OSLO • Global warming is on track to breach the toughest limit set in the Paris climate agreement by the middle of this century unless governments make unprecedented economic shifts from fossil fuels, a draft United Nations report said.
The draft of a report due for publication in October said governments will also have to start sucking carbon dioxide from the air to achieve the ambition of limiting temperatures to 1.5 deg C above pre-industrial times.
"There is very high risk that... global warming will exceed 1.5 deg C above pre-industrial levels," the UN panel of experts wrote, based on the current pace of warming and current national plans to limit greenhouse gas emissions.
There were no historic precedents for the scale of changes required in energy use, to shift from fossil fuels to renewable energies, and in reforms ranging from agriculture to industry to stay below the 1.5 deg C limit, it said.
The draft, by the UN's Intergovernmental Panel on Climate Change (IPCC) of leading scientists and obtained by Reuters, says average surface temperatures are about 1 deg C above pre-industrial times and that average temperatures are on track to reach 1.5 deg C by the 2040s.
Curbing warming to 1.5 deg C would help limit heat extremes, droughts and floods, more migration of people and even risks of conflict compared with higher rates of warming, according to the draft summary for policymakers.
But a 1.5 deg C rise might not be enough to protect many coral reefs, already suffering from higher ocean temperatures, and ice stored in Greenland and West Antarctica, whose melt is raising sea levels.
At a 2015 summit in Paris, almost 200 nations set a goal of limiting a rise in the world's average surface temperatures to "well below" 2 deg C above pre-industrial times while "pursuing efforts" for the far tougher 1.5 deg C ceiling.
Limit to number of tonnes of greenhouse gases humanity could emit to give a better than 50 per cent chance of keeping warming to 1.5 deg C - roughly 12 to 16 years at current rates of emissions.
They commissioned the IPCC report to map the risks of each goal. The 1.5 deg C limit is favoured especially by developing countries most at risk from disruptions to food and water supplies.
The current draft was sent out for comments from governments and other experts this week. IPCC spokesman Jonathan Lynn said the text was a work in progress not intended for publication. "The text can change substantially," he said.
United States President Donald Trump, who doubts climate change is man-made, plans to pull out of the Paris Agreement and instead focus on US fossil fuels. But on Wednesday, he said the US could "conceivably" return to the accord, although he stopped short of signalling any move in that direction.
The draft said that renewable energies such as solar and wind power would have to become the dominant form of primary energy by 2050 to achieve the 1.5 deg C goal. "Coal would be phased out rapidly in most 1.5 deg C pathways," it said.
The draft estimated that humanity could emit just 580 billion tonnes of greenhouse gases to give a better than 50 per cent chance of limiting warming to 1.5 deg C - roughly 12 to 16 years at current rates of emissions.
REUTERS, AGENCE FRANCE-PRESSE