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This story was originally published by the HuffPost. It appears here as part of the Climate Desk collaboration. The world is rapidly running out of time to scale back greenhouse gas emissions, dimming hopes of keeping global warming within 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels, beyond which catastrophic planetary changes are forecast.

That assessment comes from a sobering new report issued by the Intergovernmental Panel on Climate Change, or IPCC, the leading United Nations consortium of researchers studying the speed and scope of human-caused temperature rise.

“This is one of the most important reports ever produced by the IPCC, and certainly one of the most needed,” Hoesung Lee, the chair of the body, said at a press conference in South Korea on Monday. “Climate change is already affecting people, livelihood and ecosystems all around the world.” “This is one of the most important reports ever produced by the IPCC, and certainly one of the most needed.”

He continued: “Every bit of warming matters.”

The report—authored by 91 researchers and editors from 40 countries citing more than 6,000 scientific references and released Sunday night following a summit in Incheon, South Korea—details how difficult it will be to keep the planet from warming beyond the 1.5-degree target, considered the aspirational goal of the 2015 Paris climate accord.

To meet that target, the world would need to aggressively phase out fossil fuels to meet net-zero emissions by mid-century, and remove carbon dioxide and other heat-trapping gases out of the atmosphere from then on, according to the IPCC. More immediately, emissions would have to drop by about 45 percent below 2010 levels by 2030.

At 1.5 degrees of warming, small islands and major coastal metropoles like New York City, Mumbai and Jakarta risk disastrous flooding without costly sea barriers.

Yet carbon emissions began growing again last year after a three-year plateau as fossil-fuel emissions hit an all-time high. Emissions have quadrupled since 1960, and globally the last four years have been the warmest four on record, according to an international report released in August.

“I see so little evidence that 1.5 is achievable that I think that the main impact of a focus on 1.5 will be to demoralize people,” Andrew Dessler, a climate scientist at Texas A&M University, said in an email Sunday.