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Greenhouse gases from Coal Seam Gas – important, underestimated

CSG worries hinge on timing of climate change, ABC News 10 Dec 12 by Wendy Carlisle for Background Briefing An expert in public policy says the debate over whether coal seam gas is cleaner than coal depends on the timeframe used to measure emissions.

According to a scientific paper by US academic Nathan Hultman, coal seam gas is 56 per cent cleaner than coal over a 100-year time frame, but when compared to coal over 20 years it is less than 20 per cent cleaner. Professor Hultman, from the school of public policy at the University of Maryland, says using the “most extreme assumptions”, coal seam gas is actually dirtier than coal over a 20-year time frame.

He told Radio National’s Background Briefing the choice of timescale was a “value judgment” and “depended on when you thought the real problem of climate change was going to bite”.

“The reason you would be worried about methane in particular over a 20-year time horizon is if you are thinking we are on the verge of a kind of tipping point in climate change right now,” he said.

“If you really think right now we are very close to melting the ice caps or pushing the climate from a moderately steady state into a kind of bad outcome where you’ve got runaway climate change.”

According to the Intergovernmental Panel on Climate Change, the global warming impact of greenhouse gases can be measured across three different times frames: 20 years, 100 years or 500 years.

Each is valid and chosen by atmospheric scientists depending on what scientific point they wish to highlight.

Coal seam gas is mostly methane – a powerful greenhouse gas that has a relatively short life span.
This means that over a 20-year time frame, coal seam gas has a much higher global warming impact than if it is measured over 100 years. http://www.abc.net.au/news/2012-12-09/background-briefing-coal-seam-gas/4416808

December 10, 2012 - Posted by Christina Macpherson | Uncategorized