The U.S. urgently needs to trim its greenhouse gas emissions, a report from the National Research Council says. It suggests that policymakers limit the nation’s emissions to between 170 billion and 200 billion tons of CO2 from 2012 to 2050, averaging 4 billion to 5 billion tons per year. In comparison, the U.S. now releases about 7 billion tons annually, says Robert W. Fri, who chaired the NRC panel that compiled the report, “Limiting the Magnitude of Future Climate Change.” The report is one of three that were mandated by Congress and released by NRC last week. A second report, on climate science, affirms that climate change is being detected and is primarily because of human activities, notably the burning of fossil fuels. Among its recommendations is research on solar radiation management, a form of geoengineering. The third report focuses on adaptation to unavoidable climate-change effects, such as rising sea levels. It warns that resources can no longer be managed according to previous experience and the historic variability of climate. Two more NRC reports in the series, one focused on providing information for effective decisions on climate change and the other offering a scientific framework for shaping policy choices, will be released later this year.