By: Dr. Michael Meyer
“Climate skeptics” often point to episodic extreme winter weather, such as the 2017/2018 polar outbreak, as evidence that climate change science is incorrect. If one were to delve into the topic a bit further, it becomes apparent that this recent cold spell could be consistent with evolving climate change theory.
A commonly heard conception:
The current cold spell is evidence against climate change theory.
The current cold spell is consistent with elements of evolving climate change theory.
A Washington Post article from January 4, 2018 describes how cold waves such as we have just experienced may be a feature of a changing winter—as you will see, in the northern hemisphere only the eastern US experienced below normal temperatures recently.
There’s a lot we don’t know—but we do know that climate change will give us different winters.
To gain a Wisconsin perspective, I asked Dr. Steve Vavrus with UW Atmospheric Sciences to share his understanding of the relationship between receding Arctic Sea ice and periodic polar outbreaks such as that we just experienced. Dr. Vavrus is an expert on Arctic climate and its impact on mid latitude regions such as the Upper Midwest. The following is his response.
Funny you should ask, because I’m currently working on a review article for a journal that addresses this very topic. I’ll have a firmer answer to your question when I finish the draft in a couple months, but I can give some preliminary comments for now. As someone actively engaged in researching this question, I happen to support the contention that the warming Arctic is affecting our weather patterns by promoting a slower and more meandering jet stream. During winter, this change favors the kind of cold-air outbreaks we’ve been experiencing lately, but there are so many other confounding factors that determine our weather at a given time.
I would say that the scientific community has moved toward acceptance of the idea that enhanced Arctic warming is affecting mid-latitude circulation and weather patterns, but there are different opinions about exactly how and how much. The slew of research on this topic in recent years has revealed that this linkage is more complicated than originally supposed and is probably episodic and regionally dependent. I agree with this scientific consensus and would liken the Arctic’s impact to loading dice: the extra heat being pumped into the Arctic atmosphere from the increasingly warm polar lands and oceans is likely to favor a slower and sinuous jet stream, but this tendency can easily be countered in a given year by other random factors such as El Nino. This is a fascinating subject and one that will undoubtedly receive a lot more attention in coming years.
Climate science is rapidly evolving as new information and knowledge is gained. The take-home message from this recent cold spell is that it indeed may be another manifestation of the changes brought about by a warming planet. It is a complicated system to model as Dr. Vavrus points out, but cold winters do not, by definition, dismiss the scientific consensus that a warming planet is related to human activity.
Michael W. Meyer Ph.D., is on the Board of Directors of Wisconsin’s Green Fire and the chair of WGF’s Climate Change Working Group. He is also a research scientist with NOVA Ecological Sciences in Arbor Vitae, Wisconsin.