WASHINGTON — Has Earth's fever broken?
Official government measurements show that the world's temperature has cooled a bit since reaching its most recent peak in 1998.
That's given global warming skeptics new ammunition to attack the prevailing theory of climate change. The skeptics argue that the current stretch of slightly cooler temperatures means that costly measures to limit carbon dioxide emissions are ill-founded and unnecessary.
Proposals to combat global warming will "destroy more than a million good American jobs and increase the average family's annual energy bill by at least $1,500 a year," the Heartland Institute, a conservative research organization based in Chicago, declared in full-page newspaper ads earlier this summer.
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Many scientists agree, however, that hotter times are ahead.
"The preponderance of evidence is that global warming will resume," Nicholas Bond, a meteorologist at the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory in Seattle, said in an e-mail.
According to data from the National Space Science and Technology Center in Huntsville, Ala., the global high temperature in 1998 was 1.37 degrees Fahrenheit above the average for the previous 20 years. So far this year, the high has been less — only 0.76 degrees Fahrenheit above the 20-year average.
Scientists say the skeptics' argument is misleading.
"It's entirely possible to have a period as long as a decade or two of cooling superimposed on the long-term warming trend," said David Easterling, chief of scientific services at NOAA's National Climatic Data Center in Asheville, N.C.
"These short-term fluctuations are statistically insignificant (and) entirely due to natural internal variability," Easterling said in an essay in the journal Geophysical Research Letters in April.
Climate experts say the 1998 record was partly caused by El Niño, a periodic warming of tropical Pacific Ocean waters.
El Niño is returning this summer after a four-year absence and is expected to hang around until late next year.
"If El Niño continues to strengthen as projected, expect more (high-temperature) records to fall," said Thomas Karl, director of the National Climatic Data Center in Asheville.