Feb 27, 2018

Arctic warming: scientists alarmed by 'crazy' temperature rises

by
Jonathan Watts
,
The Guardian
‘This is an anomaly among anomalies’: temperatures in parts of the Arctic have recently risen well above average Photo: Ralph Lee Hopkins, National Geographic/Getty Creative/Getty Images
‘This is an anomaly among anomalies’: temperatures in parts of the Arctic have recently risen well above average Photo: Ralph Lee Hopkins, National Geographic/Getty Creative/Getty Images

An alarming heatwave in the sunless winter Arctic is causing blizzards in Europe and forcing scientists to reconsider even their most pessimistic forecasts of climate change.

Although it could yet prove to be a freak event, the primary concern is that global warming is eroding the polar vortex, the powerful winds that once insulated the frozen north.

The north pole gets no sunlight until March, but an influx of warm air has pushed temperatures in Siberia up by as much as 35C above historical averages this month. Greenland has already experienced 61 hours above freezing in 2018 - more than three times as many hours as in any previous year.

Seasoned observers have described what is happening as “crazy,” “weird,” and “simply shocking”.

“This is an anomaly among anomalies. It is far enough outside the historical range that it is worrying – it is a suggestion that there are further surprises in store as we continue to poke the angry beast that is our climate,” said Michael Mann, director of the Earth System Science Center at Pennsylvania State University. “The Arctic has always been regarded as a bellwether because of the vicious circle that amplify human-caused warming in that particular region. And it is sending out a clear warning.”

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The cause and significance of this sharp uptick are now under scrutiny. Temperatures often fluctuate in the Arctic due to the strength or weakness of the polar vortex, the circle of winds – including the jetstream – that help to deflect warmer air masses and keep the region cool. As this natural force field fluctuates, there have been many previous temperature spikes, which make historical charts of Arctic winter weather resemble an electrocardiogram.

But the heat peaks are becoming more frequent and lasting longer – never more so than this year. “In 50 years of Arctic reconstructions, the current warming event is both the most intense and one of the longest-lived warming events ever observed during winter,” said Robert Rohde, lead scientist of Berkeley Earth, a non-profit organisation dedicated to climate science.

The question now is whether this signals a weakening or collapse of the polar vortex, the circle of strong winds that keep the Arctic cold by deflecting other air masses. The vortex depends on the temperature difference between the Arctic and mid-latitudes, but that gap is shrinking because the pole is warming faster than anywhere on Earth. While average temperatures have increased by about 1C, the warming at the pole – closer to 3C – is melting the ice mass. According to Nasa, Arctic sea ice is now declining at a rate of 13.2% per decade, leaving more open water and higher temperatures.