The Arctic will begin warming by 1ºF (0.55ºC) per decade by the 2020s, a rate of change that has not been seen in at least 1,000 years, according to a new modelling study by the U.S. Pacific Northwest National Laboratory (PNNL).
In PNNL’s best-case scenario, the world-wide warming trend hits 0.45ºF (0.25ºC) per decade over four decades, and atmospheric carbon dioxide stabilizes at 525 parts per million, far above the limits that would avert runaway climate change. Northern latitudes would warm twice as fast, so the Arctic would reach and quickly surpass a warming rate of 1ºF per decade.
“Such rapid Arctic warming would be ominous for several reasons,” writes Joe Romm, founding editor of the Climate Progress blog. “First, it would likely speed up the already staggering rate of loss of Arctic sea ice. Second, if, as considerable recent research suggests, Arctic amplification has already contributed to the recent jump in extreme weather, the next few decades are going to be utterly off the charts.”
By accelerating the loss of the Greenland ice sheet, rapid warming would also increase sea level rise below the six feet already projected for this century. And “such rapid warming would serve to accelerate the release of vast amounts of carbon from defrosting permafrost,” an outcome that would increase warming by an estimated 1.5ºF this century.
“In these climate model simulations, the world is just now starting to enter into a new place, where rates of temperature change are consistently larger than historical values over 40-year time spans,” said lead author Dr. Steve Smith. “We need to better understand what the effects of this will be and how to prepare for them.”