Climate change: 42% chance of breaching 1.5°C goal even if all carbon emissions cease

Even a completely unrealistic scenario in which all carbon emissions end overnight would see a 42 per cent chance of exceeding the goal of limiting global warming to 1.5°C

By Adam Vaughan

Humanity has pumped so much carbon dioxide into the atmosphere that there is now a 42 per cent chance of the world breaching its 1.5°C climate change goal even if global emissions ceased overnight, researchers have estimated.

Countries resumed United Nations climate negotiations today, to discuss stronger emissions cuts with the aim of meeting the Paris Agreement’s pledge to hold temperature rises since pre-industrial times to 1.5°C. But as negotiators meet in Bonn, Germany, a new analysis has found that regardless of the short term direction that global emissions take, by 2032, the chance of busting the 1.5°C target will rise to 66 per cent.

Michelle Dvorak at the University of Washington in Seattle and her colleagues modelled what level temperatures would peak in the future if emissions were to abruptly halt. They found that historical emissions have already left us with a 42 per cent probability of exceeding 1.5°C, an increase on a  less than 33 per cent chance just four years ago.

However, the team shows that prospects for meeting the Paris Agreement’s weaker backstop of 2°C is still well within reach, provided emissions are cut rapidly. The researchers put the probability of exceeding 2°C at just 2 per cent if we stopped emitting today.

That figure will reach greater than 66 per cent if emissions follow a medium or high path in the future, and not until some point between 2043 and 2057. The world is currently roughly on track for a medium emissions pathway, but further climate action is expected to bring that down.

“They are looking at geophysical commitments,” says Glen Peters at the CICERO Center for International Climate Research in Oslo, Norway, meaning the absolute minimum of warming given the CO₂ already committed to the atmosphere.  “In all reality, we will not get emissions to zero overnight, so that basically means we are already committed to 1.5°C.”

The study comes as non-profit organisation Climate Action Tracker found that countries’ progress on their emissions-cutting plans has “stalled” since COP26, the major UN climate summit last November. The group said the inaction “goes against” the promise governments made at COP26, to bolster their plans in 2022.

Data published on 3 June revealed that atmospheric concentrations of CO₂ reached a monthly average of more than 420 parts per million in May, 50 per cent above pre-industrial levels.

Journal reference: Nature Climate Change, DOI: 10.1038/s41558-022-01372-y

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