University lecturer Isaac Held and his colleagues published a letter in “Science” on Feb. 14 arguing that the recent extreme cold temperatures experienced in the Northeast were not due to human-induced global warming but were instead caused by natural fluctuations in the climate.
Held was joined in writing the letter by University of Washington professor John Wallace, Colorado State University professor David Thompson, University of Alaska Fairbanks professor John Walsh and Kevin Trenberth at the National Center for Atmospheric Research.
The letter argues against the claim that human-induced global warming could result in more frigid winters. The letter also argues that statements that the polar regions have recently begun warming more rapidly than the rest of the world are inconclusive.
“I don’t think that’s the case. I think it’s been warming more rapidly more along,” Held said, referring to the polar regions. Held is both a lecturer in the Princeton Program in Atmospheric and Oceanic Sciences and a scientist with the Geophysical Fluid Dynamics Laboratory and the National Oceanic and Atmospheric Administration.
The letter references research published in the Geophysical Research Letters suggesting that global warming could perturb the polar vortex and cause both more extreme cold and extreme warm, saying that results of this research were unsubstantiated and have not been supported by the models proposed by many climate scientists. The polar vortex is a ring of Westerlies, prevailing winds that blow from west to east around the poles that are strongest in the winter, Wallace explained. Wallace is a professor of atmospheric sciences at the University of Washington.
Wallace noted that the vortex continually changes its shape, and when its lobes sweep down over temperate areas, those regions get periods of cold weather.
“I don’t think the slowing down of the polar vortex is enough to really affect behavior of the vortex very much,” he said.
He also noted that the belief that human-induced climate change could cause more extreme cold was, in fact, held by only a small minority of researchers.
“The reason we wrote the letter is because of our concern that this is getting picked up by the press and presented as if it were part of the consensus about global warming,” Wallace said, referencing the claim that climate change results in more frigid winters.
Held noted that global warming could cause more extreme droughts and wet periods as the atmosphere begins to hold more water vapor. However, he added that not all extreme weather patterns can be explained by climate change.
“We expect hurricanes to become more intense as the climate warms, but I don’t think we expect storms at temperate latitudes … to become more extreme,” Held said, adding that fierce storms could simply be due to natural fluctuations.
Like Held, University Physics professor William Happer said this year’s weather is not anomalous.
“It’s exactly the same as weather we’ve had in my own lifetime many times,” Happer said. “Why should it suddenly be climate change?”