By JR on Wednesday, September 14, 2011
I had a tough time picking a good hyperbolic title for this one, because I had my choice of so many good ones. Last week a new study reported that replacing coal with natural gas might actually worsen climate change in the short term. The study was done by Tom Wigley, who is a senior research associate at the National Center for Atmospheric Research (NCAR). The title of the study is Coal to gas: The influence of methane leakage and will be published in next month’s Climatic Change Letters.
What the study projects is that the amount of methane leaking from gas wells will influence the future temperature rise from climate change: The higher the methane leakage, the higher the future temperature.
Since there is always some methane leakage, and because methane is a very strong greenhouse gas, it was widely reported that the predicted poor showing of natural gas in the short term was due to the gas leakage. More importantly, the widely-reported message relayed by the media is that this study shows that natural gas can’t do much to mitigate climate change.
Ah, but there is a catch that hasn’t gotten much attention (and has been in some cases purposely suppressed).
Notice that the projected temperature increases in every case — even when there is no methane leakage. That indicates that something else is going on here, which is explained in the following story (which is where I got my headline):
Natural Gas Would Speed Up, Not Reduce, Global Warming: Study
Advocates for natural gas drilling have trumpeted its environmental benefits as an alternative to the coal that produces most of America’s electricity, noting that natural gas emits about half the amount of carbon dioxide when burned as coal does.
But a new study sheds doubt on that claim, finding that a shift from coal to natural gas would in fact accelerate the planet’s rising temperatures before slightly reducing them. Tom Wigley of the National Center on Atmospheric Research found that swapping the two fuels would increase global temperatures over the next four decades by about a tenth of a degree.
Wigley’s study does not dispute the fact that natural gas produces far less carbon dioxide, a key culprit in pushing temperatures steadily upwards. But coal also gives off sulfates and other particles that dissipate more quickly than coal fumes and effectively reflect sunlight away from the earth, cooling rather than warming. Those particles do increase air pollution and the likelihood of acid rain, but from a global warming perspective they are a source of relief.
Did you follow that? Coal has higher particulate emissions that increase air pollution, but they help reflect the sun away from the earth. Thus, cities like Linfen, China, pictured below, are sitting in the catbird seat as far as global warming goes. As you can see, no global warming concerns for them as the particulate emissions are quite effectively preventing sunlight from reaching the surface:
So as Linfen, China switches to natural gas (which they have in fact been doing), it will simply speed up global warming. Now I suspect you are beginning to see that this story may be more complex than the refutation of natural gas that the media headlines have indicated.
Since the graphic shows that even zero leakage of methane caused the projected temperature to rise, I was curious as to just how much of the effect was due to the emissions of the coal plants themselves. So I contacted Tom Wigley, the author of the paper, and posed the following question: “Is it true per your models that if we switched from coal to a zero emissions source of electricity that the short-term climate change impact would also be negative due to the loss of the cooling effect from coal’s particulate emissions?”
He replied to my e-mail fairly quickly: “Yes. This “problem” was first pointed out by me in 1991. I’ll attach this paper, plus the coal-to-gas paper. In 1991 I did not consider carbonaceous aerosols. The issue of balancing the disbenefit of less aerosols implies warming vs the benefit of less SO2 emissions implies pollution benefits is a tricky one.” (The 1991 paper he referred to was “Could Reducing Fossil-Fuel Emissions Cause Global Warming?” — published in Nature).
So there you have it. Per this study, shutting down all coal-fired power plants and not even replacing them would cause the temperature to increase in the short term because of the loss of sunlight-reflecting pollutants. Thus, the real story here is about the secondary effect of coal-fired power plants and not about any deficiencies of natural gas.
More HERE (See the original for links, graphics etc.)