By Brad Plumer
How much economic damage will global warming cause? That’s one of the key questions embedded in the Trump administration’s recent proposals to weaken Obama-era regulations on greenhouse gas emissions from both vehicles and power plants.
When federal agencies calculate the costs and benefits of climate regulations, they use a figure called the “social cost of carbon,” an estimate of the harm caused by releasing more carbon dioxide into the atmosphere and increasing global warming.
In its rollback proposals, the Trump administration argued that each ton of carbon dioxide emitted by a car or a coal plant in 2020 would only cause around $1 to $7 in economic damages. That’s far lower than the Obama administration’s central estimate, which, after adjusting for inflation, argued that same ton of carbon dioxide would cause roughly $50 in total damages.
That change will make a big difference for the cost-benefit analyses that agencies are required to conduct for new rules. If the Trump administration can successfully claim that carbon dioxide causes relatively little harm to the economy, then it can more easily justify moves like replacing the Clean Power Plan, an ambitious Obama-era program to cut pollution from coal plants, with a less-stringent rule.
The Trump administration may not be finished adjusting the social cost of carbon. In earlier proposals, the E.P.A. said “improved domestic estimates” could be developed in the future.
Most experts agree that the social cost of carbon can be improved by taking into account newer scientific and economic research. “There’s been an explosion of research on the impacts of climate change in recent years, and it hasn’t been fully reflected in the estimates,” said Michael Greenstone, an economist at the University of Chicago who helped craft the Obama administration’s original numbers.
Dr. Greenstone was an author of a recent paper that looked more carefully at projected heat deaths from global warming as well as the costs of adapting to higher temperatures, such as buying more air-conditioners. That study concluded that these costs alone could add an extra $18 or more to the social cost of carbon.