Temperatures are on course to rise at least 4 degrees by the end of the century, according to research that finds earlier climate models projecting smaller increases are likely to be wrong.
The research, by a team led by the University of NSW, says a 4-degree rise in temperature would be potentially catastrophic for agriculture in warm regions of the world, including Australia.
Forecasts in many climate models for lower temperature rises were based on assumptions that clouds might help limit temperature increases.
But the team claims to have found the key to predicting cloud behaviour, and forecasts that clouds will not be nearly as helpful as thought in many models.
Current models estimate a doubling of carbon dioxide in the atmosphere – a level that may be reached by mid-century – will result in temperature rises of between 1.5 degrees and 5 degrees. Instead, the likely range will be 3-5 degrees for twice the amount of C02, the study found.
The publication of the research comes as the top business adviser to Prime Minister Tony Abbott has again caused controversy with comments about the ''delusion'' of global warming and an assertion that climate change policy has destroyed Australia's manufacturing sector and competitiveness.
In an opinion piece in The Australian newspaper, Maurice Newman, Mr Abbott's pick as head of his Business Advisory Council, said high energy costs caused by the carbon tax and the renewable energy target, introduced under the Howard government, had eroded competitiveness.
Under Labor and the Greens, Australia had been taken hostage by ''climate change madness'', Mr Newman wrote.
The research, published on Wednesday in the respected journal Nature, comes as Australia ends its hottest year in more than a century of data collection, with 2013 eclipsing the record set in 2005.
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