Dan Shapley / News Editor
Most U.S. states recorded average 2006 temperatures that ranked in the top 10 ever recorded -- and that heat was fueled primarily by global warming, U.S. scientists say.
Greenhouse gases -- like the carbon dioxide that spits out of car tailpipes and power plant smokestacks -- accounted for more than half the heat across the continental United States last year, with natural factors accounting for the other half, according to the study, to be published next week in the scientific journal Geophysical Research Letters, scientists at the National Oceanographic and Atmospheric Administration.
The 2006 average temperature across the United States ranked second to 1998, the team of scientists from NOAA's Earth System Resesarch Lab in Boulder, Colo. said. Record keeping began in 1895, and the 2006 average temperature was more than 2 degrees above the 20th Century average, and marked the ninth consecutive above-normal year. NOAA
Further, the chance of record-setting heat is now 15 times more likely than in pre-industrial times because of the level of greenhouse gas pollution that has filled the atmosphere. The research was intended to separate the effects of El Nino -- the warming of the east tropical Pacific Ocean -- from global warming trends.
The effect of the past 10 El Nino events, since 1965, has been a general cooling across the U.S. Despite the presence of an El Nino in 2006, temperatures neared record-breaking levels. The scientists attributed that primarily to greenhouse gases, which trap heat from the sun near the earth's surface, by analyzing 42 climate simulations from 18 mathematical models.
"The U.S. temperature pattern of widespread warming was completely inconsistent with the pattern expected from El Nino, but it closely matched the expected effects of greenhouse warming," the NOAA press release stated. Likewise, the record-setting 1998 temperature was recorded during an El Nino year. As for this year, the scientists estimate that there's a 16% chance 2007 will break the temperature record set in 1998.
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