9/25/13, "Were Colorado floods result of global warming? Probably not." CSMonitor.com, Amanda Paulson
"The statistics for the storm that produced the Colorado floods are
stunning. But there was a very similar storm in 1938, suggesting nature
can surprise even without human help."
"The record-breaking storm that caused the Colorado
floods has been called a “thousand-year event,” leading to speculation
about whether the storm and flooding owed anything to climate change. The answer, of course, is impossible to know for sure. But according
to a panel of climate scientists from Colorado, the storm likely had
little to do with climate change and more to do with an unusual
confluence of atmospheric events.
It’s possible that some shifts
due to climate change, such as increased water vapor in the air, may
have exacerbated the effects of the storm slightly. But a storm in
September 1938 was very similar in its footprint, its timing, and the
type of rainfall (which was not the brief, intense thunderstorms typical
here).
“Having seen the September 1938 analog should somewhat humble us, and
remind us that nature has a way of delivering without human
intervention in the climate system,” says Martin Hoerling, a research
meteorologist at NOAA’s Earth System Research Laboratory in Boulder, Colo.
“Climate change is operating, there’s no question about that,
and water
vapor has gone up,” but in this instance, climate change “really wasn’t
a factor.”Most striking about the recent storm was the sheer amounts of
rain that fell in some areas. It set a new one-day record
for rainfall in Boulder, 9.08 inches, that is almost double the previous
record of 4.8 inches, set in 1919. The town, which averages just over
20 inches of rainfall in a year, has received 17.59 inches so far in
September.
The storm was caused by a confluence of several unusual
factors. A low-pressure system along the Utah-Nevada border helped pull
a heavy plume of tropical moisture up from Mexico, a high-pressure
system to the east pushed up even more moisture from the Gulf of Mexico,
and a stalled front generated lift. All those factors set up a
“blocking pattern” that helped keep the storm hovering over the same
period for a long time.
Those events combining are highly unusual,
said Klaus Wolter, a NOAA climate researcher who spoke at a panel
discussion hosted by the Cooperative Institute for Research in
Environmental Sciences (CIRES) at the University of Colorado and NOAA.",,,via Junk Science
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