People who claim that “the science is settled” on global warming have to be pretty unsettled by the science news in the last week.
“Setttled science”, of course, means that we are inevitably headed toward a disastrous warming of surface temperatures as forecast by some computer models, and we therefore need an international carbon tax or cap-and-trade system, pronto.
Settled science would know all of the important “forcings” and “feedbacks” in the climate system, such as the sensitivity of surface temperature to changes in carbon dioxide (a forcing) and the behavior of clouds, which could either enhance or counter warming (a feedback).
Now it appears that cloud tops are lowering, a totally unforeseen cooling feedback on carbon dioxide-induced warming. Writing in Geophysical Research Letters, University of Auckland’s Roger Davies and Matthew Molloy conclude this could be a “significant measure of a negative cloud feedback to global warming”.
The average global cloud height is linked to the average global temperature—generally, the higher the average cloud height, the higher the average surface temperature, and vice versa. The tie-in is related to the height in the atmosphere from which clouds radiate infrared radiation to space. The higher up they are, the cooler they are, and they dissipate less radiation, which means the surface stays warmer.
Problem is that there’s only ten years of data, and there was a pretty decent La Nina (that’s the cold side of El Nino) in the Pacific Ocean in 2008, which was clearly correlated with a decline in cloud top height. Davies and Molloy are therefore properly cautious with their conclusions, but nonetheless note that a comparison of the beginning and endpoints for their study, which minimizes the La Nina contribution, still showed a decline in cloud height.
Who’d a thunk this one? Based upon data from the paper, the cooling climate impact from the decrease in the average global cloud height more than offset the positive forcing from an increase in greenhouse gases from human activities in the last decade.
This is—yet another—explanation in the refereed literature to apologize for recent climate misbehavior. Others include changes in the sun, cruddy air from China, and a change in stratospheric water vapor.
The last one is especially interesting because that, too, is a previously unknown forcing on climate, i.e. another bullet shot at “settled science”.
Then there’s the new icing on the global warming cake. Data from 2003 through 2010 from the Gravity Recovery and Climate Experiment (GRACE) satellite show virtually zero net melting from the massive Himalayan ice cap, the world’s “third pole”. The UN, using an unrefereed publication from the World Wildlife Federation, erroneously forecast in its last climate compendium that it would be gone by 2035. In reality, it will last hundreds of years, and even longer if the current trends reflect how the ice cap reacts to warming.
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