggest emitters enjoy on average about 10% higher per capita GDP today than they would have in a world without warming, it is the lowest emitters that have been reduced by 25%. The negative economic impact is 31% for India, 29% for Nigeria, and 25% for Brazil, whereas countries that gained from global warming include Canada and Norway, which experienced a 32% and 34% increase in per capita GDP, respectively, when compared with a world without climate change. For other countries, including China and the US, the impact on per capita GDP was minimal. As Somini Sengupta says, “Climate change creates winners and losers. Norway is among the winners; Nigeria among the losers.”
Diffenbaugh and Burke conclude that “in addition to not sharing equally in the direct benefits of fossil fuel use, many poor countries have been significantly harmed by the warming arising from wealthy countries’ energy consumption.”