NEW YORK (AP) — Last year brought a record heat wave to Texas, massive
floods in Bangkok and an unusually warm November in England. How much has
global warming boosted the chances of events like that?
Quite a lot in Texas and England, but apparently not at all in Bangkok, say
new analyses released Tuesday.
Scientists can’t blame any single weather event on global warming, but they
can assess how climate change has altered the odds of such events happening,
Tom Peterson of the National Oceanic and Atmospheric Administration told
reporters in a briefing. He’s an editor of a report that includes the
analyses published by the Bulletin of the American Meteorological Society.
In the Texas analysis, researchers at Oregon State University and in England
noted that the state suffered through record heat last year. It happened
during a La Nina weather pattern, the flip side of El Nino. Caused by the
cooling of the central Pacific Ocean, La Nina generally cools global
temperatures but would be expected to make the southern United States warmer
and drier than usual. But beyond that, the scientists wondered, would global
warming affect the chances of such an event happening?
To find out, they ran a lot of computer simulations of Texas climate during
La Nina years. They compared the outcome of three such years in the 1960s
with that of 2008, which was used as a stand-in for 2011 because they were
unable to simulate last year. The idea, they said, was to check the
likelihood of such a heat wave both before and after there was a lot of
man-made climate change, which is primarily from burning fossil fuels like
coal and oil.
Their conclusion: Global warming has made such a Texas heat wave about 20
times more likely to happen during a La Nina year.
Using a similar approach, scientists from Oxford University and the British
government looked at temperatures in central England. Last November was the
second warmest in that region in more than 300 years. And December 2010 was
the second coldest in that time.
Their analysis concluded that global warming has made such a warm November
about 62 times more likely, and such a cold December just half as likely.
Kevin Trenberth, of the National Center for Atmospheric Research’s climate
analysis section, said that he found the Britain study to be reasonable,
given what he called a flawed climate model. As for the Texas result, he
said that given how the study was done, the calculated increase in
likelihood “could well be an underestimate.”
A third analysis considered unusually severe river flooding last year in
central and southern Thailand, including neighborhoods in Bangkok. It found
no sign that climate change played a role in that event, noting that the
amount of rainfall was not very unusual. The scale of the flooding was
influenced more by factors like reservoir operation policies, researchers
Also at the briefing, NOAA released its report on the climate for 2011,
which included several statistics similar to what it had announced earlier.
Last year was the coolest since 2008 in terms of global average temperature,
but it still remained among the 15 warmest years since records began in the
late 1800s, the agency said. It was also above average for the period
Online: NOAA: http://www.climate.gov