A CSIRO scientist has told a Senate inquiry it is imperative to begin phasing out coal burning in order to avoid dangerous climate change.
No coal-fired power plants should be built, and existing plants must shut within 20 years, if the world is to keep atmospheric carbon dioxide at a less dangerous level, the climatologist James Risbey said.
Yesterday Dr Risbey joined other CSIRO scientists who have spoken out personally to the Senate committee on climate policy's inquiry after the CSIRO decided against making a submission.
He said the Rudd Government's targets of reducing carbon dioxide levels by at least 5 per cent of 2000 levels by 2020 and 60 per cent by 2050 were not tough enough to avoid dangerous climate change.
"In fact, they yield a high likelihood of triggering irreversible changes in the climate system," he said at the committee's hearings in Hobart. "Such likelihoods can be greatly reduced with far more stringent emissions reductions. However, further delay makes safer concentration targets unattainable and begins to lock in dangerous climate change."
The committee was told that at current levels of greenhouse gas growth, the world risked an irreversible collapse in the Greenland and West Antarctic ice sheets, contributing roughly seven and five metres each to global sea level rise.
Acidification of the oceans, release of stored methane and breakdown of snowmelt would also affect food webs and the global population.
"While we cannot give a precise temperature at which each of these processes would occur, the threshold is thought to be in the vicinity of about two degrees in each case," Dr Risbey said.
But Australia's proposed Carbon Pollution Reduction Scheme, if applied by all countries, would mean a 50 to 90 per cent chance of exceeding the threshold.
"In other words, this is Russian roulette with the climate system, with most of the chambers loaded," he said.