"Based on these model runs, my take is the loss of sea ice so far hasn't been large enough to have a really big effect in the mid-latitudes over all these other things that influence weather [in that part of the world]," Screen said.
Polar changes may outpace analysis
But as Francis and others point out, the Arctic has only been this warm for a short time. Perhaps the failure to find statistically significant changes is simply due to that.
"It is only in the last 15 years or so that we have been able to see this really starting to kick in," Francis said. "And that's part of the reason that when you do trend analysis, it's hard to detect a trend."
National Oceanic and Atmospheric Administration scientist James Overland, who has long studied the Arctic, said he viewed the work by Barnes and Screen as too "conservative."
"Scientists are trained to be careful in their analysis and to prove results beyond a doubt. Their work is a contribution to the science. But in the real world of climate change we do not have this full luxury," Overland wrote in an email.
As Overland, Francis and many others in the community point out, the changes the Arctic is experiencing are fast, real and profoundly unsettling, especially for those who have studied the region for decades.
Arctic sea ice extent continues to plunge below average each summer. Measurements have shown that the winds that blow west to east and drive the jet stream are weakening because of the region's warming. By 2035, some scientists say, the Arctic could be ice-free in the summer.
All this, say Francis and others, has to have an effect on the jet stream and the weather. Even in the work of Barnes and Screen, whose research contradicts that of Francis, the Rutgers scientist sees support for her hypothesis. She says although they do not find statistically significant changes in waviness, the trends they document go in the right direction.
"As time goes on, I think those statistics will start to become more robust," Francis said.
As a pioneer of a compelling new explanation for how a warming Arctic could be changing how the atmosphere works, Francis will undoubtedly see more challenges to, and work in support of, her hypothesis.
She also frankly acknowledges that the story is not yet clear and the science is still emerging.
"I'm also the first to recognize there is a lot more going on than just the Arctic warming," Francis said.
Mounting interest in the linkage
This September, the National Academy of Sciences is sponsoring a workshop with around 50 scientists to discuss the topic of a warming Arctic and its affects on weather. Since the field is so young, one of the prerogatives is setting a research agenda, said Cecilia Bitz, a polar climate scientist at the University of Washington who is on the workshop's organizing committee.
Bitz said the idea of a linkage between a rapidly warming Arctic and changes in mid-latitude weather is intriguing and plausible, but her mind is still open about whether it is true.
"The back-and-forth you see in the literature doesn't surprise me, because the data sets are short and there are different ways of defining weather," she said.
Bitz believes more modeling studies could help sort out the issue. Both she and Exeter's Screen suggested that perhaps one of the reasons researchers are getting contradictory results is that the effect of a warmer Arctic on mid-latitude weather, even if it exists, just might not be big enough to measure.
"If there is a signal, it's quite small; it's quite weak; it's quite hard to identify with the noise in the climate system," Screen said.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500