Warming uncertain says CSIRO scientist
The CSIRO is a major scientific research organization funded by the Australian government
Researchers from the CSIRO and the University of Melbourne analysed the predictions of 23 currently available global climate models using data from the Coupled Model Intercomparison Project, a project that gathers data from around the world to make predictions on changes in world climate.
A statistical tool called a 'probability distribution model' was applied to the projected changes predicted by the models to find what changes would occur at certain levels. These probability distribution functions were scaled to match scenarios of global warming for 2030 and 2070.
Climate predictions then and now
Previous projections by the CSIRO and the Bureau of Meteorology in 2007 predicted a temperature increase of at least 1 degree Celsius by 2030. “If emissions are low, we anticipate warming of between 1.5 degree and 2.5 degrees by 2070, with a best estimate of 1.8 degrees,” Whetton said in 2007. “Under a high emission scenario, the best estimate is 3.4 degrees Celsius with a range between 2.2 to 5.0.”
The 2007 report also predicted the effect of increasing levels of greenhouse gases on rainfall, showing decreases in overall and seasonal rainfall across Australia in the decades to come.
The new study gives a more solid prediction to the effects of a global climatic shift. If global temperatures increased by 4 degrees Celsius or more, it would result in temperature increases of between 3 degrees and 5 degrees for coastal areas and 4 degrees to 6 degrees for inland Australia, the report shows.
In addition, global climate shifts would affect precipitation patterns, with snow cover falling to zero in most regions across the Australian Alps. More notably, the annual rainfall over southern Australia, particularly in winter and spring, would decrease by up to 50%.
"Unlike anything experienced before"
The combined decrease in rainfall with rising evaporation levels of between 5% and 20%, would lead to droughts occurring up five times more often in the southern regions of Australia, the study said.
"Rapid global warming of 4 degrees Celsius would be unlike anything experienced before by modern human societies - presenting us with huge challenges in our ability to adapt," Whetton said.
Steven Sherwood, an atmospheric physicist and co-director of the Climate Change Research Centre at the University of New South Wales in Sydney, said that while the report, "follows a fairly standard methodology" in summarising the predictions of climate models, the estimates "must be taken with a grain of salt" because of the variability between the 23 models. "They don't all predict the same outcome, so a large range can sometimes appear - but this probably represents the best we can do at the moment," he said.
Sherwood continued, "Of course there is no guarantee that the actual outcome will even be within this range, all the models could be off. But if the models are wrong, it is just as likely to be in the direction of underestimating change rather than overestimating it. "Either way, it's better to be safe than sorry and we need to reduce greenhouse emissions now while we still can before it's too late."