Climate change will wreak havoc on the U.S. economy, leading to as much as a 3% decline in national GDP by the end of the 21st century if left unaddressed — and losses will be far higher in some of the country's poorest areas, according to a new study.
Researchers behind the study, published in the journal Science, evaluated a number of factors that will contribute to economic decline as average global temperatures continue to rise, including increased energy costs, coastal damage, mortality rates and damage to agriculture. The study authors did not assess some other factors that carry economic costs, like damage to biodiversity, because such losses can be difficult to quantify.
The southern U.S. and mid-Atlantic region will face the worst losses, while some places in the North may actually benefit from higher temperatures, according to the study. In the places where climate change hits hardest — think the entire South from Texas to Florida — the economic losses could be nothing short of devastating. In many locations, GDP decline could total more than 10%, and in the worst-hit county, Florida's Union County, losses could near 28%.
Predicting the exact consequences of such a climate-fueled recession is impossible, but researchers say the geographic disparities would contribute to political instability and could drive mass migration, with effects felt across the country. "If we continue to emit, you go into this recession and you get stuck in it forever," says study author Solomon Hsiang, an associate professor of public policy at the University of California, Berkeley. "Conflict and political instability — those kinds of things we don't see today, but could be baked into the future."
The study assumes greenhouse emissions continue on their current trajectory, with average global temperatures rising between 2.6°C (4.7°F) and 4.8°C (8.6°F) by the turn of the century. Nearly every country agreed to work to keep temperatures from rising to those levels in the 2015 Paris Agreement. But the document's target of keeping temperature rise below 2°C (3.6°F) was a long shot when countries brokered the deal in 2015, and it faces further uncertainty following President Trump's decision to withdraw.
The research comes as the Trump administration seeks to undo policies aimed at addressing climate change, arguing that they harm the economy. Some climate change rules and regulations may restrict economic growth in certain areas. But, as the new research shows, leaving the issue unaddressed carries serious risks and costs — something Trump has shown less interest in addressing.
The Trump administration has changed the way the federal government considers the cost of climate change — known as the social cost of carbon— in cost-benefit analysis. The decision gives agencies more leeway to give more weight to immediate economic benefits of some decisions, while giving less weight to the long-term economic disruption caused by climate change. Beyond that, Trump has begun the process of undoing Obama-era climate regulations and sought to defund research that will foster renewable energy growth.
Despite Trump's position on climate change, some have suggested that research on global warming's costs could sway some in the administration. "The pendulum for environmental protection can swing back and forth," writes Duke University public policy professor William A. Pizer in an editorial accompanying the study. "Yet conservative governments, including the current one, have maintained an emphasis on [cost-benefit analysis]."
The study only evaluates the economic impact of climate change in the U.S., and the study authors acknowledge that the worst effects of climate change will likely occur outside the country. Those impacts could also affect the U.S., drawing the country into foreign conflicts and increasing global instability. The U.S. military has called climate change a "threat multiplier" and connected it to mass migration and instability. That instability may originate outside U.S. borders, but the effects will resonate domestically, even if we do not know how significantly.