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Global Warming Pause: What Climate Scientists Predicted in 2009

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Robert Bradley Jr, Master Resource

“Pauses as long as 15 years are rare in the simulations, and ‘we expect that [real-world] warming will resume in the next few years,’ the Hadley Centre group writes…. Researchers … agree that no sort of natural variability can hold off greenhouse warming much longer.” —– Richard Kerr. What Happened to Global Warming? Scientists Say Just Wait a Bit.”  Science, October 1, 2009.

Debates over the ‘pause’ or ‘hiatus’ of global warming since its El Nino-driven peak back in 1998 should not forget the false confidence of leading alarmist scientists were saying less than a decade ago about how the warming slowdown was surely coming to an end. After all, model-predicted warming was the best indication of reality if the models had the right physics in them (a Big if).

Flash back to 2009 when Richard A. Kerr, the longtime, award-winning climate-change scribe for Science magazine, the flagship publication of the American Association for the Advancement of Science, penned “What Happened to Global Warming? Scientists Say Just Wait a Bit.

Kerr framed the debate in political terms with Copenhagen just ahead—and failed to interview or include the low-sensitivity scientists who would have been closer to the mark.

The blogosphere has been having a field day with global warming’s apparent decade-long stagnation. Negotiators are working toward an international global warming agreement to be signed in Copenhagen in December, yet there hasn’t been any warming for a decade. What’s the point, bloggers ask?

Climate researchers are beginning to answer back in their preferred venue, the peer-reviewed literature. The pause in warming is real enough, but it’s just temporary, they argue from their analyses.

A natural swing in climate to the cool side has been holding greenhouse warming back, and such swings don’t last forever. “In the end, global warming will prevail,” says climate scientist Gavin Schmidt of NASA’s Goddard Institute for Space Studies (GISS) in New York City.

The latest response from the climate community comes in State of the Climate in 2008, a special supplement to the current (August) issue of the Bulletin of the American Meteorological Society. Climate researcher Jeff Knight and eight colleagues at the Met Office Hadley Centre in Exeter, U.K., first establish that—at least in one leading temperature record—greenhouse warming has been stopped in its tracks for the past 10 years.

In the HadCRUT3 temperature record, the world warmed by 0.07°C±0.07°C from 1999 through 2008, not the 0.20°C expected by the Intergovernmental Panel on Climate Change. Corrected for the natural temperature effects of El Niño and its sister climate event La Niña, the decade’s trend is a perfectly flat 0.00°C.

So contrarian bloggers are right: There’s been no increase in greenhouse warming lately. That result came as no surprise to Knight and his colleagues or, for that matter, to most climate scientists. But the Hadley Centre group took the next step, using climate modeling to try to quantify how unusual a 10-year warming pause might be.

In 10 modeling runs of 21st century climate totaling 700 years worth of simulation, long-term warming proceeded about as expected: 2.0°C by the end of the century. But along the way in the 700 years of simulation, about 17 separate 10-year intervals had temperature trends resembling that of the past decade—that is, more or less flat.

From this result, the group concludes that the model can reproduce natural jostlings of the climate system—perhaps a shift in heat-carrying ocean currents—that can cool the world and hold off greenhouse warming for a decade. But natural climate variability in the model has its limits. Pauses as long as 15 years are rare in the simulations, and “we expect that [real-world] warming will resume in the next few years,” the Hadley Centre group writes.

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