US president Donald Trump has announced that the USA, which creates 15% of the world’s emissions of carbon dioxide, is to withdraw from the 2015 Paris climate agreement, and that moves to negotiate a new "fair deal” on emissions reduction that would not disadvantage US businesses and workers will now get under way. Mr Trump said during last year's presidential election campaign that he would take this step, to help his country's oil and coal industries.
The Paris agreement commits 195 countries, including the USA, to keeping the global temperatures rise "well below" 2°C and endeavouring to limit it more, to 1.5°C. Only Syria and Nicaragua did not sign up to the deal.
Mr Trump claimed the Paris agreement would cost the USA $3tn in lost GDP and 6.5 million jobs – while rival economies like China and India were treated more favourably. "In order to fulfil my solemn duty to protect America and its citizens, the United States will withdraw from the Paris climate accord … but begin negotiations to re-enter either the Paris accord or a really entirely new transaction on terms that are fair to the United States," he said.
Mr Trump did not give a timescale for US withdrawal, but White House sources had earlier suggested it could take up to four years. This is the time it would take if the USA were to follow the laid down procedure for withdrawal. 
US withdrawal will undeniably make it more difficult for the world to reach the goals that it set for itself in the Paris agreement. Although the USA contributes about 15% of global emissions of carbon, it is also a significant source of finance and technology for developing countries in their efforts to fight rising temperatures.
The move has been supported by the US coal industry and by the states of Nicaragua and Syria, which are not signed up to the Paris accord, but otherwise reaction around the world has been swift and angry. 
Opponents, including John Kerry, who was the US’ chief representative in the Paris negotiations, called it a ‘gross abdication of leadership’. Former US president Barack Obama immediately criticised the move, accusing the Trump administration of "rejecting the future".
Senate Democratic leader Chuck Schumer called the decision "one of the worst policy moves made in the 21st Century because of the huge damage to our economy, our environment and our geopolitical standing".
Some of Mr Trump’s political allies came out in support. Republican congressional leaders 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".
But world leaders quickly condemned the move. The EU and China have re-affirmed their suppor of the Paris agreement. The leaders of France, Germany and Italy 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," it said.
In the UK Greenpeace commented: “The government that once launched the Apollo space programme and helped found the United Nations has today turned its back on science and international co-operation. By rejecting the Paris agreement Donald Trump has chosen to back the short-term profits of fossil fuel companies over the security, health, and prosperity of hundreds of millions of people in the US and the rest of the world.”
Trump will not mind the anger. To his supporters among the US electorate this shaking of his fist against the rest of the world will be the ideal image of the USA ‘being great again’ and ‘reasserting its sovereignty’, a position that Trump has carefully set up by his continual claims that the US is being pushed around by other nations. The Paris agreement is, in Trump’s mind, the epitome of that bullying. He characterises the Paris agreement as “a deal that aimed to hobble, disadvantage and impoverish the US.”  “I was elected to represent the citizens of Pittsburgh” he says “not the citizens of Paris”.