Bob CollinsA lot of people on social media are pointing out that it’s colder in Minnesota and the Upper Midwest than it is in Antarctica, to which others point out that it’s winter in the Upper Midwest and summer in the Southern Hemisphere.
Both are missing an important point.
It’s colder in the Upper Midwest than it is in the Arctic region.
The sun comes up Wednesday in Barrow, Alaska, also known as Utqiagvik, at 11:50 a.m. Its overnight low temperature? Minus 4 — 22 degrees warmer than the Twin Cities.
That’s something to keep in mind when someone wonders where your climate change is now? Take a walk outside. That’s climate change.
Jennifer Francis, the senior scientist at the Woods Hole Research Center in Massachusetts, writes this week that the polar vortex here is accompanied by a heat wave where it should be cold.
There’s science behind it and everything:
Greenhouse gas emissions from human activities have warmed the globe by about 1.8 degrees Fahrenheit (1 C) over the past 50 years. However, the Arctic has warmed more than twice as much. Amplified Arctic warming is due mainly to dramatic melting of ice and snow in recent decades, which exposes darker ocean and land surfaces that absorb a lot more of the sun’s heat.
Because of rapid Arctic warming, the north/south temperature difference has diminished. This reduces pressure differences between the Arctic and mid-latitudes, weakening jet stream winds. And just as slow-moving rivers typically take a winding route, a slower-flowing jet stream tends to meander.
Large north/south undulations in the jet stream generate wave energy in the atmosphere. If they are wavy and persistent enough, the energy can travel upward and disrupt the stratospheric polar vortex. Sometimes this upper vortex becomes so distorted that it splits into two or more swirling eddies.
These “daughter” vortices tend to wander southward, bringing their very cold air with them and leaving behind a warmer-than-normal Arctic. One of these eddies will sit over North America this week, delivering bone-chilling temperatures to much of the nation.
She says this could be a normal pattern for the future although she acknowledges this is a “hot research topic.”
“It’s clear that at times, coping with global warming means arming ourselves with extra scarfs, mittens and long underwear,” she says.
