Warming effect in a world without snow


Losing every last snowflake in the world is an unlikely scenario. But global warming is expected to melt around 10-20% of the world's snow in the future and, by modelling the no-snow climate, Stephen Vavrus from the University of Wisconsin-Madison was able to work out how the predicted melting would affect the planet.

Snow tends to cool the air above it and stops the Earth from overheating. Professor Vavrus found that, in a world without snow, the temperatures in the northern hemisphere rocketed. "Without snow we see a large atmospheric warming of up to 5C over northern Eurasia and North America annually (8-9C in winter), and a globally averaged warming of 0.8C," he said.

However, snow also provides a warm insulating blanket and without it vast areas of land would become permanently frozen. "Soils in presently snow-covered areas, such as Siberia, would cool considerably, by up to 20C during winter. As a result, the permafrost would expand equatorwards by 500 to 1,000 kilometres [up to 600 miles], even though the overlying air warms by several degrees," said Prof Vavrus, who will present his findings at the autumn meeting of the American Geophysical Union in San Francisco this week.

One of the main reasons for the increase in temperature is that the snow would no longer be cooling the air over the Arctic. Northerly winds would lose their edge and winter cold snaps would become a thing of the past. Soils would also become drier, making life more difficult for plants.

Prof Vavrus said: "If the warming trend coincides as expected with reduced snow cover, then this simulation shows that a tug-of-war may ensue, such that the loss of snow cover favours an expansion of permafrost while the warmer atmosphere favours a contraction of permafrost area."