Every fraction of a degree above 1.5 degrees Celsius will increase climate risks, the United Nations warned on Wednesday, saying countries must move quickly to limit how far temperatures rise and how long they remain elevated.
A new report by the U.N. Environment Programme says the world is likely to cross the 1.5C threshold within the next few years. Even under the most ambitious pathway, warming could peak at about 1.8C before temperatures begin to fall.
The report marks a shift in climate planning, with governments urged to prepare for an “overshoot” period while continuing efforts to cut emissions and eventually return global temperatures below 1.5C.
Higher temperatures would intensify extreme weather, ecosystem losses and threats to food, water supplies, health and infrastructure. The report also warns that longer periods of elevated warming increase the risk of crossing irreversible climate tipping points.
UNEP Executive Director Inger Andersen said the prospect of exceeding 1.5C should not weaken efforts to curb emissions.
“There are no good outcomes if we remain above 1.5C,” she said.
The Paris Agreement, reached by nearly 200 countries in 2015, called for efforts to keep the increase in global temperatures to 1.5C above pre-industrial levels.
The world has already warmed about 1.4C since 1850-1900, largely because of burning fossil fuels. The past three years have been the hottest on record.
Returning below 1.5C after an overshoot would require steep and sustained cuts in greenhouse gas emissions, followed eventually by net-negative emissions. Carbon dioxide removal, including through afforestation and other methods, would play a role, UNEP said.
Richard Betts, a University of Exeter scientist who co-authored the report said the aim was to help governments respond to a warmer climate rather than accept it as inevitable.
“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.
The report has drawn concern from climate campaigners who fear that accepting an overshoot could reduce pressure on governments to act.
“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.
Bill Hare, chief executive of Climate Analytics, said the report risked becoming “a call to apathy rather than a call to arms.”
U.N. Secretary-General Antonio Guterres has said temperatures could still be brought below 1.5C by the end of the century.
