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“It’s not that the fight against climate change will be lost after six years, but I think probably if we’re not already on a strong downward trajectory, it’ll be too late to fight for that 1.5 degree limit,” said study lead author Robin Lamboll, an Imperial College of London climate scientist. A 2021 United Nations Intergovernmental Panel on Climate Change report gave a budget of 500 billion metric tons pointed to a mid 2032 date for locking in 1.5 degrees, Lamboll said. An update by many IPCC authors this June came up with a carbon budget the same as Lamboll’s team, but Lamboll’s analysis is more detailed, said IPCC report co-chair and climate scientist Valerie Masson-Delmotte. The biggest change from the 2021 report to this year’s studies is that new research show bigger reductions in aerosol emissions — which come from wildfires, sea salt spray, volcanoes and burning fossil fuels — that lead to sooty air that cools the planet a tad, covering up the bigger greenhouse gas effect. As the world cleans up its carbon-emitting emissions it is simultaneously reducing the cooling aerosols too and the study takes that more into account, as do changes to computer simulations, Lamboll said. Even though the carbon budget looks to run out early in the year 2029, that doesn’t mean the world will instantly hit 1.5 degrees warmer than pre-industrial times. The actual temperature change could happen a bit earlier or as much as a decade or two later, but it will happen once the budget runs out, Lamboll said. People should not misinterpret running out of the budget for 1.5 degrees as the only time left to stop global warming, the authors said. Their study said the carbon budget with a 50% chance to keep warming below 2 degrees Celsius (3.6 degrees Fahrenheit) is 1220 billion metric tons, which is about 30 years.
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