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 defining the region “is a very, very relevant conversation to understanding Arctic change.” A larger Arctic would include more land, reducing the impact of ice-ocean feedback on average temperatures.
Dr. Ballinger, who was not involved in either study, is the author of the annual Arctic report prepared for the National Oceanic and Atmospheric Administration. He said some of the findings from the Finnish study were particularly interesting, especially those showing very high warming rates in the late 1980s and 1990s. arctic amplification were the strongest,” he said.
The previous study, published last month in Geophysical Research Letters, looked at data from 1960 and defined a larger Arctic, north of 65 degrees latitude, that includes more land. He found that the rate of warming had reached four times the global average from about 20 years ago. And unlike the Finnish study, it found that there were two two-decade periods, from the mid-1980s to the mid-1990s and into the 2000s, with big jumps in warming in the region.
“It’s not changing continuously, it’s changing in stages,” said Los Alamos atmospheric scientist Manvendra K. Dubey. And because the data covers periods of decades, it suggests a link to natural climate variability, as well as warming resulting from increased greenhouse gas emissions from human activity.
Dr Rantanen said his group’s results also indicate a role played by natural variability in the rate of warming, possibly long-term changes in ocean or atmospheric circulation.