Our climate is changing. The past two decades have been Wisconsin’s warmest on record, and last winter marked the state’s warmest since 1895, when people started keeping track.
So, how is this winter measuring up? We look at winter trends and their ripple effects with Wisconsin State Climatologist Steve Vavrus.
Sitting in his office on the UW-Madison campus, Vavrus reflects on what Wisconsin experienced last winter.
“We had a really severe snow drought in much of the state especially up north and it was economically devastating for a lot of resorts up there. The tourism industry took a big hit. Very little lake ice. A lot of communities had to cancel ice festivals, snow sculpting festivals and so on. Ecological impacts with the reduced snow cover and lake ice cover that we’re still trying to figure out," Vavrus says.
While he hesitates calling any season normal, Vavrus says this winter started off with a more typical December.
“January interestingly here at least in southern Wisconsin has been colder than normal by a few degrees. Normally that wouldn’t be so memorable or meaningful but so few months lately have been colder than normal at all,” Vavrus says.
As for lake ice cover, “We definitely have much more extensive ice cover around Wisconsin this winter. We did have the big warm-up in late December,” Vavrus says. He watched the warming unfold in real time in Madison.
“We have a really long ice record on Lake Mendota going back to the early 1850s. It temporarily froze on Christmas Day and then didn’t last more than two days and then melted off. Then it froze for good beginning Jan. 7. And because we’ve had such cold weather ever since, we have a pretty solid ice cover on Mendota, but it’s still not safe enough to be out on,” Vavrus says.
We had this conversation a few weeks ago. In the meantime, Vavrus says the ice has gotten thicker and much safer.
Winter, he says, is our most variable season.
“We have variability in Wisconsin in every season, of course, but winter is the most. And we see that even day to day—we can drop to 20 below zero, and then in another day or two later, we’re up in the 30s. And so that can make it difficult to tease out a long-term warming signal,” he says.
But Vavrus says temperatures are unmistakably trending upward.
“We see that as an unmistakable downward trend in ice cover—the amount of ice cover, the days with ice cover, the thickness of ice. Those are all shrinking, and that’s consistent with the overall warming climate,” Vavrus says.
There’s more to be learned. Vavrus and fellow researchers are exploring what sounds like a simple question.
“Are Wisconsin’s winters getting snowier? And that’s surprisingly difficult to answer. We have different pieces of data that we’re analyzing. We have made some progress in the last year... The significant statewide trend that appears to be occurring since 1895 is primarily happening in the northern third of Wisconsin,” he says.
Vavrus realizes that information might seem implausible.
“One possibility is because winters are getting more moisture in the air in a warming climate. We do know that the winters have been seeing more precipitation overall. And so, we could be getting more snowfall, but then we have more winter warmups, and the snow doesn’t last as long. Now we have more bare ground than we used to,” he says.
Vavrus studies the drivers but says it’s critical to look at warming winters holistically.
Take Wisconsin’s logging industry. “Trucks can’t drive on muddy soils, and that’s been happening more and more, so that directly affects their operations and the economy,” Vavrus says.
He points to impacts of unreliable snowpack—not just to wildlife, but to agriculture too. “Even this winter, it’s been cold, but we haven’t had a lot of snow cover. How is that affecting frost depth and eventually runoff and the potential killing of plants because it gets too cold for their roots?” Vavrus says.
