Wednesday, November 6, 2013

Greenhouse gases rise to record, will drive climate change, world body says

Peter Hannam
The Age,  November 7, 2013 

Greenhouse gases in the atmosphere are rising at an accelerating pace to record levels, a trend that will drive climate change and endanger future generations, according to the World Meteorological Organisation Greenhouse Gas Bulletin No. 9 (pdf).

Carbon dioxide, the most important greenhouse gas linked to fossil fuel burning and deforestation, rose by an average of 2.2 parts per million (ppm) in 2012 to 393.1. That increase compared with 1.5 ppm in the 1990s and 2 ppm in the past decade, and brings atmospheric levels to 41 per cent more than pre-industrial times, the WMO said in its annual Greenhouse Gas Bulletin.

Methane emissions, 60 per cent of which come from human activities such as cattle breeding and fossil fuel extraction, also reached a new high at 1819 parts per billion (ppb) in 2012, rising by 6 ppb. The gas resumed its increase after a pause between 1999 and 2006.

Nitrous oxide, another important gas with almost 300 times the impact on climate as carbon dioxide and is linked to fertiliser use among other sources, rose 0.9 ppb to 325.1 ppb, quickening from the 0.8 ppb average increase over the previous decade.

Between 1990 and 2012 there was a 32 per cent increase in radiative forcing - the warming effect on our climate - because of the increase in these long-lived greenhouse gases, the WMO said.

Michael Raupach, a team leader in CSIRO's Marine and Atmospheric Research division, said the rise in atmospheric temperatures from the additional greenhouse gases had been temporarily limited by the oceans absorbing much of the extra heat trapped by those gases.

That pause, though, will end and "we'll see a return to significant rates of warming," he said.  

While reducing carbon emissions won't stop the build-up of heat in the earth's biosphere, reductions now reduce the magnitude of the future task.

"The reduction in emissions over the [near term] is absolutely essential," Dr Raupach said. Failure to do so will mean the size of future cuts required will "become completely impossible if we are to avoid any reasonable definition of dangerous climate change."

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