Updated Jun 23, 2018 - Energy & Environment

Where climate change will hit the U.S. hardest

Left unmitigated, rising temperatures from climate change will increase inequality and mortality rates in the U.S. by the end of the 21st century, a team of economists and climate scientists warn in a study published today. It's the first to project the impacts of climate change on individual counties in the U.S. Many of those predicted to be hit hardest are in fast-growing Arizona, Texas, and Florida.

Data: Hsiang, Kopp, Jina, Rising, et al. (2017); Map: Lazaro Gamio/Axios

Local differences: If steps are not taken to lessen the rate of warming from climate change, counties in the South and lower Midwest — which on average tend to already be poorer and warmer — may lose as much as 20% of their income and may experience higher mortality rates. However, areas of the Pacific Northwest, the Great Lakes region and New England — which on average tend to be wealthier and cooler — could benefit economically from the change and see lower mortality rates.

A climate impact map by county is available here.

"The poorest 10% of counties stand to lose over 10% of their county GDP, while many richer counties will see climate-driven boosts." — study author James Rising of UC Berkeley.

Dire warning: The researchers predict mortality will increase by 5.4 deaths per 100,000 people for every one degree Celsius rise in temperature. "We show there are going to be as many additional deaths from climate change as there are car crashes, and possibly more. Of the sectors we looked at, the greatest costs by far to society are going to come from those additional deaths," Rising told Axios. But it would vary by region: in cold northern counties, warming reduces mortality whereas in southern ones it could rise.

Nationwide, for every one degree Celsius temperature rise, the study predicts:

  • Gross domestic product will drop 1.2%
  • Agriculture average yields will decline by 9%
  • Electricity demand will rise by 5.3%
  • Total hours of labor supplied will drop — by 0.11% for low-risk workers (work mostly indoors) and 0.53% for high-risk workers (exposed to outdoor temperatures).
  • Violent crime will rise by roughly 0.88% nationally. Property crime (which tends to be lower in cold weather) will increase with warming but doesn't change once it reaches hot levels of temperature.
  • Coastal damage will be distributed unequally: acute impacts could be felt in eastern coastal states with low-lying cities. The rise of Middle Sea Levels alone raises expected economic damage to South Carolina, Louisiana, and Florida in particular.

Outside perspective: One of the study authors said that unmitigated climate change may result in the largest transfer of wealth from the poor to the rich in U.S. history. In response, Stanford University's Marshall Burke told Axios:

"Poor counties in the U.S. will be harder hit, mainly because they are already hot. Whether we should think of climate change as a "transfer" of wealth is less clear to me, though, and it is also less clear that even if we want to use "transfer" in the way they are using it, that this would be the biggest transfer in U.S. history. For instance, I think it's correct that the differential growth in incomes between the poorest 20% of U.S. household and the richest 1% has been a lot bigger over the last 20 years than the effects they find here."

What they did: The team used historical records of temperature effects on different sectors and 116 climate projections to price the real-world costs of higher temperatures, changing rainfall, rising seas, and intensifying hurricanes to 6 key economic factors: agriculture yield, crime rates, health, energy demand, labor supply, and coastal damage. The projections across all U.S. counties and a range of possible future climates are for four blocks of time between 2020 and the end of the 21st century that are compared to historical data from the period from 1989 to 2001.

"For the longest time when we talked about climate change it has been at the global level. One of the challenges is that it is hard to translate global stats to a local level," says UC Santa Barbara's Kyle Meng. "What's important about this work is that it put a lot of effort into summarizing the literature so we are able to actually tell what impacts will look like at particular locations in the U.S."

Limitations: The study doesn't account for technological adaptations that might mitigate the effects or the impact of migration on the population.

Added value: The team developed the Spatial Empirical Adaptive Global- to-Local Assessment System (SEAGLAS), which will be able to take in research across multiple fields and analyze in near-real time. "They've created a platform that researchers can update continuously so we can get real-time updates of our understanding of climate change, not just discrete ones every time a study is published," says Meng, who has collaborated with the team in the past but wasn't involved in the current study.

What's missing: "The main worry that I have — and this is clearly mentioned in the paper — is that they are missing some important sectors because impact estimates do not exist for these sectors. Morbidity in particular is probably the most important one, and this could mean they are substantially understating overall impacts," Burke added.

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