BNC Switching from coal to natural gas would do little for global climate

Switching from coal to natural gas would do little for global climate Barry Brook | 11 September 2011 at 5:40 PM | Categories: Clim Ch Q&A, Emissions, Policy | URL: http://wp.me/piCIJ-1iE

A common refrain from politicians and members of the business community is that moving from coal to natural gas is an effective way to cut carbon dioxide emissions and therefore address global warming. This argument is flawed, as I detailed last year in two posts, Santos Chief's gassy vision (Parts I and II). Yet, gas is still often labelled a 'transition fuel' or 'bridge technology', even by groups that promote large-scale renewables such as the solar-thermal-focused DESERTEC (see here). So how useful is gas for climate change mitigation?
Below is a media release describing a new paper (published in the journal Climatic Change) by my colleague Dr. Tom Wigley (Adjunct Professor at the University of Adelaide) on the impact -- expressed in terms of climate forcing -- of a wholesale switch from coal to gas for electricity generation (i.e., a limit analysis). They key considerations to be modelled are the effects of methane leakage, the extraction method used to supply the gas (e.g., conventional versus shale gas), and the aerosol dimming effect of coal compared to gas (i.e., the story is more complicated than just the greenhouse gas forcing effects, especially on the decadal time scale). Some of you have already mentioned associated news stories on this paper  in the latest Open Thread, but I thought it would be good to present the media release (largely written by Tom), and have a focused post for discussing the paper and its implications.
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Coal to gas: the influence of methane leakage

Although the burning of natural gas emits far less carbon dioxide than coal, a new study concludes that a greater reliance on natural gas would fail to significantly slow down climate change.
The study by Tom Wigley, who is a senior research associate at the National Center for Atmospheric Research (NCAR), underscores the complex and sometimes conflicting ways in which fossil fuel burning affects Earth’s climate. While coal use causes warming through emission of heat-trapping carbon dioxide, 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 situation is further complicated by uncertainty over the amount of methane that leaks from natural gas operations. Methane is an especially potent greenhouse gas.
Wigley’s computer simulations indicate that a worldwide, partial shift from coal to natural gas would slightly accelerate climate change through at least 2050, even if no methane leaked from natural gas operations, and through as late as 2140 if there were substantial leaks. After that, the greater reliance on natural gas would begin to slow down the increase in global average temperature, but only by a few tenths of a degree.
“Relying more on natural gas would reduce emissions of carbon dioxide, but it would do little to help solve the climate problem,” says Wigley, who is also an adjunct professor at the University of Adelaide in Australia. “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.”
The study appears next month in the peer-reviewed journal Climatic Change, and is already available online.

A small impact on temperatures

The burning of coal releases more carbon dioxide than other fossil fuels, as well as comparatively high levels of other pollutants, including sulfur dioxide, nitrogen oxides, and particles such as ash. Since natural gas emits lower levels of these pollutants, some energy experts have proposed greater reliance on that fuel source as a way to slow down global warming and reduce the impacts of energy use on the environment.
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