The United States on Wednesday formally left the Paris Agreement, a global pact forged five years ago to avert the threat of catastrophic climate change.
The move, long threatened by US President Donald Trump and triggered by his administration a year ago, further isolates the United States in the world but has no immediate impact on international efforts to curb global warming.
Some 189 countries remain committed to the 2015 Paris Agreement.
Moving forward the agreement aims to keep the global increase in average temperatures worldwide “well below” two degrees Celsius, ideally no more than 1.5 Celsius, compared to pre-industrial levels.
A further six countries have signed, but not ratified the pact.
Scientists said any rise beyond two degrees Celsius could have a devastating impact on large parts of the world, raising sea levels, stoking tropical storms and worsening droughts and floods.
The Paris Accord requires countries to set their own voluntary targets for reducing greenhouse gases such as carbon dioxide.
“Donald Trump seems to think the United States should go it alone and to an extent he has a point when he talks about the US not getting its military entangled all over the world,” said Larry Donnelly, a US law expert at University College Galway and Democrat Abroad spokesperson.
“But I think diplomatic engagement on issues like this – and especially an issue like climate change which affects us all.
To rejoin the Paris Agreement, a president would have to issue a formal notification to the U.N., and would be able to rejoin 30 days later.