Warmer Summers Causing Colder Winters in Northern Hemisphere, Study Suggests
16.01.2012 - Atmosphere & Space, Ice & Snow, Arctic
According to research recently published in Environmental Research Letters, increasingly warmer summers can lead to colder winters in certain locations in the Northern Hemisphere. The strongest winter cooling trends have been observed in southern Canada, the eastern United States, and northern Eurasia. Researchers from the University of Massachusetts and the University of Alaska Fairbanks believe these cannot be entirely explained by natural climate variability.
Researchers have found that increasing temperatures and melting ice in the Arctic are creating greater snowfall in the autumn months in the lower latitudes.
Strong warming from July to September in the Arctic, which continues through the autumn appear to enhance the melting of sea ice. A warmer atmosphere along with melting sea ice creates conditions that allow the atmosphere in the Arctic to hold more moisture, which increases the likelihood of precipitation over lower latitudes. In freezing temperatures this precipitation falls as snow.
Increased snow cover in the mid-latitudes also has an effect on the Arctic Oscillation, causing it to remain in a negative phase. When the Arctic Oscillation is in its negative phase, it pushes cold, Arctic air into the mid-latitudes.
As global temperatures increase, this will favour warmer temperatures “in all seasons and in all locations”, according to Judah Cohen from the University of Massachusetts, lead author of the study. However if warming continues, precipitation that falls as snow in winter will eventually fall as rain, and regional cooling in winter will no longer take place.