Burning natural gas emits “far less” carbon dioxide (CO2) than coal but even so, more reliance on gas won’t significantly slow climate change, according to a new study.
With a 50% reduction in the use of coal and a matching increase in the use of natural gas, “worldwide warming would actually increase slightly (less than 0.1 degree Celsius) for the next 40 years as a result of the switch,” according to estimates by the National Center for Atmospheric Research (NCAR). At that point the effects of climate change would be reduced “but only marginally, taking into account current projections that the earth will warm by as much as 3 degrees C (5.4 degrees Fahrenheit) by 2100,” said author Tom Wigley.
“Relying more on natural gas would reduce emissions of carbon dioxide, but it would do little to help solve the climate problem,” said Wigley. “It would be many decades before it would slow down global warming at all, and even then it would just be making a difference around the edges.”
Wigley noted that gas is composed mostly of methane, which he said is a more potent greenhouse gas (GHG) than CO2. Over the life of a gas well methane may escape into the atmosphere through venting or leaking, and it also may leak from gas storage tanks and pipes.
His computer simulations found that because of the methane emissions, a worldwide, partial shift to gas would accelerate climate change slightly “through at least 2050, even if no methane leaked from natural gas operations, and through as late as 2140 if there were ‘substantial’ leaks” of around 10%. After that, more reliance on gas would begin to slow down the increase in global average temperature, but only by a few tenths of a degree.
A controversial study by Cornell University earlier this year reported that methane leaks were a particular concern for natural gas produced from shale formations through hydraulic fracturing (see Daily GPI, April 13). However, the gas industry and some researchers have disputed those findings. IHS Cambridge Energy Research Associates in August said the GHG emissions from shale gas production likely are “significantly overstated” (see Shale Daily, Aug. 25).
But Wigley discovered another potential benefit from burning coal that gas doesn’t provide. Coal use causes warming through its emission of CO2, but “it also releases comparatively large amounts of sulfates and other particles that, although detrimental to the environment, cool the planet by blocking incoming sunlight.” The U.S. Environmental Protection Agency has reported that burning coal and oil emits sulfate aerosols that reflect solar radiation into space, which results in a cooling effect.
“This particle effect is a double-edged sword because reducing them is a good thing in terms of lessening air pollution and acid rain,” Wigley said. “But the paradox is when we clean up these particles, it slows down efforts to reduce global warming.”
The study is to appear in the October issue of the journal Climatic Change Letters.
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