Thursday, 29 September 2011

Switching to gas may accelerate warming

Canberra Times
24 Sep 2011, Page: 10

Switching from coal-fired power stations to gas could actually speed up climate change over the next few decades, according to new research challenging accepted wisdom about low-emissions fuel. Although burning natural gas generally releases fewer greenhouse emissions than coal, the latter releases sulfates and other particles that cool the Earth by blocking some of the sun's light. The study, published in the peer reviewed journal Climatic Change Letters, measured the relative impact of the two fuels and found using more gas would "slightly accelerate" the rate of global warming until at least 2050.

Study author Tom Wigley, a co-director of the US National Centre for Atmospheric Research and an adjunct professor at the University of Adelaide, said, "In principle, gas-fired power is more efficient but when you consider the full range of effects of burning coal, there are other problems that it creates. "Using more gas would reduce CO₂ emissions but it would also lead to more methane being released, and that has a much higher global warming potential", he said.

The climate model used in the study is calibrated to models used by the CSIRO and the Bureau of Meteorology. The study has implications for Australia because the Federal Government's carbon tax is aimed in part at replacing the nation's coal-fired plants with gas, as well as making renewable energy cheaper compared to fossil fuels. Whether the research is taken into account would depend on whether it is accepted as part of the next assessment produced by the Intergovernmental Panel on Climate Change in 2014.

Methane is 20 to 30 times as potent a greenhouse gas as CO₂. Professor Wigley's paper, Coal to Gas: The Influence of Methane Leakage, found that if the amount of methane leaking from gas wells and pipelines around the world could be held below 2.5% of the total amount of methane used, the world's temperature would still rise, but increase about a 10th of a degree more slowly by the year 2100. If the leakage rate was higher, it would take even longer to start slowing temperature increases.

If the amount of methane that leaked was reduced to zero, the rate at which the world was warming up would slow slightly from about 2050. The Australian Petroleum Production & Exploration Association says the rate of leaks from coal seam gas wells in Australia is negligible, and all "fugitive" emissions are accounted for when gas companies report their emissions to the Department of Climate Change and Energy Efficiency. Power stations in Queensland that run solely on coal seam gas produce greenhouse emissions that are up to 73% less per MW of electricity than Hazelwood power station in Victoria, which burns brown coal, the association said.