Global warming? Not in Bangkok

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 yesterday.

Scientists can't blame any single weather event on global warming, but they can assess how climate change has altered the frequency of such events, Tom Peterson of the National Oceanic and Atmospheric Administration said. He's an editor of a report on the analyses published by the Bulletin of the American Meteorological Society.

In the Texas analysis, researchers noted that the state suffered through record heat last year. It happened during a La Niña weather pattern, the flip side of El Niño. Caused by the cooling of the central Pacific Ocean, La Niña 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 computer simulations of Texas, and concluded that global warming has made such a Texas heat wave about 20 times more likely to happen during a La Niña year.

Scientists from Oxford University and the British government looked at temperatures in central England and concluded that global warming has made a warm November in England about 62 times more likely, and such a cold December just half as likely.

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, noting that the amount of rainfall was not very unusual.

NOAA noted that last year was the coolest since 2008 in terms of global average temperature, about 57.9 degrees Fahrenheit. Yet it was among the 15 warmest years since the late 1800s, and above average for the period 1980-2010.