The National Research Council of the National Academies released a report on May 12 that provides another addition to the scientific consensus on the reality of climate change and its significant threats. According to scientists and public policy experts who prepared the report: “Climate change is occurring, is very likely caused primarily by the emission of greenhouse gases from human activities and poses significant risks for a range of human and natural systems.” The authors added, “The environmental, economic and humanitarian risks posed by climate change indicate a pressing need for substantial action to limit the magnitude of climate change and to prepare for adapting to its impacts.” N.R.C. researchers acknowledged that there is uncertainty about the scale and severity of future risk, but argued, “Uncertainty is not a reason for inaction, however; it is, in fact, a compelling reason for action, especially given the possibilities of abrupt, unanticipated and severe impacts.”