This is usually the coldest time of the year at the North Pole, where the sun won’t rise until March 20. But recently there’s been a historic thaw. Indeed, last weekend the temperature rose above freezing, to 35 degrees, at the pole. Scientists have recorded what they call a warm air intrusion through the central Arctic this winter. In the area north of 80 degrees latitude, temperatures are 36 degrees above normal. Such intrusions have become more frequent and more intense. There were only four between 1980 and 2010, but now there have been four in the past five years.…
