Arctic Getting "Wetter" Due to Human-Driven Warming

April 25, 2008

In addition to heating up faster than almost anywhere else on the planet, the Arctic has gotten wetter and snowier because of global warming, according to a new study.

The extra precipitation could freshen ocean water in the Arctic and North Atlantic, researchers say, which might disrupt the so-called ocean conveyor belt, a current that runs through the Atlantic and carries warm water northward from the Equator.

The new study is the first to show that changes in precipitation in the Arctic are in part human-induced, said study leader Francis Zwiers of the government agency Environment Canada.

The study also shows that previous computer models underestimated how much precipitation would change because of global warming.

Contrary to the simulations, Arctic rain and snowfall increased by 7 percent over the past 50 years, the study found. In just the Canadian Arctic, precipitation jumped 11 percent.

"That might not seem very big, but a 10 percent change is quite a lot" when it comes to precipitation, Zwiers said.

The discrepancy means that models predicting future change "may underestimate what's coming down the pipeline," he said.

"If people are using these models for planning, they should keep in mind that what the models show may be weaker than what will happen."

Turning On and Off

For their work, Zwiers and colleagues considered whether changes in precipitation are due to human activities or are being caused by natural events such as volcanic eruptions or changes in the sun.

The team also tested whether natural, chaotic variability in climate could be to blame.

Using computer models, the researchers could turn each of these forces on and off to see which contributed the most to the changes that have been observed.

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