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The world may be in breach of the 1.5C level of long term global warming set down under the Paris agreement sooner than previous studies have shown, according to two new scientific papers.
The first paper, by researchers in Germany and Austria, found that without stringent cuts in emissions the world was “most probably” now within the two decades where a breach of the Paris agreement would occur.
“Cutting emissions has never been more important, and it can substantially lower the probability of reaching the 1.5C limit soon after 2024,” said lead author Emanuele Bevacqua, from the Helmholtz Centre for Environmental Research.
Almost 200 countries agreed to limit the global temperature rise to well below 2C and ideally to 1.5C above pre-industrial levels under the Paris accord signed in 2015. This is measured over a period of more than two decades.
When the agreement was signed, the world was projected to reach the 1.5C threshold by March 2045.
Since then, the leading scientific body, the Intergovernmental Panel on Climate Change, has modelled a median expectation for it to be passed around 2031, while the European earth agency put the potential breach of the benchmark in 2034 when it made its forecast about a year ago.
But as greenhouse gas emissions continue to rise and record annual temperatures increase experts have questioned whether it is still feasible to regard a limit of warming within 1.5C as achievable.
The latest two studies, published in the journal Nature on Monday, both said the lower limit of the accord looked increasingly out of reach without urgent climate action.
The papers examined what the exceptionally hot year in 2024 — when the global average temperature surpassed 1.5C for the first time annually — meant for the limiting the long term global temperature.
The second study by Alex Cannon, a research scientist at the Environment and Climate Change Canada government department, said 2024’s heat signalled a sooner-than-expected breach of the Paris accord.
Based on the modelling, the research found that if 18 consecutive months of temperatures at or above 1.5C of warming occur, continued warming is virtually certain under a so-called “middle of the road” scenario, where social, economic and technological trends do not shift markedly.
Last week, the EU’s Copernicus climate change service said the temperature in January was 1.75C above the pre-industrial levels, making it the 18th month out of the last 19 for which the global average surface air temperature was more than 1.5C above the 1850-1900 reference period.
Piers Forster, professor of physical climate change at the University of Leeds and one of the authors of the IPCC report, said Cannon’s findings for crossing 1.5C was “slightly earlier” than previous estimates “but well within its uncertainty range”.
He said the world was now at the “start of a period of temperatures above 1.5C of warming, but we still may get the odd slightly cooler year”, which might “give a sense of complacency that 1.5C of warming is not too bad”.
“However, we have not felt all the impacts of a 1.5C warmer world. The longer we stay at or above 1.5C, we can expect more extreme weather, biodiversity and ice sheet loss,” he warned.
Without urgent action on emissions “we will not only breech the lower level of the Paris long term temperature goal, but the entire goal will sink under rising seas,” he said.
Scientists say every fraction of a degree matters, with a big difference in outcomes for the world between 1.5C and 2C of warming including loss of species, coral bleaching and the area of the world exposed to extreme heat.
Tim Lenton, another IPCC author, said the two papers tallied with his “expectation that we are now committed to exceeding 1.5C and that mean warming of 1.5C will be centred around 2030”.
He added: “The question now is how much we can limit the overshoot of 1.5C and all the associated escalating damages.”
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