A highly granular assessment of the impacts of climate change on the U.S. economy suggests that each 1°Celsius increase in temperature will cost 1.2% of the country's gross domestic product, on average. Different from past analyses of climate change in the U.S., which suggested the country would benefit or lose as a single entity, this study captures regional differences: locations in the south, for example, are at much higher risk of incurring economic damage, while areas in the Pacific Northwest and New England may experience a slight economic gain. Because losses are expected to be largest in regions that are already poorer, on average, climate change will tend to increase preexisting inequality in the United States, the authors say. Estimates of climate change damage are central to the design of climate policies. To better quantify the costs of climate change in the U.S., and at higher-resolution than in past, Solomon Hsiang and colleagues developed a model that integrated data capturing the effects of short-term weather fluctuations between 1981 and 2010 on six key economic factors, such as agriculture yield and labor supply. They used these data to construct estimates of future economic impacts based on climate change projections under a "business-as-usual" approach (one in which fossil fuels continue to be used intensively). Unsurprisingly, Atlantic coast counties are expected to suffer the largest losses from cyclone intensification and sea level rise, they report. Overall though, southern and midwestern populations are projected to suffer the largest losses, exceeding 20% of gross county product (GCP) in some instances, while some northern and western populations may actually see small economic gains - up to 10% of GCP. The model estimates that average yields in agriculture will decline by about 9%. As well, mortality rates will increase by about 5.4 deaths per 100,000, for each 1°C increase. In a related video interview, Hsiang highlights some of the policy-oriented implications of this work: "We've shown which U.S. regional economies are particularly vulnerable, which will help policymakers... If we are going to adapt, we need to know where to focus."
These results are highlighted in a Perspective by William A. Pizer. Reporters can find the economic damages projected for their county by visiting this site http://globalpolicy.science/econ-damage-climate-change-usa and using the password "embargoed17."