America
Extreme winter not a result of climate change: Study
Washington, March 28
Contrary to popular
belief, cold snaps like the ones that hit the eastern United States in
the past winter are not a consequence of climate change, says a new
study.
The results, published in the Journal of Climate, showed that global warming actually tends to reduce temperature variability.
Repeated
cold snaps led to temperatures far below freezing across the eastern
United States in the past two winters. Parts of the Niagara Falls froze,
and ice floes formed on Lake Michigan.
But scientists at ETH
Zurich in Switzerland and the California Institute of Technology in the
US led by Tapio Schneider, professor of climate dynamics at ETH Zurich,
found that the extreme winters were not a result of climate change.
They
used climate simulations and theoretical arguments to show that in most
places, the range of temperature fluctuations will decrease as the
climate warms.
So not only will cold snaps become rarer simply
because the climate is warming. Additionally, their frequency will be
reduced because fluctuations about the warming mean temperature also
become smaller.
However, Schneider noted that "despite lower
temperature variance, there will be more extreme warm periods in the
future because the Earth is warming".
Using a highly simplified climate model, they examined various climate scenarios to verify their theory.
It
showed that the temperature variability in mid-latitudes indeed
decreases as the temperature difference between the poles and the
equator diminishes.
Climate model simulations by the
Intergovernmental Panel on Climate Change (IPCC) showed similar results:
as the climate warms, temperature differences in mid-latitudes
decrease, and so does temperature variability, especially in winter.
Temperature
extremes will therefore become rarer as this variability is reduced.
But this does not mean there will be no temperature extremes in the
future, the researchers added.