Climate | Finnish study: The Arctic region is warming no less than four times faster than the rest of the globe

Arctic the region has warmed four times as fast as the Earth on average, according to a new study by researchers at the Finnish Meteorological Institute.

Until now, it has been thought that the rate of warming in the northern regions has been twice the global average.

Researcher at the Department of Meteorology Mika Rantanen says that the difference between the previous estimates and the new estimate can partly be due to which period and which area is considered.

“The Arctic region has not been clearly defined in any way. It is possible that some previous studies have determined the Arctic to be wider, so the ratio decreases, and also used a longer time window,” says Rantanen.

In previous studies, it was also possible to calculate the difference in warming during a time when the warming was less than now.

In the new in their study, Rantanen and his colleagues limited the examination to the area inside the Arctic Circle. In Finland, the border passes at Rovaniemi.

The period spanned from 1979 to 2021, a total of 43 years. Accurate and reliable temperature satellite measurements are available from that time. In addition, strong warming started just in the 1970s.

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“We believe that we have used the most reasonable time window and definition for the Arctic.”

During the review period, the Arctic regions have warmed by 0.75 degrees per decade. That’s four times as much as the rest of the world is warming.

In the Barents Sea, the pace of warming has been no less than 1.25 degrees per decade, or seven times the warming of the rest of the globe.

Arctic warming is mainly promoted by the melting of sea ice. An ice-free sea gives off more heat. At the end of autumn and winter, the arctic region has warmed most strongly precisely because the warm sea surface emits heat into the atmosphere.

In addition, when there is no ice, less sunlight is reflected back into space and remains to warm the Earth.

In addition to warming caused by greenhouse gases, there is long-term natural variability in the climate.

Meteorology according to the department’s research, the climate models that describe and predict climate change have sharply underestimated the difference in the rate of warming between the Arctic region and the rest of the world.

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“If you calculate the average of dozens of different climate models regarding the warming ratio, it is around two and a half. When the current observation is four, the ratio is 40–50 percent higher than the results of climate models. In individual climate model simulations, the warming ratio is almost the same as observed,” says Rantanen.

The estimates of the climate models have gone wrong, possibly because they have not taken the natural variability of the climate into account sufficiently accurately. In addition to warming caused by greenhouse gases, there is long-term natural variability in the climate.

“In climate models, the inherent variability is not in sync with reality. In the models, the variations are a little closer to which decade they happen.”

The natural ones According to Rantanen, climate changes may explain the current situation, where the Arctic region is warming at a fourfold rate.

“If the natural fluctuations turn in the opposite direction and seem to slow down global warming, it is possible that the warming difference will even out.”

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The difference can even out even if the warming of the rest of the world accelerates and catches up with the warming of the Arctic region.

Rantanen and the partners didn’t really figure out how much of the Arctic warming is human-caused and how much is natural variability.

“I dare say that the share of natural fluctuations is significant and it is by no means zero.”

The climate variations are caused, for example, by long-term circulation of sea currents.

According to Rantanen, in recent decades, more warm seawater may have flowed into the northern sea areas than before, which has melted the sea ice and accelerated the warming.

“If the flow movement is weakened and melting is reduced, it may be a natural mechanism that slows down the warming.”

The atmosphere also has decades-long fluctuations. For example, the so-called North Atlantic Oscillation can affect the Arctic climate.

The research by Rantanen and his colleagues was published by the scientific journal Communications Earth & Environment.

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