But he said it was positive news that the report showed the pathways to 2 degrees of warming were open, achievable and readily affordable. This would mean having emissions peak in 2025 and reduce by a quarter by 2030.

He said the impacts of 2 degrees were far worse than 1.5 degrees, but that until recent changes in policy around the world and reductions in the cost of renewable technologies, that target appeared out of reach too. “The reference point here is what is realistically achievable,” he said.

The report showed that policies already adopted were having a significant impact on emissions, but also in protecting ecosystems while helping create new jobs.

“[The report] shows that a one-quarter reduction in global emissions would be possible and costs below US$20 dollars ($27) per tonne. So now we’re talking costs that are far below for example, the current European Union emissions trading price,” he said.

Limiting warming to about 1.5 degrees required global greenhouse gas emissions to peak before 2025 at the latest, and be reduced by 43 per cent by 2030; at the same time, methane would also need to be reduced by about a third, the IPCC said in a statement.

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“Even if we do this, it is almost inevitable that we will temporarily exceed this temperature threshold but could return to below it by the end of the century.”

“It’s now or never, if we want to limit global warming to 1.5 degrees,” said Jim Skea, co-chair of the IPCC working group that wrote the report. “Without immediate and deep emissions reductions across all sectors, it will be impossible. ”

The report is the third part of a series that make up the IPCC sixth assessment of climate change. The first part, published last year, was a scientific assessment of the speed of the change to the climate caused by greenhouse gas emissions. The second part, published last month, outlined impacts on the planet and potential adaptation strategies.

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The third instalment was the most contentious as it outlined what actions world governments need to take to prevent the warming from getting far worse. The release was delayed as officials representing world governments engaged in line-by-line negotiations over the final text. It is understood that the potential role of carbon capture and storage technologies were among the contentious issues.

US President Joe Biden’s climate envoy John Kerry said the report was a “defining moment” for the world, showing that we were falling short, but also that we had the tools to succeed.

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