Houston Chronicle Sunday

Arctic is warming faster than previously described

- By Henry Fountain

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

Over the past four decades, the region has been heating up four times faster than the global average, not the commonly reported two to three times. And some parts of the region, notably the Barents Sea north of Norway and Russia, are warming up to seven times faster, they said.

Although scientists have long known that average temperatur­es in the Arctic are increasing faster than the rest of the planet, the rate has been a source of confusion. Studies and news accounts have estimated it is two to three times faster than the global average.

Mika Rantanen, a researcher at the Finnish Meteorolog­ical Institute in Helsinki, said he and his colleagues decided to look at the issue in the summer of 2020, when intense heat waves in the Siberian Arctic drew a lot of attention.

“We were frustrated by the fact that there’s this saying that the Arctic is warming twice as fast as the globe,” Rantanen said. “But when you look at the data, you can easily see that it is close to four.”

The new findings are bolstered by those of another recent study, led by scientists at Los Alamos National Laboratory in New Mexico, which found similar rates of warming, although over a different time span.

The greater warming has effects in the Arctic, including faster melting of the Greenland ice sheet, which leads to greater sealevel rise. But it also affects atmospheri­c circulatio­n in North America and elsewhere, with impacts on weather such as extreme rainfall and heat waves, although some of the impacts are a subject of debate among scientists.

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, which 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 analyzed and how the region is defined.

The new analysis, published in the journal Communicat­ions Earth and Environmen­t, 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.

Thomas Ballinger, a researcher at the University of Alaska Fairbanks, said the issue of 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.

Ballinger, who was not involved in either study, is an author of the annual Arctic Report Card prepared for the National Oceanic and Atmospheri­c Administra­tion. He 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.

Rantanen said his group’s results also suggest a role of natural variabilit­y in the rate of warming, perhaps some longterm changes in ocean or atmospheri­c circulatio­n.

But clearly the sea iceocean interactio­n is most important, he said.

“The warming trends are quite strongly coupled with the decline of sea ice,” he said. “They’re highest over those areas where the sea ice has been declining the most. That’s the primary reason.”

 ?? New York Times file photo ?? A new analysis shows the Arctic has been heating up four times faster than the global average.
New York Times file photo A new analysis shows the Arctic has been heating up four times faster than the global average.

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