Arctic warming, increasing snow cover and widespread boreal winter cooling

Abstract

The most up to date consensus from global climate models predicts warming in the Northern Hemisphere (NH) high latitudes to middle latitudes during boreal winter. However, recent trends in observed NH winter surface temperatures diverge from these projections. For the last two decades, large-scale cooling trends have existed instead across large stretches of eastern North America and northern Eurasia. We argue that this unforeseen trend is probably not due to internal variability alone. Instead, evidence suggests that summer and autumn warming trends are concurrent with increases in high-latitude moisture and an increase in Eurasian snow cover, which dynamically induces large-scale wintertime cooling. Understanding this counterintuitive response to radiative warming of the climate system has the potential for improving climate predictions at seasonal and longer timescales.

Attribution of divergent northern vegetation growth responses to lengthening non-frozen seasons using satellite optical-NIR and microwave remote sensing

“…In fall, the decreasing NF days' trend coincides with a positive trend in the number of TR days, implying that the fall TR season is beginning earlier and extending over a longer period. The seasonal decrease in NF days and the corresponding increase in TR days imply regional cooling in the fall; the mechanisms for this apparent HNL cooling are uncertain but are consistent with reported increases in HNL moisture and snow cover in fall attributed to summer warming and sea ice decline (Cohen et al 2012a(Cohen et al , 2012bPark et al 2013). The recent increase in fall snow cover may promote regional cooling due to an enhanced snow-albedo feedback (Déry and Brown 2007).…”

Attribution of spring snow water equivalent (SWE) changes over the northern hemisphere to anthropogenic effects

“…3c). Peng et al (2010) and Cohen et al (Cohen et al 2012(Cohen et al , 2014. Observed SWE for the hemispherical to the sub-continental scale regions shows overall decreasing trends for the 1980-2012 period, except for the regions 'EE' and 'EES' (Fig.…”

Spring onset variations and trends in the continental United States: past and regional assessment using temperature-based indices

“…Using a coupled global climate model (GCM), the study further documents that the pattern of Pacific decadal variability responsible for the warming hole in North America may be internally generated, and therefore not directly linked to climate change (Meehl et al, 2012). Alternatively, Cohen et al (2012)) suggest that the cooling trends in the eastern United States and northern Eurasia over the last few decades may belie dynamical interactions between greater Eurasian snow cover extent in the fall and negative winter AO. In other parts of the NH, including the leeside of the Tibetan Plateau, complicated interactions across seasons may explain delayed springs (Li et al, 2005).…”