Q&A: Is Arctic warming fueling severe winter weather in the mid-latitudes?

We caught up with James Overland, oceanographer at NOAA’s Pacific Marine Environmental Lab, to hear about his latest research on whether Arctic warming is fueling more severe winter weather in the mid-latitudes, the temperate zone of the Earth between the tropics and the Arctic, and the part of the United States where most Americans live.

What is the news in your perspective piece out today in Nature Climate Change?

We got together a diverse, international group of scientists who study whether rapid Arctic warming is influencing extreme weather events in the northern mid-latitudes. We agreed that there is no simple cause-and-effect relationship between a warming Arctic and an emerging pattern of severe winter weather in the mid-latitudes. It’s much more complicated, with different connections in different regions and under different background climate conditions.

Why has this issue been so controversial among scientists?

It’s controversial because there are two basic camps. One group of researchers suggests that
regularly occurring changes in climate patterns or natural variability is the leading cause of the recent severe winter weather events we’ve seen, particularly in the eastern United States. Another group finds possible connections between the warming of the Arctic – melting sea ice, warming air temperatures, rising sea surface temperatures – and the emerging pattern of severe cold winter weather events in the mid-latitudes.

Did you find any consensus in this new research?

What’s new about our research is that a diverse group of scientists from both sides of the debate are now agreeing that the pattern of severe cold winters in the mid-latitudes is primarily based on the state of the jet stream, which is naturally variable. In years when the jet steam is wavy, we are seeing episodes of severe cold plunging down into the mid-latitudes and persisting for weeks. But in the years when jet stream winds flow strongly from west to east and are not  wavy, we tend to have normal winter weather in the mid-latitudes. Strong west to east flowing wind holds Arctic cold in the Arctic, while the wavy pattern allows for this cold to plunge south, as it did in the eastern U.S. during winters of 2009/10, 2010/11, 2013/14, and 2014/15.

Is climate change playing a role in this severe cold weather?

We’ve always had years with wavy or not wavy jet stream winds, but what we are seeing is that the warming Arctic may be loading the dice and reinforcing the wavy patterns, making for extreme cold periods in places like the United States East coast. It’s been even more pronounced in central and eastern Asia.

Why does this research matter?

If we can improve our ability to predict how climate changes are affecting jet stream wind patterns, we will be able to improve our long-term prediction of winter weather in some of the most populous parts of the world. This would have tremendous value to communities, businesses, and entire economies around the northern hemisphere. Society could better prepare for severe winter weather and have the information to make life-saving and cost-saving decisions.

For more information, please contact Monica Allen, director of public affairs for NOAA Research at 301-734-1123 or by email at monica.allen@noaa.gov