Over the last week of 2017 and first week of 2018, a cold wave gripped the northeastern U.S. and southeastern Canada, with temperatures over 18ºF (10ºC) colder than is typical at this time of year over this area, setting records at many sites.
Severe winter weather struck southeastern Europe, with extreme cold and snow in Italy, the Balkans and Turkey. This caused many accidents on roads, school closures, and cancelled flights. The Danube river and Bosporus sea strait were closed for shipping.
How rare were the unusually high temperatures around the North Pole in November–December 2016 and how were they influenced by anthropogenic climate change?
Speculation about the cause of forecast record low temperatures in the US led WWA researchers to explore the cold air outbreak – how was it affected by greenhouse gas emissions?