Original URL: http://www.theregister.co.uk/2013/05/29/warming_6degc_unlikely_2degc_nearly_certain/

Warming: 6°C unlikely, 2°C nearly certain

'Waiting for certainty will fail as a strategy' say Oz boffins

By Richard Chirgwin

Posted in Science, 29th May 2013 01:58 GMT

Under “business as usual” global warming will almost certainly exceed 2°C by 2100, but the high-end extreme range of warming of 6°C is unlikely to occur.

That “good news, bad news” scenario comes from work conducted by Dr Roger Bodman from Victoria University, with Professors David Karoly and Peter Rayner from the University of Melbourne.

The researchers say that most of the current uncertainties in climate prediction arise from single sources. These include climate sensitivity, the future behaviour of the carbon cycle, and the cooling effect of aerosols. These make up for 63 percent of the predictive uncertainty of climate models, with the remaining 37 percent driven by combinations of sources.

The work, published in Nature Climate Change, identifies the carbon cycle as the second-most important uncertainty factor for any given emission scenario. Reducing the uncertainties involved with modelling the carbon cycle, they say, provides the more certain predictions for the future.

Dr Bodman emphasises that predictions with less uncertainty still don't count as “certain”. “Waiting for certainty will fail as a strategy," he said. "Some uncertainty will always remain, meaning that we need to manage the risks of warming with the knowledge we have." ®