Thomas Mote and Emily Kutney of the University of Georgia compared Eurasian snow cover with winter temperatures across North America between 1967–68 and 2007–08. The results showed that the amount of autumn snow cover in a band that runs from northern Scandinavia to the West Siberian Plain is significantly associated with winter temperatures over the interior of North America. The greater the snow cover, the lower the winter temperatures in the central USA in January, extending to the eastern and southern USA in February. The difference could be as great as 5°C.

The findings should improve seasonal climate outlooks, which predict whether upcoming seasons will be colder or warmer, or wetter or drier than normal. Years with extensive autumn snow in northwest Eurasia were associated with subsequent winter temperatures that were as much as 4°C lower near the centre of North America. This difference is roughly the same as a one-month shift in climate.

Previous studies have suggested a link between Eurasian snow cover and winter temperatures in North America, but this is the first to narrow down the location of the area that has the most direct effect. ‘One difficulty in comparing previous studies is that they have used multiple definitions of Eurasian snow cover,’ said Mote. ‘Our work looked at the role of various key areas of Eurasian snow cover on atmospheric circulation, including the systems called the Arctic Oscillation and the Pacific/North American teleconnection.’

August 2011