National Academies Report Measures Possible Climate Change Impacts

On July 16, the National Academy of Sciences released a report titled Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millenia which estimates changes in precipitation, streamflow, wildfires, crop yields, and sea level rise that can be expected with increased average global temperature. The report pulled together a vast amount of scientific data to offer likely ranges and best estimates of the equilibrium warming that can be expected from various levels of carbon dioxide in the atmosphere.

Some impacts included a 5 to 15 percent drop in yields of some crops, including U.S. and African corn and Indian wheat, for every 1°C of warming; a 5 to 10 percent drop in total rain in southwest North America, the Mediterranean, and southern Africa for every 1°C of warming; and a 5 to 10 percent decline in streamflow in some river basins, including the Arkansas and Rio Grande, for every 1°C of warming.

The study was undertaken to help policymakers understand the potential impacts associated with emission cuts that may result from policies currently under consideration. “Many of us have had the experience of going to the doctor and receiving advice on how to improve our health,” said Katharine Hayhoe , a scientist from Texas Tech University who contributed to the report. “Then, it’s up to us to decide how much we are willing to change. In a similar way, this report presents the probabilities of certain impacts at different levels of global temperature increase. But we, the scientists, can’t make the decisions of how much risk is acceptable. That’s a political decision. Rather, we’re trying to give policymakers the information they need to make these decisions.”