After a three-year delay, the US has become the first nation in the world to formally withdraw from the Paris climate agreement.
President Trump announced the move in June 2017, but UN regulations meant that his decision only takes effect today, the day after the US election.
The US could re-join it in future, should a president choose to do so.
The Paris deal was drafted in 2015 to strengthen the global response to the threat of climate change.
It aims to keep the global temperature rise this century well below 2C above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5C.
Source: BBC