Phys.Org - Without Actual Reductions In CO2 Output, Other Actions Useless, Whatever Politics Dictate

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Among the climate pollutants humans put into the atmosphere in significant quantities, the effects of carbon dioxide (CO2) are the longest-lived, with effects on climate that extend thousands of years after emissions cease. But finding the political consensus to act on reducing CO2 emissions has been nearly impossible. So there has been a movement to make up for that inaction by reducing emissions of other, shorter-lived gasses, such as methane, hydrofluorocarbons, and nitrous oxide, and particulates such as soot and black carbon, all of which contribute to warming as well. Pierrehumbert 's study shows that effort to be, as he puts it, a delusion. "Until we do something about CO2, nothing we do about methane or these other things is going to matter much for climate," he said.

Pierrehumbert is the Louis Block Professor in Geophysical Sciences at UChicago, and holder of the King Carl XVI Gustaf Chair in Environmental Sciences at Stockholm University for 2014-2015. His study, published in Annual Review of Earth and Planetary Sciences, brings together findings from the scientific literature with new research and analysis. Its conclusions are clear.

"Ray convincingly shows the benefit and importance of doing everything we can to lower CO2 emissions, and as soon as possible," said Katherine H. Freeman, professor of geosciences at Pennsylvania State University. "We should lower short-lived pollutants like methane too. But, as he makes clear, we should not let them distract us from the urgent need to stop burning fossil fuels."

The basic physics of climate pollutants has been well known for a long time. The warming effect of methane and other short-lived climate pollutants disappears quite quickly after the pollutants are removed from the atmosphere. When you remove them, you get a one-time-only, lump-sum benefit. CO2, on the other hand, lingers in the atmosphere. And if you are still emitting CO2 while you are reducing methane and its fellows, that additional CO2 continues to affect the climate for thousands of years.

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http://phys.org/news/2014-06-climate-substitutes-co2-emissions.html