Burning all the world's known fossil fuels would result in the release of the equivalent of 5 trillion tonnes of carbon dioxide and drive global temperatures 8 degrees warmer than pre-industrial levels by 2300, a report by Canadian researchers has found.
The study, published on Tuesday in Nature Climate Change, extended models used for the Intergovernmental Panel on Climate Change and found impacts that were "considerably larger" than previously indicated.
For instance, by 2300, global temperatures would range from 6.4-9.5 degrees warmer than pre-industrial times with a mean warming of 8.2 degrees. Arctic regions warm by as much as 19.5 degrees.
Rainfall changes would include increases of as much as fourfold in tropical areas, while more-temperate areas – such as parts of Australia, the Mediterranean and the Amazon – could have rainfall halved, the researchers led by Katarzyna Tokarska, at University of Victoria, found.
"Such climate changes, if realised, would have extremely profound impacts on ecosystems, human health, agriculture, economies and other sectors," the paper says.
Previous models were either over-simplified and underestimated the warming potential of warming or ran out to as far as the year 3000, the paper said.
Not only would thawing permafrost in Arctic regions release huge amounts of greenhouse gases, existing carbon sinks –such as oceans and the tropics – would take in less carbon dioxide, leaving more of it the atmosphere, he said.
"If we continue to ultimately burn all that we know to be in our fossil fuel reserves, we will literally cook the planet and we'll transform regions dramatically," Dr Canadell said.
"We all know we need to wind down [fossil fuel use] very, very quickly if we are to reach 2-degrees stabilisation of the climate", he said.
He said the latest figures show this year is running about 1.1 degrees above pre-industrial times, with many impacts already evident.
"We are not that far from 100 per cent bleaching [of the Great Barrier Reef]," he said. "Imagine this year and last year with an El Nino at 2 degrees – anything that is sensitive to that, from agriculture to the natural world, can be instantly obliterated."
Matt England, a climate expert at the ARC Centre of Excellence for Climate System Science, said the paper was "very important" as a reminder that economies had to change course.
"I see no trend from our addiction to fossil fuels," Professor England said.
"It is worrying to see exploration for more fossil fuels is ongoing," he said, noting that the melting Arctic sea ice was enabling easier prospecting for oil and gas.
Analysis by the Carbon Brief of the latest emissions data last week week found the world would burn through its carbon budget within five years, which would provide at least a two-thirds chance of keeping warming to within 1.5 degrees of pre-industrial levels. (See chart below.)
Last year, the Climate Council estimated that as much as 90 per cent of Australia's remaining fossil fuel reserves would have to remain in the ground, assuming the country did its bit to keep warming to within 2 degrees.