Wednesday, March 15, 2017

Arctic Sea Ice Melt, Driven by Global Warming, Accelerated by Nature

A new study shows how much natural variability is boosting the rate of melting in the Arctic, which might be free of sea ice sooner than expected.

Arctic sea ice is melting at an accelerating rate as a new study pinpoints how much is from manmade global warming and how much from natural variations. (Credit: Getty Images) Click to Enlarge.
A new study zeroes in on just how much of the Arctic sea ice's precipitous decline in recent decades is attributable to man-made global warming and how much is due to natural processes, finding that between 50 and 70 percent is caused by mankind.

By studying air current patterns, researchers determined that between 30 and 50 percent of the decline in summer sea ice in the Arctic since 1979 may be due to natural processes, for the first time breaking down just how much melting could be attributed to each cause.  The study was published Monday in the journal Nature Climate Change.

"If we look to Earth as a whole, the global temperature rise is definitely due to anthropogenic forcing in the last 100 years.  There's no question of that," said author Qinghua Ding, a professor at the University of California Santa Barbara.  "But if we zoom in, some internal role comes in to have some impact."

Arctic sea ice has been rapidly declining since satellites first started tracking it in 1979, and according to NASA, roughly 13.3 percent of the ice disappears every decade.  Models have projected that man-made global warming would heat the Arctic faster than it would heat more temperate regions, and observation has borne that out.  The Arctic is warming at least twice as fast as the rest of the globe, and the first two months of this year both had the lowest levels of sea ice on historical record.

Though models have accurately predicted for decades that the ice would decline as the amount of carbon in the atmosphere increases, in recent years, the actual rate of melting has outpaced the models.

That's where Ding's study comes in.  What he and his coauthors found is that air currents that are a part of Earth's natural variability have played a significant role in melting the ice, which helps explain why the models have underestimated the melting.

Read more at Arctic Sea Ice Melt, Driven by Global Warming, Accelerated by Nature

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