The role of climate change in our weird winter weather …
Temperatures climbed above freezing again this week throughout Alaska. It’s the latest of several warm spells that’ve kept temperatures unseasonably high in this part of the Arctic this winter. And it raises the question whether climate change is a factor.
“No weather event is completely independent of climate change,” says University of Alaska-Fairbanks research professor John Walsh.
Climate change doesn’t cause every weather event in the Arctic or elsewhere around the world, Walsh said. But, he adds, it intensifies those events, such as the big snowstorm that hit the East Coast last week.
“We probably would have had a snowstorm without climate change,” he said. “But it probably wouldn’t have been so severe.”
Walsh, the chief scientist with the university’s International Arctic Research Center, says climate scientists have developed a metric to estimate how much global warming contributes to a weather event.
He says they’re now applying that metric, called fraction of attributable risk, or FAR, to determine the role climate change played in the formation of a large warm air mass that swept up and over the North Pole on New Year’s Eve, raising the temperature there to above freezing.
“... Even without climate change, there would have been a strong storm in the North Atlantic that pumped a lot of warm air up over the Arctic Ocean,” he said. “But that air probably wouldn’t have been as warm in the past.”
Rick Thoman is the resident climate-change expert at the National Weather Service’s office in Fairbanks. And he says meteorologists have been careful to attribute climate-change influence to weather phenomena, because the science is still relatively new and evolving. But, he adds, it’s clear forecasters need new calculating tools to replace those becoming obsolete in a warming world. Especially in the far north, where the impact of climate change has been so dramatic.
“In places like the coastal (Alaskan) North Slope, where in parts of the year, the climate has changed so dramatically in the last decade, those historically based tools simply don’t work anymore,” Thoman said.
Walsh says researchers using FAR generally find that climate change boosts the intensity of weather events by 10 to 20 percent. He says they’re now using the metric to estimate how much it has intensified El Nino and the North Pacific warm surface water phenomenon known as The Blob.
Walsh expects climate scientists will conclude climate change probably has significantly contributed to the intensity of El Nino. He says it’ll probably also be shown to have contributed to torrential rains that’ve soaked the western United States and heavy snowfall to the eastern U.S. He says that’s consistent with models that show climate change generally will promote heavier precipitation in lower and mid-latitudes, and warmer-than-usual temperatures at higher latitudes.
Editor's note: This story has been edited and updated for publication online.