Friday, June 27, 2014

Study: To address climate change, nothing substitutes for reducing CO2 emissions

Reducing methane emissions wouldn't substitute for reducing CO2, but it should help some, at least. Methane breaks down to CO2. Even a relatively short-lived increase in temperature due to methane, etc. will have feedback effects. Eg., melting polar ice increases the absorption of heat by the earth. I think his point is that people want a quick and easy fix, that entails little inconvenience to them, and will use the reduction of methane, etc. as a means of making themselves feel they can ignore the need to reduce CO2. Also, most people, by training or nature, are not deep thinkers, and will go for simplistic answers.

https://www.democracyforamerica.com/campaigns/3317-friends-and-neighbors-of-curt-thompson

PUBLIC RELEASE DATE: 27-Jun-2014
Contact: Steve Koppes
University of Chicago
Study: To address climate change, nothing substitutes for reducing CO2 emissions

The politically expedient way to mitigate climate change is essentially no way at all, according to a comprehensive new study by University of Chicago climatologist Raymond Pierrehumbert.

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.

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"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.

Perhaps as a result of wishful thinking, the policy implications of those facts had become confused, said Pierrehumbert. Part of the problem is that the statistical tool used to compare the climate effect of gasses is badly flawed. The measure, called Global Warming Potential (GWP), predicts the effect on climate by comparing the emission rate of carbon dioxide with the emission rate of methane. But a one-ton-per-year reduction in the amount of methane emitted translates into a single lowering of the global thermostat, while a one-ton-per-year reduction in CO2 yields a climate benefit that increases over time. That's because each extra ton of CO2 that would have been emitted would have irreversibly ratcheted up the global thermostat by an additional increment.

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Pierrehumbert himself hopes that his work will help lead policymakers to abandon Kyoto-style multi-gas trading schemes, which treat the gasses equivalently, and put the emphasis on CO2 for the next 50 years or so. "I see puncturing the excessive enthusiasm about short-lived climate pollution control as a step in the right direction," he said, "because it takes away one of the grounds for procrastination on CO2. If you're serious about protecting climate, it's the CO2 you've got to deal with first."

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