Is climate change behind this month's winter tornadoes?

caution tape around a damaged building following a storm
Wreckage from Arcadian Bank lines a street in Hartland, Minn., following a severe storm on Thursday. Minnesota saw it’s first December tornado Wednesday, after a swarm of deadly tornadoes swept through the Midwest days earlier.
Tim Evans for MPR News file

Minnesota has seen it all lately: summer-like thunderstorms and a tornado — the first confirmed tornado touchdown in Minnesota in December just days after digging out from several inches of snow. And we aren't the only ones experiencing abnormal winter weather. Unusually warm air is behind last week's deadly tornado outbreak in the Midwest.

Can we expect more unstable winter weather as the planet warms? University of St. Thomas professor John Abraham joined Climate Cast this week from New Orleans, where climate experts from across the country are meeting for the American Geophysical Union conference this week.

You can hear his and host Paul Huttner’s conversation using the audio player above. You can read a transcript of it below.

What we're finding is that tornadoes are occurring earlier in the year and later in the year, typically times when it would be too cold to have tornadoes. Because of global warming, tornadoes can form when they otherwise couldn't.

In addition, it appears that we're seeing larger groups of tornadoes form. So rather than one or two tornadoes, a number of tornadoes all formed together.

In Minnesota this week, we experienced that same kind of storm with unprecedented warmth. The fact that it's happening this far north with this much warm air — temperatures into the 60s in Minnesota in December — that to me screams ‘climate change signal.’ What are your thoughts on that?

You're exactly right. And it's really something to be concerned about because it's a connection between what we're doing to the atmosphere and the extreme weather that we are experiencing on the planet.

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Minnesota winters on average have warmed about five or six degrees since 1970. But what about this more unstable weather? Can we expect potentially more severe weather eating at the fringes of winter in Minnesota?

That's exactly what we expect. In Minnesota over the last couple of weeks, we went from heavy snow to extreme warmth, and then go back to being winter again. That kind of seesaw swinging back and forth is characteristic of what happens in a warming climate.

What are some of the other main themes that you're hearing about at the American Geophysical Union conference?

There was a bombshell this week: a study that dealt with rapidly melting ice in Antarctica that has really dropped a grenade into this entire conference and is really raising some alarm bells.

Frankly, most of us didn't anticipate this study coming out. So we're all abuzz about melting ice at the South Pole.

And that was thought to be a slower process, right? But am I correct in hearing that there are some indications that the Thwaites Glacier ice shelf could fail within just five years?

Yeah, that's the concern. So the part of the glacier that is at the land-water interface is melting much more rapidly than we had anticipated, and there's a concern that portion of the glacier will break off within five years.

Just that one portion of Antarctica by itself could raise ocean waters by 2 feet, and that would have major consequences all around the world.