Australia might be cited as a classic illustration of the adverse impact of global warming. Still the eventual temperature rise might be less severe than feared, researchers say.
It is not very comforting though. For the increases in the extreme temperatures predicted by the more credible assessments are still extremely high. Such increases would generate heat waves much worse than the recent one that hit south-eastern Australia.
The tempered message was delivered by a team from the by University of New South Wales (UNSW). It compared the climate models used by the Intergovernmental Panel on Climate Change (IPCC) and tested their accuracy against actual climate observations to select the strongest and weakest ones. The findings have been published in Geophysical Research Letters.
The researchers looked specifically at rare extreme events - those that occur on average once each 20 years - because heat wave conditions can dramatically affect biological, physical or human systems and are of most concern for planners and policy makers.
They found that the best-performing climate models simulated smaller rises in the temperature extremes compared with the models that performed poorly.
The least accurate models were found to bias the average of all IPCC models towards higher temperature increases of about 3 to 5 degrees Celsius over most of the continent by the end of the century. When those weak models were removed from the average, the predicted increase was 2 to 3 C (although in some regions the increase could be smaller or greater).
Recent heat waves - such as the recent ones in Adelaide or Melbourne - have been "phenomenally hot," notes one of the authors of the study, Professor Andy Pitman, co-director of the UNSW Climate Change Research Centre.
Professor Pitman points out that Melbourne's record maximum temperature reached 46.4 C during the heatwave and power systems failed and trains were stopped by warped rails. At Hopetoun Airport in Victoria, a new record maximum temperature for the State was recorded on 7 February at 48.8 C.
"Even with our revised projections, adding two or three degrees to 47 C days is not a prospect I think anyone would like to experience," he says. "The lower figures are not as bad as 3 to 5 C, but they're still very bad and emphasise the need to aggressively cut greenhouse gases on a global scale.
"While we have not determined if this result is common to other continents, our results were similar over temperate, sub-tropical and tropical regions so we think its likely that our results can likely be extrapolated elsewhere."
The study was authored by Sarah Perkins, Professor Pitman - both of the UNSW Climate Change Research Centre- and Dr Scott Sisson, UNSW School of Mathematics and Statistics.