Extreme Weather: Record-breaking Cold Winter of 2009/10 in the Northern Hemisphere
Wang, C., Liu, H. and Lee, S.-K. 2010. The record-breaking cold temperatures during the winter of 2009/2010 in the Northern Hemisphere. Atmospheric Science letters 11: 161-168.
Cattiaux, J., Vautard, R., Cassou, C., Yiou, P., Masson-Delmotte, V. and Codron, F. 2010. Winter 2010 in Europe; A cold extreme in a warming climate. Geophysical Research Letters 37: L20704 doi:10.1029/2010GL044613.
Cattiaux et al. made a similar analysis of the NAO index and showed how the extreme persistence of daily NAO values led to the development of North Atlantic atmosphere blocking, which lead to the cold-air outbreak and severely cold winter over Europe. Cattiaux et al. further analyzed the severity of the winter of 2009/10 over Europe and concluded that it was comparable to the cold winter of 1963. They further state that the winter of 2010 "can be considered as an example of a cold extreme superimposed on a warming climate (of Europe)."
So what does the future hold? Wang et al. conclude that similar cold winters are likely to recur, while Cattiaux et al. suggest that future winters over Europe may not be as cold as experienced in 2009/10. Another paper (Kodra et al., 2011) suggests that "cold extremes are expected to decline in frequency by the end of 2100, but there will still be cold weather extremes which could be as intense or even more intense than present cold weather extremes." In view of these contrasting conclusions, the jury is still out!
Kodra, E., Steinhaeuser, K. and Ganguly, A.R. 2011. Persisting cold extremes under 21st century warming scenarios. Geophysical Research Letters 38: doi:10.1029/2011GL047103.