Philip Mahamat, a former French president, said the Paris accord did not deal not only with climate change, but also with other dangers of climate change.

“I think that in the last six months, we have come to the conclusion that we have lost the ability to take action on climate change,” he told France Info radio.

“Now climate change is our enemy,” he said. “We will have to take urgent measures to tackle this.”

A report on Tuesday by the International Monetary Fund (IMF) said the global economy will be hit by up to 4.3 percentage points of recession in 2020 if climate change and fossil fuels were left unchecked. The report does not identify any possible policy steps.

Trump’s move could mean more severe and far-reaching disruptions to the global economy as well as to the American and world military and intelligence agendas, as the United States moves toward reestablishing an influential role in the world order and in the global climate change system.

“It’s the end of the United States as the global leader of climate change action”

That is a major blow to the United States’ diplomatic success in the last century, said Chris Stringer, a former U.S. diplomat who was a member of Donald Trump’s Republican staff when he was president-elect. But Trump’s rhetoric was different than Obama’s, and U.S. companies and policy makers had a different vision of what the president-elect would do, he said.

“It will be very, very difficult,” Stringer said. “But they’re starting up again…. It’s quite extraordinary.”

He said U.S. diplomats were trying to help Europe and Japan, which are both big carbon emitters, develop their own plans to cut carbon to mitigate rising temperatures. “We’re working on it as well,” he said.

The Paris accord had a strong incentive to come together because it was agreed at the 2012 Conference of the Parties (COP21) in Paris to limit warming to about 2 degrees Celsius (3.6 degrees Fahrenheit) since pre-industrial times before 2100, when the world’s species — particularly humans — are expected die off. The agreement is the world’s most expensive climate deal ever — more than $739 billion — but it was widely seen as a milestone in combating climate change.

On Thursday, the head of the U.N.’s Environment Program