Climate Scientist: It’s ‘Reasonable’ to Believe Global Warming Is Causing Snowy Winters

Christopher Neefus | February 3, 2011 | 6:11pm EST
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Polar bear walking on ice (USFWS photo)

A prominent climate scientist says it is reasonable to conclude that global warming has caused the unusually snowy weather in the eastern United States and Europe over the past two winters, but stresses that this is only a hypothesis that has yet to be definitively demonstrated.

Dr. Mark Serreze, director of the National Snow and Ice Data Center (NSIDC), a federally-supported research unit at the University of Colorado, told that the hypothesis is that the decline in Arctic sea ice in recent years has created more open water in the Arctic in summertime, and that this open water absorbs more heat during the summer than the former icepack did, then releases that heat during the winter months, warming the Arctic itself, while pushing cold Arctic air down over the eastern United States and Europe.

“Here’s what happens and here’s what a lot of people get really screwed up on, and it’s straightforward,” Serreze told “All right, so it’s getting warmer, and what is happening is that we’re not growing as much ice in winter as we used to be, but we’re melting a heck of a lot more in the summer than we used to.

“So, now what happens is that if we look at the end of summer, end of the melt season in the Arctic—September, say, specifically September--what you find is that there’s much, much more open water than there used to be,” said Serreze. “But what has happened is because that open water is very dark it’s been absorbing a lot of solar heat through the summer."

“So now you’ve got this ocean with all this heat in it that it didn’t used to have. Autumn comes, the sun sets in the Arctic, that heat gets released back to the atmosphere,” he said. “And so what’s happening is the atmosphere gets warmed, because the ocean is losing its heat back to the atmosphere. That’s why you get this big warming in the Arctic in the autumn and through the winter, because it’s releasing that heat back.

“So you say it’s related to the ice melt. Yes, it is,” said Serreze. “But actually there’s a seasonal lag to it. It’s actually, the ice is melting in summer, exposing all this dark open ocean, picking up all this heat, and, then, autumn comes, the sun sets, that heat’s got to go back to the atmosphere, and that’s what it does. And that greatly warms up the Arctic relative to where it used to be--in other words, relative to, say, where we were 30 years ago. And what’s happening is that that is starting to change the sort of basic temperature gradients in the atmosphere that I talked about before.

“And so if you do that, the thinking is that could actually let this cold air in the Arctic kind of start to spill south,” said Serreze. “Now you say, ‘Well, hasn’t the air been warmed?’ Yes, it has, but it’s still cold air, though.

“But that’s the thinking,” Serreze explained. “The thinking is that, to put it in another way, we’ve put now a heat source in the Arctic that there didn’t used to be. And if we do that, the thinking is the atmosphere—the circulation of the atmosphere—responds to that. It feels that heating and responds to that. And one possible outcome of that is you get this sort of pattern that you’re seeing here for the last couple winters, that you’ve had cold and snowy over the eastern U.S., especially over Europe, but at the same time this extremely warm Arctic."

“I mean that’s basically it in a nutshell,” said Serreze.

Serreze, whose team monitors the amount of sea ice present in the Arctic over time, told that this is one line of thought being pursued in the scientific community.

NSIDC scientists use data from the National Aeronautics and Space Administration (NASA) to measure how many square miles of sea ice are present in the Arctic each day, and calculate the average monthly ice coverage. They then post this information and their analysis of it on their website.

In their analysis of the Arctic sea ice extent for January 2001, which was posted on February 2, the scientists said there was an average of only 5.23 million square miles of ice covering the Arctic seas. That is the lowest average Arctic ice extent for January since satellites began recording Arctic sea ice in the late 1970’s.

The NSIDC analysis of January’s Arctic sea ice includes a section titled, “Potential links with mid-latitude weather.” The analysis explores the idea that the diminished Arctic ice cover has contributed to colder, snowier winters in Europe and the Northeastern United States.

“Cold air is denser than warmer air, so it sits closer to the surface,” NSIDC says in its analysis. “Around the North Pole, this dense cold air causes a circular wind pattern called the polar vortex , which helps keep cold air trapped near the poles. When sea ice has not formed during autumn and winter, heat from the ocean escapes and warms the atmosphere. This may weaken the polar vortex and allow air to spill out of the Arctic and into mid-latitude regions in some years, bringing potentially cold winter weather to lower latitudes.”

“For example, the last two winters over the East have been cold and snowy,” explained Serreze. “So what happens there? Well, what you’re looking at is some kind of change in the atmospheric circulation, that basically you’ve got this cold, Arctic air plunging down—clearly, because that’s exactly what’s happening—and that gives you a temperature contrast and that’s what gives you the storms, okay?” Serreze said.

“So this all kind of fits together,” said Serreze. asked Serreze, “I was hoping you could sort of unpack it for me in terms of: We’re linking global warming to a smaller ice cap to this air being forced … into the mid-latitudes? Is that an accurate characterization?”

“Well, yeah, I think it’s reasonable,” said Serreze.

“The question being asked here: Is there something about the weather that—this crazy winter weather that you’re getting here--that might be kind of forced by something?” said Serreze. “Is there something out there that’s changing, that might actually force the big-scale weather pattern to give you that cold stuff out in the Northeast? And this is where this Arctic stuff comes in, what’s happening in the Arctic comes in.”

Serreze stressed that the idea that Arctic warming was causing winter storms in the mid-latitudes was as yet a theory not a proven fact.

“Now saying this, (I’ve) got to stress here that there is no real smoking gun here yet,” he said. “There’s some physical reasoning behind this as I’ve talked about. There’s evidence from climate models that such a thing can happen. There’s some limited observational evidence for it, okay. But no one has the answer yet, and this is very, very much in sort of a—you know, it’s cutting edge stuff.

“No one really knows for sure, and so we really need to look at this problem a lot harder and we need to see what’s, is this pattern going to continue, this funny winter pattern,” he said. “Are we going to see it next year?

“Those are the sort of questions we’re asking,” he said.

“Maybe this is a transient thing that we’re seeing,” he said. “Maybe it’s that at the state of the sea ice cover we see now, this is the response of the atmosphere. Maybe 20 years down the road, it changes. We don’t know. In other words, what I’m saying, just getting rid of more ice doesn’t mean that winters in New York City are going to become colder and snowier with time. It doesn’t necessarily mean that.”

“But it could?” asked.

“Well, yeah, I mean as a scientist, of course, we're very circumspect about these sorts of things and love to couch these things in uncertainty because these are the things we damn well don’t know.”

You can listen to the full interview with Dr. Mark Serreze here:

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