Climate Intel: What's with the Cold Weather?
Governor Dayton cancelled K-12 public schools in Minnesota due to extreme cold and severe winter weather on January 6. On that frigid Monday morning the ambient temperature at the Grand Marais airport was -31 degrees F and the wind howled at 21mph creating the coldest spot in Minnesota at -63 degrees F.1
The steely grip of winter that is confounding much of the United States has many Minnesotans recalling severe winters of yore, like in 1994 when then—Governor Carlson ordered schools to close due to extreme cold ... and he gave the same order two more times in ensuing years.2
But what about now? Now, the phrase "polar vortex" has crept out of the climatologist's milieu into mainstream newscasts. This high altitude feature of Earth's atmosphere is a very normal but very persistent large-scale cyclone located near each of the planet's geographical poles.3 These low-pressure systems typically strengthen in winter and weaken in summer. When the polar vortex is strong, the Westerlies blow harder; when it weakens, the flow pattern buckles and cold air escapes into mid-latitudes. It seems that in January 2014, cold air escaped the Arctic vortex and raced south across much of North America.
This year's spate of extreme cold events have led to questions about how changes in Earth's atmosphere could be creating warmer temperatures in the Arctic that are weakening the vortex and therefore leading to more cold weather outbreaks in the mid-latitudes. In a two-minute video released by the White House, science advisor Dr. John Holdren explains why we might expect to see more extreme cold events in the future.4 In the video, Holdren explains that the temperature difference between the Arctic and the mid-latitudes is shrinking and that temperature difference is what drives the polar vortex.
It bears repeating that a single event, no matter how cold or wet or windy, can't
be attributed to a changing climate; however, by looking at trends and projections it appears we would be wise to brace for increased variability and frequency of extreme events in the United States. While some view January's extreme cold as a reason to scoff at reports of global warming, science indicates that the sub-zero conditions are indeed consistent with climate change scenarios.
1Minnesota Climatology Working Group. Arctic Cold Blast: January 5-7, 2014.
2Minnesota Climatology Working Group. Historic Wind Chill Temperatures in Minnesota. January 7, 2014.
3NOAA Climate.gov. Wobbly polar vortex triggers extreme cold air outbreak. January 8, 2014.
4Dr. John Holdren. 2014. Video.
Tollefson, Jeff (08 January 2014). US cold snap fuels climate debate. Nature.
By Hilarie Sorensen