Madison just set an all-time high temp record for December. Is climate change to blame?

MADISON, Wis. — Wisconsin is known for its cold, snowy winters, but over the past 50 years, average winter temps have crept up by five degrees. On Wednesday, Madison set a record for the warmest December day in the city’s history.

The new record, which hit 68 degrees Wednesday afternoon, beat the previous record from Dec. 3, 2012 by three degrees.

With December temperatures that feel more like October, it might be easy to jump to the conclusion that climate change is directly responsible for the abnormal weather, but experts stress it’s not that simple.

Climate change vs. climate variations

Climate change, in the simplest of terms, can be thought of as the northward shift of traditional climates, John Young, the director of the Wisconsin State Climatology Office, said. Paired with a global increase in temperatures and increased atmospheric moisture, shifting climates can set the stage for record-breaking weather events like Wednesday’s high temperatures.

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Young stressed that climate variations — year-to-year changes in a locale’s weather — also play a role in the likelihood of extreme weather events. Climate variations tend to fluctuate a lot on an annual basis, which means that despite a decades-long warming trend, it’s still possible for one year to be colder and snowier than average and vice versa.

“A warm winter climate still means some monsters, but they will be more infrequent,” Young said. “They’ll be more rare in the future. But when they do come, they are not saying ‘Oh, climate change is not occurring,’ they are ‘Hey, this is natural climate variability.”

Whether it’s unseasonably warm temperatures or powerful tornadoes hitting where they traditionally wouldn’t this time of year, the probability of extreme weather events in the future is increasing because of the long-term trends.

Dr. Jonathan Martin, an atmospheric and oceanic sciences professor at the University of Wisconsin-Madison, said significant individual weather events can happen given natural variability.

“However, when you get one after another after another strange event — we had an unusual tornado and tragic tornado outbreak in Kentucky just earlier this week and now we’ve got (Wednesday’s storm system) on our own back door — you have to start to wonder if the game isn’t a little bit rigged, and I think that it is and that’s where the global warming comes in,” he said.

Global impacts on local systems

A rise in atmospheric moisture means there’s more fuel for severe storms. Those storms, paired with northern-shifting climates, mean places like the Ohio River Valley, which normally wouldn’t expect tornadoes this late in the year, are more vulnerable to those threats.

“You could not attribute the tornadoes in western Kentucky to climate change per se, but the likelihood of the possibility of a tornado there has definitely been increasing due to climate change,” Young said.

More moisture in the air also means more cloud cover, which has implications of its own for places like southern Wisconsin that are used to colder winters. Young said that when he first arrived in Madison some 50 years ago, there were more clear, sunny days which in turn led to bitterly cold nights. With more clouds hanging around at night, it’s more difficult for temperatures to drop and allow bodies of water to freeze.

That has implications for how we enjoy winters, too.

Long-term impacts on Wisconsin winters

Thanks to 140 years’ worth of data, we know the amount of time Lake Mendota is frozen through year after year is on the decline.

“That’s why the ice, even when it’s formed, is sometimes not been as thick as in the old days when you could drive trucks out on the ice and be very comfortable doing it,” Young said. “Especially here in southern Wisconsin, that becomes a very iffy issue.”

RELATED: When will Lake Mendota freeze over this year? Local experts want you to guess

Shifting climate patterns could have an impact on the amount of snow cities like Madison see in the future, too. Because southern Wisconsin is closer to regions that see winter temperatures above freezing, there’s a chance for precipitation from storms that would have normally brought snow to bring rain instead.

“I’m big on probabilities of extreme events,” Young said. “That’s what affect[s] society and the trends in those probabilities are really really important to our future.”

WATCH BELOW: UW-Madison professor talks about Wednesday’s record-breaking heat, climate change