Northern Hemisphere Cold Surges Result of Arctic and Tropical Pacific Synergistic Effects

China is just one of many countries in the Northern Hemisphere having what researchers are calling an “extremely cold winter,” due in part to both the tropical Pacific and the Arctic, according to an analysis of temperatures from Dec. 1, 2020, to mid-January of 2021. A country-specific case study, the investigation potentially has far-reaching implications for predictions and early warnings to protect against harmful impacts, researchers said.

The results were published online, ahead of print, on Feb. 12 in Advances in Atmospheric Sciences.

"We are trying to explain why the countries in the Northern Hemisphere more frequently encounter the extremely cold events against a global warming background, and we chose the 2020-21 extremely cold winter in China as a case study," said co-first author Prof. ZHENG Fei, International Center for Climate and Environment Science (ICCES), the Institute of Atmospheric Physics (IAP) at the Chinese Academy of Sciences (CAS).

Since Dec. 1, 2020, the lowest temperatures in 58 cities, including Shanghai and Beijing, either broke or set records. On average, temperatures are at least one to two degrees Celsius below normal across the country, with some areas reporting temperatures as much as four degrees Celsius below average.

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