Mr Trump said he was fulfilling his “solemn duty to protect America and its citizens”.
He added: “We don’t want other leaders and other countries laughing at us anymore – and they won’t be.”
What has the global reaction been?
Germany’s Angela Merkel delivered a fierce defence of the Paris accord on Friday.
She said: “We need the Paris agreement to protect all of creation. Nothing can and nothing will stop us.”
Mrs Merkel said the path set out by Paris was “irreversible”.
“We will travel it together. To everyone who cares about the future of our planet, I say let’s continue on this path together to succeed in protecting Mother Earth.”
European Commission President Jean-Claude Juncker, opening a summit on Friday with China in Brussels, said Mr Trump’s move was “seriously wrong”, adding: “There is no backsliding on the Paris agreement.”
UK Prime Minister Theresa May expressed her disappointment and told Mr Trump in a phone call that the deal protects the “prosperity and security of future generations”.
France’s President Emmanuel Macron reworked one of Mr Trump’s own phrases, saying: “Wherever we live, whoever we are, we all share the same responsibility: make our planet great again.”
Japan’s Finance Minister Taro Aso said: “I’m not just disappointed, but also feel anger.”
United Nations Secretary General Antonio Guterres said that the fight against climate change was “unstoppable”.
Small island nations whose existence is threatened by rising sea levels were also critical. The President of the Marshall Islands, Hilda Heine, said it was “highly concerning for those of us that live on the frontline of climate change”.
What happens next?
Mr Trump did not give a timescale on withdrawal. However, under the agreement, a nation seeking to leave the pact can only give notice three years after the date it entered into force – 16 November 2016.
The process of leaving then takes another year, meaning it would not be complete until just weeks after the US presidential election in 2020.
US payments to the UN Green Climate Fund, which helps developing countries cope with the effects of climate change, will stop. The US has reportedly so far paid $1bn (£780m) of a $3bn pledge.
Mr Trump indicated he was open to another climate deal, saying he would “begin negotiations to re-enter either the Paris accord or a really entirely new transaction on terms that are fair to the United States”.
However, his words suggested this was not a priority. “We will see if we can make a deal that’s fair. And if we can, that’s great. And if we can’t, that’s fine,” he said.
The leaders of France, Germany and Italy quickly issued a joint statement rejecting a renegotiation of the agreement.
“We deem the momentum generated in Paris in December 2015 irreversible and we firmly believe that the Paris agreement cannot be renegotiated, since it is a vital instrument for our planet, societies and economies,” they said.
What’s been said in the US?
Former US President Barack Obama, who agreed to the Paris deal, immediately criticised the move, accusing the Trump administration of “rejecting the future”.
Disney’s chief executive Robert Iger and the entrepreneur Elon Musk both resigned from White House advisory councils.
“Climate change is real. Leaving Paris is not good for America or the world,” said Mr Musk, the head of tech giant Tesla.
However, Republican congressional leaders and the US coal industry backed the move, with Senate Majority Leader Mitch McConnell supporting Mr Trump “for dealing yet another significant blow to the Obama administration’s assault on domestic energy production and jobs”.
Peabody Energy, America’s biggest coal mining firm, said the agreement would have badly affected the US economy.
The Democratic governors of New York, California and Washington states all quickly vowed to respect the terms of the Paris deal.
What was agreed in Paris?
Climate change, or global warming, refers to the damaging effect of gases, or emissions, released from industry, transportation, agriculture and other areas into the atmosphere.
The Paris accord is meant to limit the global rise in temperature attributed to emissions. Only Syria and Nicaragua did not sign up.
Countries agreed to:
- Keep global temperatures “well below” the level of 2C (3.6F) above pre-industrial times and “endeavour to limit” them even more, to 1.5C. However, US think tank Climate Interactive predicts that if all nations fully achieve their Paris pledges, the average global surface temperature rise by 2100 is expected to be 3.3C, or 3.6C without the US
- Limit the amount of greenhouse gases emitted by human activity to the same levels that trees, soil and oceans can absorb naturally, beginning at some point between 2050 and 2100
- Review each country’s contribution to cutting emissions every five years so they scale up to the challenge
- Enable rich countries to help poorer nations by providing “climate finance” to adapt to climate change and switch to renewable energy
Nasa’s Goddard Institute for Space Studies says the world’s average temperature has risen by about 0.8C since 1880, two-thirds of that since 1975.
By: BBC News