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Mild Winter In Wisconsin Goes Deeper Than Just Climate Change

Wisconsin's mild winter is a combination of many factors including sudden stratospheric warming reducing the effects of the polar vortex.

Wisconsin has seen a fairly mild winter this year. Some may point to climate change as the cause of this issue, but UW-Milwaukee professor and leading forecast expert Paul Roebber says the answer is much more complicated than that.

He says that while the Earth is warming, that is not a major effect on day-to-day weather. Something, he says, that's had a larger short-term impact on this winter was an instance of sudden stratospheric warming.

“There is this phenomenon called sudden stratospheric warming, it doesn’t happen every year, but it leads to some pretty disruptive patterns in the weather, in the winter weather patterns, and there’s an indication that something did disrupt the polar vortex this winter in late December,” says Roebber.

In past winters, the polar vortex can often have large amounts of very cold air that breaks off and brings very cold temperatures. Famously this happened in Jan. 2019 and led to Wisconsin declaring a state of emergency.

Roebber says that the sudden stratospheric warming doesn’t mean Wisconsin won’t see colder temperatures in the second half of winter but “it’s not obvious that, that’s going to happen.”

With any weather predictions, they are just highly education predictions, and anything further than five days can be hard to get an accurate read, Roebber explains, and a mild winter is not a predictor for spring or summer.

“The winter has what’s called a chaotic pattern, which sort of — it’s not actually random, it has a pattern to it — effectively makes it impossible to predict beyond a certain timeline,” he says. “Because of that, it sort of resets the conditions for the spring and the subsequent summer and so it’s really hard to be able to say much about what those patterns will look like because of the randomizing affect.”

The effects of the milder winter are wide reaching.

Industries based on winter experiences like downhill or cross-country skiing have to rely on manufactured snow and icier conditions if the temperatures get above freezing during the day.

“Even though the ski hills can manufacture snow, people often don’t go if they don’t see snow all around them, so that has a negative influence,” he says.

Another important effect is on insects, as deep freezes are what help control insect populations.

“If you don’t have really hard freezes, sometimes insect populations can really begin to grow and don’t die out over the winter, so you can have really significant impacts on agriculture as one example,” he says.

So enjoy the mild winter while it’s here, and don’t put too much stock in what it means for the future.

Joy is a WUWM host and producer for Lake Effect.
From 2020 to 2021, Jack was WUWM's digital intern and then digital producer.