There had been speculation that record low temperatures would be coming to the United States in early December, and this had been framed as either evidence against global warming in general or that cold air outbreaks are increasing due to climate change.

World Weather Attribution (WWA) presents a quantitative study of this cold air outbreak. WWA researchers compute how rare the outbreak was and how it is affected by human-caused greenhouse gases. The analysis uses the same methods as WWA used in the peer-reviewed analysis of the cold extremes in the Midwest in the winter of 2013 – 2014 (van Oldenborgh et al, 2015). Continue reading U.S. Deep Freeze, December 2016 →