Ever since the Intergovernmental Panel on Climate Change acknowledged that the ominous rise in Earth's mean surface temperature had begun to slow in 1998, scientists have struggled to explain this puzzling "pause" or "hiatus" in warming.
Some have argued that dust and ash blasted into the sky by Mount Pinatubo and other volcanoes had reflected the sun's heat back into space before it could be trapped by greenhouse gases. Others hypothesized that the sun had entered a rare period of calm, temporarily interrupting its habit of explosive tantrums.
Still more insisted this "missing" heat was absorbed by the Pacific Ocean, and other waters, and still lurks deep below the waves awaiting a stormy return to the surface.
On Thursday, however, researchers at the National Oceanographic and Atmospheric Administration published yet another explanation in the prestigious journal Science.
Their assessment: The hiatus never happened.
In an argument that drew criticism from both sides of the rancorous debate over man-made climate change, NOAA researchers wrote that long-existing instrument biases have masked rising sea surface temperatures.
Once those biases are accounted for, "this hiatus or slowdown simply vanishes," said lead study author Thomas Karl, of NOAA's Climatic Data Center.
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Karl and his colleagues insist that global average surface temperature has climbed 0.2 degrees Fahrenheit each decade since 1950, without interruption, due to the heat-trapping effects of man-made gases.
Not surprisingly, this conclusion was quickly dismissed by so-called climate-change skeptics -- those scientists and policy groups who say the hiatus proves climatologists have greatly miscalculated the warming effects of fossil fuel emissions.
"The main claim, that it uncovers a significant recent warming trend, is certainly dubious," wrote a panel of climatologists at the libertarian Cato Institute.
"I don't find this analysis at all convincing," wrote Judith Curry, a climate scientist at Georgia Tech. "While I'm sure this latest analysis from NOAA will be regarded as politically useful for the Obama administration, I don't regard it as a particularly useful contribution to our scientific understanding of what is going on."
More surprising, however, was the fact that researchers on the opposite side of the debate also rejected the idea of a vanishing slowdown.
"It is a bit misleading to say there is no hiatus," said climate scientist Kevin Trenberth of the National Center for Atmospheric Research.
"I would argue the study is misleading on the implications of its results," said Piers Forster, an atmospheric physicist at the University of Leeds, in England. "This study has not 'magiced' the hiatus away or somehow corrected the IPCC."
