Scientists have warned our planet has three years less than previously thought to avoid a long-feared climate change landmark that will bring about more catastrophic weather, destroy most coral reefs, and cause significant water shortages.
Warming of 1.5 degrees compared to pre-industrial times has been earmarked as a crucial goal in the fight against climate change, including in the 2015 Paris Agreement.
But according to a new study published in Nature Climate Change, that will be unavoidable by early 2029 – little more than five years from now – if global emissions from fossil fuels continue at their current rate.
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The authors of the study calculated what's known as the remaining carbon budget (RCB) for 1.5 degrees – the amount of carbon that can be released into the atmosphere for there to be a 50 per cent chance of limiting warming to that temperature.
In 2021, a United Nations report estimated the RCB was about 500 billion metric tonnes – enough to last until 2032.
The new study argues the RCB was just 250 billion metric tonnes at the start of the year.
With the planet emitting about 40 billion per year, warming of 1.5 degrees will be locked in by early 2029.
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However, with global emissions still rising – although they appear to be starting to plateau – the mark may be reached even quicker.
The reason for the smaller RCB is the world has been removing smoky aerosol pollutants in the atmosphere.
While a positive step, those pollutants slightly cool Earth and mask the effects of burning fossil fuels, so the planet warms marginally faster without them.
Regardless, the planet is preciously short of time to avoid hitting 1.5 degrees of warming.
Once Earth reaches that measure, the risk of extreme weather and other catastrophes increases, as the world will likely lose most of its coral reefs, a key ice sheet could kick into an irreversible melt, and water shortages, heat waves and death from extreme weather dramatically increase, according to an earlier United Nations scientific report.
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"We have got to the stage where the 1.5 Celsius carbon budget is so small that it's almost losing meaning," climate scientist Glen Peters of the Norwegian CICERO climate institute, who wasn't part of the research, said.
"If your face is about to slam in the wall at 100 miles per hour, it is sort of irrelevant if your nose is currently one millimetre or two millimetres from the wall… we are still heading in the wrong direction at 100 miles per hour."
Climate scientist Bill Hare of the Climate Action Tracker said "breaching the 1.5-degree limit does not push the world over a cliff at that point, but it is very much an inflection point in increasing risk of catastrophic changes".
Even though the carbon budget looks set to run out in early 2029, that doesn't mean the world will instantly hit 1.5 degrees of warming – that could happen a bit earlier or as much as a decade or two later, but it will happen once the budget runs out, study lead Robin Lamboll said.
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Despite 1.5 degrees of warming looking unavoidable, the researchers said it was critical for the planet to quickly reduce emissions so higher and even more catastrophic thresholds are avoided.
The study said the carbon budget with a 50 per cent chance to keep warming below 2 degrees is 1220 billion metric tons, which is about 30 years.
There are about 23 and 12 years left for a 66 and 90 per cent chance of avoiding that mark respectively, the study says.
"We don't want this to be interpreted as six years to save the planet," study co-author Christopher Smith, a University of Leeds climate scientist, said.
"If we are able to limit warming to 1.6 degrees or 1.65 degrees or 1.7 degrees, that's a lot better than 2 degrees. We still need to fight for every tenth of a degree."
– With Associated Press
