Those of you who remember the past winter's polar vortex with loathing will find some solace in the news that climate change will increase temperatures in autumn and winter. The onslaught of closed schools and immobilizing roads that gripped much of the U.S. and Europe will likely stay a thing of the past.
The warming temperatures in the Arctic may mean that the winds from the north that attack in winter will be warmer than before, and the variability in the temperatures will also decrease. Both autumns and winters will see less of a temperature chill.
There is, as usual, controversy surrounding these theories. Some climate scientists analyze the evidence and conclude that rapid Arctic warming actually restores cold winds that push storms like the polar vortexes through the Northern Hemisphere. James Screen, along with other scientists, believes instead that the Arctic warming did not account for the polar vortex, and that the change in Arctic climate will lead to less-variable temperatures in the U.S. and Europe.
"Those cold northerly winds are warming more rapidly than the warm southerly winds, which means you get fewer cold extremes," says Screen, a climate scientist at the University of Exeter. Screen used advanced mathematical climate modeling to show significant decreases in variability in autumn and winter temperatures, and published his findings in Nature Climate Change.
"Arctic amplification," Screen says, "decreases temperature variance in northern mid-to-high-latitudes." With his mathematical models he predicts the decreases in variance will persist in the future as a result of the Arctic warming. The rapid temperature increases in the Arctic outpace those anywhere else on the planet, leading to shrinkage of sea ice and melting of the snow cover. As the snow cover diminishes, the dark surfaces underneath absorb energy from the sun and speed the rate of warming even more. The fastest warming rates in the Arctic occur in the autumn and winter.
As for the frigid temperatures that graced our hemisphere last winter, Screen says it's just the weather. The polar vortex, he says, was not the direct result of changes in polar jet streams, which are fast currents of air that form in the boundaries between large temperature differences in the atmosphere.
"What happened in the past winter wasn't anywhere near as unprecedented or unusual as [it was] made out to be," Screen says. He added that only a small number of all-time record low temperatures were set.
Screen's findings still do not refute the hypothesized jet stream alteration leading to extreme weather patterns, but certainly adds dialogue to the climate change conversation.