Does Human-caused Climate Change Impact Tornadoes? The Scientific Jury
Is Still Out
http://www.takepart.com/article/2013/05/21/does-climate-change-impact-tornados
Scientists don't yet have enough data to determine if twisters, like
the one that destroyed Moore, Oklahoma, are enhanced by climate
change.
There's no debating the devastation of the two-mile-wide tornado that
leveled much of Moore, Oklahoma, yesterday, May 20. The Oklahoma City
suburb, situated right in the heart of Tornado Alley, suffered
unimaginable loss of life and destruction: 24 deaths, including nine
children, and an untold number of pulverized buildings, including
schools and hospitals.
But, is this particular type of extreme weather caused by climate
change?
Short answer: Depends on whom you ask and how you ask it.
While the head of the Intergovernmental Panel on Climate Change
(IPCC), Rajenda Pachauri, says that this tornado cannot be pinned on
climate change, some scientists are starting to connect the dots
between global warming and stronger tornadoes.
The IPCC�s special report on managing extreme risks states: �There is
low confidence in observed trends in small spatial-scale phenomena
such as tornadoes and hail because of data inhomogeneities and
inadequacies in monitoring systems.�
In laymen�s terms: We don�t have enough data to measure, since the
United States only began keeping reliable tornado records in 1953, and
Doppler radar wasn�t used for weather until the 1970s.
On the other hand: An increase in tornadoes is consistent with the
warmer, wetter world created by climate change, and particularly large
and unprecedented tornado events may represent the results of climate
disruption.
�As far as climate change is concerned, there will likely be a greater
clashing of cold air masses from the north with even warmer, even more
humid air masses coming off the Gulf of Mexico�conditions that are
favorable for breeding destructive storms,� says Michael Mann, climate
scientist at Pennsylvania State University and author of The Hockey
Stick and the Climate Wars.
�The wildcard is the sheer�we don�t know with certainty whether that
will increase or not in the key regions for tornado formation as a
result of climate change,� Mann continues. �But if one factor is
likely to be favorable, and the other is a wildcard, it�s still more
likely that the product of the two factors will be favorable. Thus, if
you�re a betting person�or the insurance or reinsurance industry for
that matter�you�d probably go with a prediction of greater frequency
and intensity of tornadoes as a result of human-caused climate
change.�
Kevin Trenberth, head of the Climate Analysis Section at the USA
National Center for Atmospheric Research, does the math: �The climate
change effect is probably only a 5 to 10 percent effect in terms of
the instability and subsequent rainfall, but it translates into up to
a 33 percent effect in terms of damage. (It is highly nonlinear, for
10 percent it is 1.1 to the power of 3 = 1.33.) So there is a chain of
events and climate change mainly affects the first link: the basic
buoyancy of the air is increased. Whether that translates into a
super-cell storm and one with a tornado is largely chance weather.�
By meteorological standards, the Moore, Oklahoma, tornado was a
common, garden variety twister: warm humid air meeting a strong jet
stream with strong winds, in the middle of Tornado Alley, during prime
tornado season (May and June) and during the prime tornado hours (late
afternoon).
The only abnormal thing about this tornado was its sheer size. The
climate dice have indeed been loaded for bigger and badder supercells.
--
"God wanted me to be in bed with the maid."