In a strategic retreat in the fight against climate change, the United Nations has acknowledged that Earth has lost its chance to prevent some of the worst of global warming's harms. Officials say the world must now figure out how to get temperatures below the danger zone and back to safety.
The planet will soon exceed the safe temperature threshold agreed upon in the 2015 Paris climate accord because of warming from the burning of coal, oil and gas, according to a bleak first-of-its-kind report issued by the United Nations Environment Programme Wednesday.
Instead of giving up, scientists and UN officials recommend trying to limit excessive warming and then bring the temperature back down to the agreed-upon threshold. But it still will mean decades of increased weather-related disasters, rising seas, extinctions and melting ice and glaciers.
"Humanity is speeding past the limit to avoid climate catastrophe," United Nations Secretary-General António Guterres said.
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After a period of over-the-limit warming, the new strategy envisions getting back below the limit by ending fossil fuel use and developing some way to suck industries' carbon dioxide out of the air.
"It's a reality check. We have to live with this warmer world," said report co-author Richard Betts, a climate scientist at the University of Exeter. "But there's still a lot we can do to limit warming."
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After the Paris climate accord, the United Nations ordered its climate science arm to study different warming limits. Scientists generally accepted a limit of 1.5 C above mid-19th century temperatures, after finding dramatic impacts that affect people and the planet at 2 C but not at 1.5 C.
The world is now at 1.4 C above pre-industrial levels, some scientists have calculated. The measure is based on a 20-year average, rather than a single year's temperatures.
Despite experts saying there's no way to limit warming to 1.5 C, UN officials long maintained the 1.5 C window was still open. Wednesday's report finally admitted that the world will cross the 1.5 threshold "in the next few years."
The report said the most optimistic scenario has warming peaking at 1.8 C around mid-century if countries pursue ambitious climate goals, but that governments' current policies should push temperatures to 2.6 C above pre-industrial levels by 2100.
The UN said it wants policymakers to "prepare for and navigate a future'' in which the globe crosses that limit and then corrects course and cools temperatures.
The report envisions that after exceeding 1.5 C, global temperatures will follow a hump-shaped path of more warming, peak, then gradually cool to below the 1.5 C mark, ideally by the end of the century. The report and experts call it "overshoot."
