United Nations: The US has formally served notice that it is withdrawing from the Paris Agreement that was drawn to fight climate change.
Secretary of State Mike Pompeo announced on Monday that the US sent the notification to the UN starting the year-long process of ending Washington's participation in the climate deal.
The US, which put out 5 billion tonne of carbon dioxide (CO2) last year, ranks behind China as the second biggest producer of the gas that is responsible for global warming.
World's biggest polluters
But on a per capita basis, Americans are the world's biggest polluters, putting out 15.3 tonnes of the gas each.
The pullout from the agreement fulfils President Donald Trump's election pledge to his base which is wary of international agreements.
Pompeo said: "President Trump made the decision to withdraw from the Paris Agreement because of the unfair economic burden imposed on American workers, businesses, and taxpayers by US pledges made under the Agreement."
Monday was the third anniversary of the Paris Agreement coming into force after it had been ratified by the required number of countries.
Significantly, the withdrawal will come into force the day after the US presidential election on November 4, 2020, a year after the formal notice is served.
Former Vice President Al Gore, who was awarded the Nobel Peace Price for his climate activism, said the decision to return to the agreement "is ultimately in the hands of the voters" because they can elect a president, who supports it next year.
"It would take just 30 days for a new president to get us back in," he said.
Unlike Trump, all the Democratic Party candidates for the presidential nomination are strong supporters of the Paris Agreement, which committed the US to cut its carbon emissions from the 2005 level by 26 per cent by 2025.
Joe Biden, who was the vice president when the US signed the Paris Agreement and is now a candidate to run against Trump next year, called scrapping the deal, "shameful".
He tweeted, "As the climate crisis worsens each day and California burns and Iowa floods, Trump continues to abandon science and our international leadership."
Stephane Dujarric, the spokesperson for UN Secretary-General Antonio Guterres acknowledged the receipt of the notification but made no comment about it. When Trump announced his decision in 2017, Guterres had called it a "major disappointment for global efforts" against climate change.
The Paris Agreement reached in 2015 aims to keep global temperature rise to 2 degrees Celsius above the pre-industrial levels and to work towards achieving a 1.5-degree limit.
Trump announced his plans to quit the Paris deal in 2017, complaining that they imposed "draconian financial and economic burdens" on Americans.
Trump has cut back on efforts introduced by President Barack Obama's administration to combat climate change, scaling back the regulations to tighten auto emission standards and discourage the use of coal for power generation.
However, as Pompeo pointed out, "The US has reduced all types of emissions, even as we grow our economy and ensure our citizens' access to affordable energy."
"US net greenhouse gas emissions dropped 13 per cent from 2005 to 2017, even as our economy grew over 19 per cent," he said.
The lead in combating climate change has now been taken by state and local governments and by industry, which sees financial gains from a green economy.
"In the two years since Trump first announced his intention to withdraw, we have seen unprecedented commitments from civic leaders, mayors, governors, investors, and the business community to ensure that the US remains a global leader in confronting the climate crisis," Gore said.
The US auto industry, for example, is continuing to accept the stricter auto emission standards that California has set, even though Trump has sought to prevent the state from enforcing them.
The US government's Energy Information Agency forecast that US CO2 emissions will go down by 2.2 per cent this year, nearly all of it due to fewer emissions from coal consumption.
When Trump announced his plan to quit the agreement, Dujarric said that Guterres was confident that cities, states and businesses within the US will continue to lead the way to low-carbon economic growth that will create quality jobs and markets.
Pompeo gave an assurance that despite leaving the agreement, "Just as we have in the past, the US will continue to research, innovate, and grow our economy while reducing emissions and extending a helping hand to our friends and partners around the globe."