Three Years Left To Limit Warming To 1.5C, Leading Scientists Warn

An anonymous reader quotes a report from the BBC: The Earth could be doomed to breach the symbolic 1.5C warming limit in as little as three years at current levels of carbon dioxide emissions. That's the stark warning from more than 60 of the world's leading climate scientists in the most up-to-date assessment of the state of global warming. At the beginning of 2020, scientists estimated that humanity could only emit 500 billion more tonnes of carbon dioxide (CO2) -- the most important planet-warming gas -- for a 50% chance of keeping warming to 1.5C. But by the start of 2025 this so-called 'carbon budget' had shrunk to 130 billion tonnes, according to the new study.

That reduction is largely due to continued record emissions of CO2 and other planet-warming greenhouse gases like methane, but also improvements in the scientific estimates. If global CO2 emissions stay at their current highs of about 40 billion tonnes a year, 130 billion tonnes gives the world roughly three years until that carbon budget is exhausted. This could commit the world to breaching the target set by the Paris agreement, the researchers say, though the planet would probably not pass 1.5C of human-caused warming until a few years later.

Last year was the first on record when global average air temperatures were more than 1.5C above those of the late 1800s. A single 12-month period isn't considered a breach of the Paris agreement, however, with the record heat of 2024 given an extra boost by natural weather patterns. But human-caused warming was by far the main reason for last year's high temperatures, reaching 1.36C above pre-industrial levels, the researchers estimate. This current rate of warming is about 0.27C per decade -- much faster than anything in the geological record. And if emissions stay high, the planet is on track to reach 1.5C of warming on that metric around the year 2030. After this point, long-term warming could, in theory, be brought back down by sucking large quantities of CO2 back out of the atmosphere. But the authors urge caution on relying on these ambitious technologies serving as a get-out-of-jail card. 'For larger exceedance [of 1.5C], it becomes less likely that removals [of CO2] will perfectly reverse the warming caused by today's emissions,' warned Joeri Rogelj, professor of climate science and policy at Imperial College London.

'Reductions in emissions over the next decade can critically change the rate of warming,' he added. 'Every fraction of warming that we can avoid will result in less harm and less suffering of particularly poor and vulnerable populations and less challenges for our societies to live the lives that we desire.'

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