Regional extreme cold events despite global warming
The first week of January 2014 had an extreme cold event affecting the Midwest , eastern and southeastern United States.
How extreme was it? 100 year low-temperature records for those particular dates were broken at as many as 50 NOAA weather stations scattered across this region, but it did not break any all-time records or even records for the month of January for any of those same cities.
It was very, very cold, with an incursion of Arctic air reaching all the way to Florida and made more bitter by strong winds, but it did not last more than a few days. Normal winter temperatures are expected for the rest of January.
During this period, the jet stream developed a pattern of extreme North-South meanders, and the polar vortex, which normally holds the coldest polar air in place, became distorted. This allowed a major outbreak of Arctic air to bring extreme cold to much of the United States.
Historically, such events have happened in this region once every five to ten years, and one this strong had not been felt since the 1990s, so the cold of early January represents a normal weather fluctuation and does not change the overall trend of warming temperatures. In the US contiguous 48 states during the last 15 years, monthly high temperature records have been broken more than twice as often as monthly low temperature records, and as global warming continues this pattern will grow even stronger.
Because cold snaps like this are related to exaggerated meanders in the jet stream, not all mid-latitude regions are affected in the same way at once. In early January of 2014, while parts of the continental United States experienced severe cold, Alaska, Europe, Scandanavia and parts of Russia were actually having warm spells due to the same exaggerated jet-stream pattern. The Arctic itself is warmer than usual during such breakouts of cold air to the South, so the regional cold snap, however severe, does not indicate a global cold snap, and our globe continues to grow warmer.
See also these NOAA articles:
- Polar vortex brings cold here and there, but not everywhere
- Wobbly polar vortex triggers extreme cold air outbreak
Category: What's With the Weather