Climate Change Could Cost The U.S. Up To 10.5 Percent Of Its GDP By 2100, Study Finds

Washington Post - Andrew Freedman

Extreme weather events will be a major source of future losses.

Construction worker Dineose Vargas wipes his face at a construction site on the Duncan Canal in Kenner, La., on Aug. 13. (Gerald Herbert/AP)

Extreme weather events, cuts to worker productivity and other effects of climate change could cause major global economic losses unless greenhouse gas emissions are significantly curtailed in the next few decades, according to a new working paper published Monday. The paper is the latest in a string of reports from the United Nations and global financial institutions and others showing that climate change constitutes a looming financial risk.

At a time when there’s concern about a global economic downturn, the new study, published as a working paper in the National Bureau of Economic Research, warns of a far bigger cut to economic growth if global warming goes unchecked.

The study is unique in that it finds higher potential costs from climate change, particularly in the industrial world, compared with past research. For example, the study found that continued temperature increases of about 0.072 degrees per year (0.04 Celsius) under a roughly “business as usual," or high-emissions, scenario would yield a 7.2 percent cut to GDP per capita worldwide by 2100. (This is relative to a world in which countries see temperature increases equal to their 1960 to 2014 rate of change.)

In contrast, if countries were to cut greenhouse gas emissions in line with the Paris climate agreement, then such effects could be limited to closer to a 1.1 percent loss in GDP per capita.

“What our study suggests is that climate change is costly for all countries under the business as usual scenario (no matter whether they are hot or cold, rich or poor), and the United States will be one of the countries that will suffer the most (reflecting sharp increases in U.S. average temperatures by 2100),” study co-author Kamiar Mohaddes, an economist at the University of Cambridge, said via email.

For the United States, the study finds that if emissions of greenhouse gases are not significantly cut in keeping with the goals of the Paris accord, the country could see a 10.5 percent cut in real income by 2100. The hardest hit countries will be poorer, tropical nations, but in contrast to previous studies, the new paper finds that no country will be spared and none will see a net benefit economically from global warming.

The team of researchers from the University of Cambridge, the International Monetary Fund, the University of Southern California and the National Tsing Hua University in Taiwan examined economic data from 174 countries during the period from 1964 to 2014, and concluded that per capita economic output growth is adversely affected by prolonged changes in temperature, both above or below its historical norms. Extreme temperature and precipitation events can reverberate throughout state, national and international economies, the study found.

“It is not only the level of temperature that affects economic activity, but also its persistent above-norm changes. For example, while the level of temperature in Canada is low, the country is warming up twice as fast as rest of the world and therefore is affected by climate change (including from damage to its physical infrastructure, coastal and northern communities, human health and wellness, ecosystems and fisheries),” Mohaddes said.

Other countries will experience major losses, too, if emissions of planet-warming greenhouse gases are not reduced soon. Canada, for example, could lose more than 13 percent of its GDP by 2100, while Japan, India and New Zealand could be subjected to a 10 percent hit as well.

Mohaddes said the study takes into account the changes in average temperatures and precipitation, and in the variability of weather patterns as the climate warms.

For the United States, the new study comes up with a similar damage figure as a paper cited in the National Climate Assessment, which the Trump administration released late last year. That report contained a statistic that received widespread media attention, finding that climate change could cost the country 10 percent of its GDP.

However, the previous figure was based on a 2017 paper in the journal Science, and used an extreme, although possible, climate change scenario, with about 14.4 degrees (8 Celsius) of warming by 2100 compared to preindustrial levels, which is not considered the most likely outcome.

The study released Monday comes to nearly the same figure using a more realistic global warming scenario, one that’s closer to 7.2 degrees (4 Celsius) of warming by 2100 compared to preindustrial levels.

Mohaddes says that economic losses from climate change depend in part on extreme events, which can cause temperatures to temporarily greatly exceed or fall below their historical baseline.

“The UK recently had its hottest day on record. Train tracks buckled, roads melted, and thousands were stranded because it was out of the norm. Such events take an economic toll, and will only become more frequent and severe without policies to address the threats of climate change,” Mohaddes said in a statement.

The study, like other projections on how climate change may influence economic growth, makes assumptions about emissions trends, how society may try to adapt to the effects of global warming and other factors. However, although the specific figures may contain uncertainties, the overarching finding that all countries will experience economic damage from climate change, rather than just poor, tropical nations, is more robust.

Links

• Increasing humidity, driven in part by climate change, is making even modest heat waves unbearable
• Long-Term Macroeconomic Effects of Climate Change: A Cross-Country Analysis
• Where the alarming economic damage stat in the new climate report came from
• Fighting climate change will help economic growth, study finds
• Climate change to shrink economies of rich, poor, hot and cold countries alike unless Paris Agreement holds
• Estimating economic damage from climate change in the United States