Arctic warming occurring faster than described, analysis shows

NEW YORK • The rapid warming of the Arctic, a definitive sign of climate change, is occurring even faster than previously described, researchers in Finland said on Thursday.

Over the past four decades, the region has been heating up four times faster than the global average, not the two to three times that has commonly been reported.

And some parts of the region, notably the Barents Sea north of Norway and Russia, are warming up to seven times faster, they said.

One result of rapid Arctic warming is faster melting of the Greenland ice sheet, which adds to rising sea levels. But the impacts extend far beyond the Arctic, reaching down to influence weather such as extreme rainfall and heatwaves in North America and elsewhere.

By altering the temperature difference between the North Pole and the equator, the warming Arctic appears to have affected storm tracks and wind speed in North America.

Dr Manvendra Dubey, an atmospheric scientist at Los Alamos National Laboratory in New Mexico, and an author of an earlier study with similar findings, said the faster rate of warming of the Arctic was worrisome, and pointed to the need to closely monitor the region.

"One has to measure it much better, and all the time, because we are at the precipice of many tipping points", like the complete loss of Arctic sea ice in summers, he said.

The Arctic is heating more rapidly in large part because of a feedback loop in which warming melts sea ice in the region, which exposes more of the Arctic Ocean to sunlight and leads to more warming - this, in turn, leads to even more melting and warming.

The result of this and other oceanic and atmospheric processes is called Arctic amplification.

How the rate of warming in the Arctic is described compared with the global average is related in part to the time period that is analysed and how the region is defined.

The new analysis begins with data from 1979, when accurate temperature estimates from satellite sensors first became available.

The researchers also defined the Arctic as the area north of the Arctic Circle, above about 66 degrees latitude.

Dr Thomas Ballinger, a researcher at the University of Alaska Fairbanks, said that how the region is defined "is a very, very relevant conversation for understanding Arctic change".

A bigger Arctic would include more land, reducing the impact of the ice-ocean feedback on average temperatures.

Dr Ballinger said some of the findings in the Finnish study were especially interesting, including those showing very high rates of warming in the late 1980s and 1990s.

"That really was when Arctic amplification rates were the strongest," he said.

The two studies serve as a sharp reminder that humans continue to burn fossil fuels and pump greenhouse gases into the atmosphere at rates that are dangerously heating the planet and unleashing extreme weather.

Just weeks after a deadly heat wave hit European capitals, shattering records in Britain, extreme temperatures are again engulfing western Europe this week. The heaviest rainfall in decades inundated Seoul, South Korea, killing at least nine people and damaging nearly 3,000 structures.

If the rate of warming in the Arctic continues to speed up, the influence on weather could worsen, one of the researchers said. Projections of future climate impacts might also need to be adjusted, said researcher Mika Rantanen at the Finish Meteorological Institute in Helsinki.

NYTIMES