The world is likely to cross the 1.5 degrees Celsius warming threshold within years, but governments can still limit the damage and eventually bring temperatures back down, the U.N. Environment Programme said on Wednesday.
In its first dedicated assessment of how to respond to an overshoot of the Paris Agreement target, UNEP said countries should focus on keeping the rise as low and short-lived as possible while cutting greenhouse gas emissions.
“The challenge has shifted from avoiding overshoot to navigating it,” the report said.
The Paris Agreement, adopted by nearly 200 countries in 2015, called for efforts to limit global warming to 1.5C above pre-industrial levels. Scientists have warned that risks from extreme weather, rising seas and damage to ecosystems increase as temperatures rise.
The world has already warmed about 1.4C since 1850-1900, mainly because of fossil fuel emissions, while the last three years have been the hottest on record.
Richard Betts, a University of Exeter scientist who co-authored the report, said the findings were intended to help governments prepare for a warmer world while maintaining efforts to reduce emissions.
“It’s a reality check. We have to live with this warmer world, but there’s still a lot we can do to limit warming,” he said.
UNEP said the most favourable pathway would see temperatures peak at about 1.8C before declining. Returning below 1.5C would require deep and sustained cuts in greenhouse gas emissions, followed by net-negative emissions and carefully managed carbon removal.
The report has unsettled climate campaigners, who fear treating an overshoot as inevitable could weaken pressure for faster emissions cuts.
“This is a heartbreaking moment, but overshoot is not the reason to give up and surrender,” said Jasper Inventor, deputy program director at Greenpeace International.
Climate scientist Bill Hare, chief executive of Climate Analytics, said the report risked becoming “a call to apathy rather than a call to arms.”
UNEP Executive Director Inger Andersen said the 1.5C goal remained in place despite the changing outlook.
“There are no good outcomes if we remain above 1.5C,” she said.
U.N. Secretary-General Antonio Guterres has said temperatures could still be brought below 1.5C by the end of the century.
“The fight for 1.5 degrees is the fight for humanity,” he said
