Climate Change Does Not Cause Extreme Winters in the Northeast

It turns out that cold snaps, like the ones that hit the eastern United States over the past few winters, are not connected with climate change. Scientists have found that global warming actually reduces temperature variability rather than increasing it and causing extreme winters.

Repeated cold snaps drove temperatures far below freezing across the United States in the past two winters. It became so cold that part of Niagara Falls froze, and ice floes formed on Lake Michigan. These low temperatures had been rare in recent years, and people wondered whether or not climate change could be responsible for the most recent extreme events.

Some have argued that amplified warming of the Arctic relative to lower latitudes in recent decades has weakened the polar jet stream, a strong wind current several kilometers high in the atmosphere driven by temperature differences between the warm tropic and cold polar regions. One hypothesis is that a weaker jet stream may become more wavy, leading to greater fluctuations in temperatures in mid-latitudes. In other words, a warming Arctic could contribute to the cold snaps that have hit the eastern U.S.

In order to find out if this is true, the researchers used climate situations and theoretical arguments to show that in most places, the range of temperature fluctuations will decrease as the climate warms. Not only will cold snaps become rarer simply because the climate is warming, but their frequency will be reduced because fluctuations about the warming mean that temperature also becomes smaller.

"Despite lower temperature variance, there will be more extreme warm periods in the future because the Earth is warming," said Tapio Schneider, one of the researchers, in a news release. "The waviness of the jet stream that makes our day-to-day weather does not change much."

The findings are published in the Journal of Climate.

For more great science stories and general news, please visit our sister site, Headlines and Global News (HNGN).