By Bronwyn Herbert
ABC News Online, 11 March 2011
The Federal Government's key climate adviser says the scientific case for climate change has been strengthened. The immediate implication is that avoiding high risks will require large changes in trajectories at an early date.
On Thursday, Ross Garnaut released the fifth update to his 2008 report on climate change - specifically tackling climate science (available for download here).
Professor Garnaut says new science since the 2007 International Panel on Climate Change research has strengthened the position that the Earth is warming and that human emissions of greenhouse gases are the main cause.
He also released specific data on temperature, sea level rises and extreme events from recent years.
"On the measurable phenomena, it does seem that certainly there's been no evidence of overstatement," he said.
"And it does seem to be a number of points of understatement, and I call that an awful reality because it would be much better if [the] opposite were true.
"It would be much better if the evidence was showing the earlier signs had overstated things."
Professor Garnaut says the world should have a target for cutting emissions.
"The conclusion of the review is that it's in Australia's national interest for the world to succeed in holding emissions to 450 parts per million," he said.
"That's much better than the world being moderately successful at mitigation and holding things to 550."
The update comes as the political debate on the Government's proposed carbon tax heats up.
This week's Newspoll shows a majority of people are against a price on carbon.
Those surveyed were responding to a question on whether they would personally be in favour or against paying more for energy or petrol if it would help slow global warming.
Professor Garnaut says there has been a rise in the number of opinion polls and surveys on climate change.
He says it is difficult to tie down their statistical significance, but it is clear public confidence has diminished.
"It's an important question, why it seems that in Australia, the United States and some European countries confidence in the science has diminished," he said.
"I can't hold myself as a particular authority on this... but one must presume that as an issue moves from something of purely scientific interest into the subject of political debate and dispute, there's a whole lot of communications come into play that aren't actually about the science and that will affect people's perception of the science."
A CSIRO review found a majority of Australians, between 63 and 83 per cent, believe the climate is changing.
But across the surveys only 50 per cent agreed human activity was driving climate change.
"If you take our mainstream media, it will often seek to provide some balance between people who base their views on mainstream science and people who don't," he said.
"That's a very strange sort of balance; it's a balance of numbers of words and not a balance of scientific authority," Professor Garnaut said.
Professor Garnaut's next paper will deal with the contentious issue of carbon pricing.
The final report will be delivered to the Government by the end of May.