New Scientific Evidence Builds a Stronger Case for the Endangerment Finding: In the years since the US Environmental Protection Agency's 2009 (EPA) establishment of the "Endangerment Finding," a landmark redefinition of harmful greenhouse gasses to pollution, scientific information concerning the impacts and risks of climate change has continued to accumulate. In a Review, Phillip Duffy and colleagues provide a comprehensive assessment of this growing body of scientific evidence which greatly supports and strengthens the Endangerment Finding's conclusion that these gases pose a threat to the public's health and well-being. According to the authors, the scientific case for endangerment, which was already overwhelming at its inception, is far stronger now. The Endangerment Finding (EF) established several greenhouse gases, such as carbon dioxide and methane, as air pollutants, and as such, are open to EPA regulation under the Clean Air Act. Duffy et al. highlight new scientific evidence covering the spectrum of observed and projected climate change impacts and their effect on public welfare, including those not yet known when the original EF was drafted, like ocean acidification, social instability and threats to national security. According to the authors, much of the new evidence indicates that some impacts have the potential to be more severe or more widespread than anticipated in 2009. This is particularly true for climate change-induced extreme weather events, many of which have had a tremendous impact on human health and security, agriculture, infrastructure and ecosystems. In addition, the authors note that some impacts -- or combinations of impacts -- could contribute substantial risk in ways not considered in the EF.