Are the Two Most Recent Harsh Northern Hemisphere Winters Manifestation of Anthropogenic Global Warming in the Arctic?

Author: Judah Cohen and Jason C. Furtado
Date: 
December 7, 2011
Type: 
Poster presentation
Venue: 
AGU Fall Meeting 2011
Citation: 

Judah L. Cohen, Jason C. Furtado, M.A. Barlow, V.A. Alexeev, J.E. Cherry (2011) Are the Two Most Recent Harsh Northern Hemisphere Winters Manifestation of Anthropogenic Global Warming in the Arctic?. AGU Fall Meeting, 2011

The global climate models predict that temperatures will warm the greatest in winter due to a positive feedback of increased greenhouse gases (GHGs) and a diminished and darker cryosphere. However, headlines on the two most recent years have been less about the extreme warmth and more about the severity of winter weather and record snowfalls. What dynamic forcings could contribute to reversing the radiative warming forced by both increased GHGs and decreased planetary albedo resultant of a shrinking cryopshere? Furthermore, current consensus on global climate change predicts warming trends over the NH continents during boreal winter. However, recent trends in Northern Hemisphere (NH) seasonal surface temperatures diverge from these projections. For the last two decades, NH landmasses have experienced significant warming trends for all seasons except winter, when large-scale cooling trends exist instead. The surface temperature trend pattern is most closely associated with the negative polarity of the Northern Annular Mode (NAM), which has been linked with leading stratospheric circulation anomalies. These circulation anomalies are, in turn, linked with increasing Eurasian snow cover in the fall; an observed increasing trend in Eurasian snow cover, in part forced by a warming Arctic is the most likely boundary condition for partially forcing winter hemispheric trends over the past two decades that has heretofore been identified. We will also compare the trend analysis with the NAM to trend analysis with varying sea surface temperatures associated with El Nino/Southern Oscillation, the Pacific Decadal Oscillation, the Atlantic Multidecadal Oscillation, solar variability and diminishing Arctic sea ice.