Wednesday, December 30, 2015

Connecting the Extreme Weather Events

If you look at a weather map from this week, it looks like the flooding in Missouri and England and the melting at the North Pole are all connected. On the map, the warm moist air originates in the El Niño-influenced eastern tropical Pacific. It moves north, and colder air in the Rocky Mountains pushes it east. The warm air mass crosses the Caribbean and the North Atlantic Ocean, somehow holding together all the way to the North Pole.

Of course, a meteorologist would explain it differently, perhaps in terms of a counterclockwise flow around a cold air mass, but any way you look at it, it adds up to unusual weather patterns in far-flung places. In my own local area we have seen record high temperatures in the past week. The flood events in the United States and England certainly qualify as disasters, but it is the Arctic melt event just days after the winter solstice that is the most ominous effect. The Greenland ice sheet is protected from rapid summer melting by the heat taken up in the melting sea ice nearby. For that to happen, new sea ice has to form at this time of year. Missing two weeks of refreeze won’t have much impact, but if the Arctic Ocean sees five or six weeks of melt conditions one winter, that puts the world well on our way to a rapid Greenland melt-out.