Joe Romm sends us to: NASA’s James Hansen, Reto Ruedy, Makiko Sato and Ken Lo, “2010 — Global Temperature and Europe’s Frigid Air”:
This is the warmest January-November in the GISS analysis, which covers 131 years. However, it is only a few hundredths of a degree warmer than 2005, so it is possible that the final GISS results for the full year will find 2010 and 2005 to have the same temperature within the margin of error.... November 2010 surface temperature anomalies based only on surface air measurements at meteorological stations and Antarctic research stations... to allow extreme temperature anomalies to be apparent. Northern Europe had negative anomalies of more than 4°C, while the Hudson Bay region of Canada had monthly mean anomalies greater than +10°C. The extreme warmth in Northeast Canada is undoubtedly related to the fact that Hudson Bay was practically ice free. In the past, including the GISS base period 1951-1980, Hudson Bay was largely ice-covered in November.... Sea ice insulates the atmosphere from ocean water warmth, allowing surface air to achieve temperatures much lower than that of the ocean. It is for this reason that some of the largest positive temperature anomalies on the planet occur in the Arctic Ocean as sea ice area has decreased in recent years.
The cold anomaly in Northern Europe in November has continued and strengthened in the first half of December.... [I]s it possible that reduced Arctic sea ice is affecting weather patterns?... The fixed location of the Hudson-Baffin heat source could plausibly affect weather patterns, in a deterministic way — Europe being half a Rossby wavelength downstream, thus producing a cold European anomaly in the trans-Atlantic seesaw. Several ideas about possible effects of the loss of Arctic sea ice on weather patterns are discussed in papers referenced by Overland, Wang and Walsh. However... the few years just prior to 2009-2010, with low Arctic sea ice, did not produce cold winters in Europe. The cold winter of 2009-2010 was associated with the most extreme Arctic Oscillation in the period of record.... 7 of the last 10 European winters were warmer than the 1951-1980 average winter, and 10 of the past 10 summers were warmer than climatology. The average warming of European winters is at least as large as the average warming of summers, but it is less noticeable because of the much greater variability in winter.