Chuck Bednar for redOrbit.com – @BednarChuck
A harsh winter cold spell that affected much of the Eastern US last month may have shattered record low temperatures that had stood for decades, but it was not the result of climate change, according to researchers from ETH Zurich and the California Institute of Technology.
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In fact, events experienced in that part of the country over the past two winters may have caused part of Niagara Falls to freeze and ice floes to form on the Great Lakes, but incidents like this are actually becoming increasingly rare in recent years due to reduced temperature variability.
It has been argued that the amplified warming of the Arctic relative to lower latitudes which has taken place over the past few decades has weakened the polar jet stream, including a hypothesis that suggests that the strong atmospheric wind current has become increasingly wavy, leading to an increase in temperature fluctuations in the middle latitudes due to global warming.
As a result of this wavier jet stream, amplified Arctic warming may have contributed to the cold snaps that hit the eastern US, the hypothesis claims. However, in a recent issue of the Journal of Climate, the authors of the new study come to a drastically different conclusion.
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A more stable temperature
Using climate simulations and theoretical arguments, they demonstrated that in most places the range of temperature fluctuations will decrease as the climate warms. This means that these cold spells will become fewer and further between due to the warming climate, and that the frequency of such events will be reduced as fluctuations of mean temperatures is also reduced.
In the study, the ETH Zurich and Caltech scientists report that higher latitudes are warming more quickly than lower latitudes, meaning that the temperature difference between the equator and the poles is decreasing. If this temperature variation disappeared entirely, air masses would have the same temperature regardless of whether or not the flowed from the north or south.
Theoretically, this would completely eliminate temperature variability altogether, and while this scenario will never happen, it helped guide the study author’s approach. They used a simplified climate model to verify their hypothesis using various scenarios, and found that the mid-latitude temperature variability decreased as differences between the poles and equator diminished.
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Climate model simulations by the Intergovernmental Panel on Climate Change (IPCC) showed similar results, the researchers noted: as the climate warms, temperature differences in the mid-latitudes decrease, as does temperature variability, particularly during the winter. However, this does not mean that there will be no extreme temperatures in the future, they added.
Get ready: hotter summers are coming
“Despite lower temperature variance, there will be more extreme warm periods in the future because the Earth is warming,” explained lead author Tapio Schneider. Schneider’s team limited their work to temperature trends, however, meaning that as other studies have indicated, severe storms and other extreme events could still become more common due to global warming.
The researchers said that they want to further investigate the potential implications of these findings in future studies.
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