Matt Ridley: Whatever happened to global warming?

Via Mark Perry. Excerpts:

"The climate-research establishment has finally admitted openly what skeptic scientists have been saying for nearly a decade: Global warming has stopped since shortly before this century began.

First the climate-research establishment denied that a pause existed, noting that if there was a pause, it would invalidate their theories. Now they say there is a pause (or “hiatus”), but that it doesn’t after all invalidate their theories.

Alas, their explanations have made their predicament worse by implying that man-made climate change is so slow and tentative that it can be easily overwhelmed by natural variation in temperature—a possibility that they had previously all but ruled out.

It has been roughly two decades since there was a trend in temperature significantly different from zero. The burst of warming that preceded the millennium lasted about 20 years and was preceded by 30 years of slight cooling after 1940 (see chart).

Most science journalists, who are strongly biased in favor of reporting alarming predictions, rather than neutral facts, chose to ignore the pause until very recently, when there were explanations available for it. Nearly 40 different excuses for the pause have been advanced, including Chinese economic growth that supposedly pushed cooling sulfate particles into the air, the removal of ozone-eating chemicals, an excess of volcanic emissions, and a slowdown in magnetic activity in the sun.

The favorite explanation earlier this year was that strong trade winds in the Pacific Ocean had been taking warmth from the air and sequestering it in the ocean. This was based on a few sketchy observations, suggesting a very tiny change in water temperature—a few hundredths of a degree—at depths of up to 200 meters.

Last month two scientists wrote in Science that they had instead found the explanation in natural fluctuations in currents in the Atlantic Ocean. For the last 30 years of the 20th century, Xianyao Chen and Ka-Kit Tung suggested, these currents had been boosting the warming by bringing heat to the surface, then for the past 15 years the currents had been counteracting it by taking heat down deep.

The warming in the last three decades of the 20th century, to quote the news release that accompanied their paper, “was roughly half due to global warming and half to the natural Atlantic Ocean cycle.” In other words, even the modest warming in the 1980s and 1990s—which never achieved the 0.3 degrees Celsius per decade necessary to satisfy the feedback-enhanced models that predict about three degrees of warming by the end of the century—had been exaggerated by natural causes. The man-made warming of the past 20 years has been so feeble that a shifting current in one ocean was enough to wipe it out altogether."

From Cafe Hayek

"The U.N. no longer claims that there will be dangerous or rapid climate change in the next two decades. Last September, between the second and final draft of its fifth assessment report, the U.N.’s Intergovernmental Panel on Climate Change quietly downgraded the warming it expected in the 30 years following 1995, to about 0.5 degrees Celsius from 0.7 (or, in Fahrenheit, to about 0.9 degrees, from 1.3).

Even that is likely to be too high. The climate-research establishment has finally admitted openly what skeptic scientists have been saying for nearly a decade: Global warming has stopped since shortly before this century began."

"Putting the icing on the cake of good news, Xianyao Chen and Ka-Kit Tung think the Atlantic Ocean may continue to prevent any warming for the next two decades. So in their quest to explain the pause, scientists have made the future sound even less alarming than before."