Geosciences: Feeling the Heat

By now, the scientific community overwhelmingly agrees that Earth is warming — climate models predict a national rise in temperature in the U.S. of between 2 and 7 degrees Celsius over the next 100 years. What’s harder to gauge is how that rise will affect citizens in their own backyards. “No one lives at the national level — people live at the local level,” says Bob Kopp, a climate scientist at Rutgers University-New Brunswick who is a former Princeton postdoc. “If you look at the impacts at too aggregated a scale, you miss a lot of the story.”

COUNTY-LEVEL ANNUAL DAMAGE: 2080–99 Median county-level annual impact of climate change for 2080–99 under a business-as-usual emissions trajectory. Top row, left to right: percent change averaged for maize, wheat, soybeans, and cotton; changes in all-cause mortality rates, across all age groups; middle row, left to right: change in electricity demand; change in damage from coastal storms and sea-level rise: bottom row, left to right: changes in violent-crime rates; median direct economic damage.

Hsiang, Kipp, Jina, Rising, et al. (2017)

Kopp is part of a research team — including Princeton geosciences and public policy professor Michael Oppenheimer, Woodrow Wilson School doctoral student DJ Rasmussen, and University of California, Berkeley professor and former Princeton postdoc Solomon Hsiang — that has developed a prognosis of how climate change is likely to affect the country on a local level. In a paper published in Science in June, they and their eight additional collaborators found a huge discrepancy in the effects of climate change on economic activity depending on where people live.

They examined impacts such as heat- and cold-related deaths, the ability of people to work in the heat, crop yields, energy demand, coastal storms, and crime. While some areas, including the far North and parts of the Rockies, might not experience much net harm — or may even benefit from modestly higher temperatures — areas in the South are especially at risk.

As a result, economic inequality between regions will worsen. “Places that are already warm will be harmed much more than places that are cooler,” Kopp says. “Those warmer places also coincidentally tend to be places that are already poorer, so the net effect will be a transfer of wealth from South to North and from the poorer to the wealthier.”

The paper takes advantage of econometric research that has emerged in the last decade to create detailed information on the effects of weather patterns on economic activity. “In the past decade, there has been an explosion of research that has allowed us to leverage new sources of information,” says Rasmussen, who analyzed much of the climate data. By using cloud computing capable of handling vast quantities of data, the researchers crunched the numbers on a county-by-county basis across the country to drill down to localized effects.

Some areas, such as northern Michigan and Maine, could experience the equivalent of more than a 10 percent increase in gross domestic product (GDP), due to fewer deaths from cold weather, lower energy costs, and longer growing seasons. Areas in the southeastern states, meanwhile, could see equivalent losses of 25 percent of GDP or more. Those losses are almost entirely driven by increases in temperature, the researchers found. Despite fallout from high-profile weather events such as Hurricanes Harvey and Irma, those hardships pale in comparison to the effects of excess heat at a national scale. “The silent killer is the increase in temperature,” Rasmussen says, explaining that hotter temperatures will cause crops to wither, violent crime to increase, and people to die from heat exposure.

One thing the study doesn’t measure, however, is how people will respond to such changes in the climate — whether they’ll move from region to region, for example, or find other new ways to adapt. While ultimately the best way to mitigate these economic effects is to reduce greenhouse gases that cause climate change, the authors hope that the county-by-county data in the report will help local policymakers take preventative measures to adapt.

Decision-makers in coastal communities such as Miami, for example, could enact building codes that adapt to storm surges by providing incentives to build in different places, or elevating buildings, or adding protective structures. In other cases, communities could change the crop mix or add irrigation to combat decreases in crop yields, or install community cooling centers to stave off health effects of heat waves. “It’s no longer enough to just look at the past to decide on changes for the future,” says Rasmussen. “Our hope is that this information will give people what they need to think about what is coming down the road, and make changes now that will lower the economic cost of climate change.”

For a county-by-county projection of how local economies will be affected, go to http://bit.ly/climatedamage