Temperatures have been measured at the Franco-Italian Concordia station in Antarctica that are about 45 degrees above average. Which reported international media in recent days. And last week there were already reports of extremely high temperatures on the other side of the world, in the Arctic.
What’s going on at the poles?
On March 18, the mercury rose to -11.5°C at the Concordia research station, while it averages around -55°C at this time of year. “Such warming is more extreme than we expected based on climate models,” says Michiel van den Broeke, professor. polar meteorology at Utrecht University He compares it with the heat wave in Canada last July, when it became 49.6°C in the town of Lytton.
For the Arctic, the excitement was not about actually measured temperatures, but about a weather forecast. In a tweet dated March 13 Climate researcher Martin Stendel of the Danish Meteorological Institute (DMI) announced that “in the next few days” temperatures in the central Arctic region would rise 20 degrees above the long-term average (1979-2000). With that they would rise above the ocean around the freezing point, and above land (on Spitsbergen, for example) even far above. Stendel announced via email this Monday that the prediction “indeed has come true”. Temperatures around freezing have been measured on the east coast of Greenland. “That’s very warm for the season.” According to Stendel, the warm period lasted about three days.
Warming world
These signals are part of a warming world, says Van den Broeke. As the climate warms, the extremes become greater. Van den Broeke: “The temperature record in Antarctica could not have happened if the atmosphere had not already warmed up in the past century”.
This is especially true for the Arctic, which is warming two to three times faster than the global average. The World Weather Attribution, which examines the background of extreme weather events that have occurred, wrote about the unprecedented heat wave that occurred in November and December 2016 in the central part of the Arctic, which it is now an event that occurs every 50 to 200 years. If warming were to increase further to an average of 2°C – for the Arctic this would mean +5°C – such a heat wave would repeat every few years.
While the outlier in Antarctica was unprecedented, this is not the case in the Arctic, says Stendel. “We’ve had some similar heat waves in recent years.” But he says temperatures have reached “the absolute maximum” expected for this area and this time of year.
Warm air currents
In both Antarctica and the Arctic, warm air currents penetrated far into the Arctic from lower latitudes. In Antarctica, those currents came from Australia. In the Arctic, it was a warm air flow that moved northwards between a strong low pressure area over Denmark and a strong high pressure area over northwestern Russia.
Van den Broeke links the fact that the temperature rise at the Concordia research station can be so great to the breaking through of a stubborn cold layer on the surface. The station is located on the ice cap, at an altitude of more than 3,200 meters. “A very cold layer of air, a few hundred meters thick, forms there, a process that cannot be disturbed so quickly that far inland, at the start of the polar winter,” says Van den Broeke. But if it does happen, because of clouds or a warm air current, the temperature can rise very quickly.
It is precisely this strong layering of the sky that makes it difficult for Antarctica to make predictions, say Van den Broeke and Stendel. The climate models would have to have a much higher resolution for this. “That is still too computationally demanding,” says Van den Broeke. Stendel: “Maybe with the next generation of supercomputers.”