The accord, which took years of worldwide negotiations to reach, differed from previous environmental treaties in that it called upon all countries - rich and poor, developed and developing - to commit to voluntarily lowering their emissions of planet-warming greenhouse gases.
The notification begins a one-year process of exiting the global climate change accord, culminating the day after the 2020 USA election.
Countries were not legally required to meet particular targets and they were given the flexibility to set their own goals. Secretary of State Mike Pompeo sent the United Nations a formal letter on Monday afternoon.
"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", Pompeo wrote in a statement announcing the decision. "The United States has reduced all types of emissions, even as we grow our economy and ensure our citizens' access to affordable energy". Instead, he said, private sector innovation had helped grow the USA economy while reducing emissions - pointing to a reduction in greenhouse gas emissions between 2005 and 2017 of 13%.
Former vice president turned climate champion Al Gore deplored Trump's decision - but said that a new president could re-enter the Paris accord within 30 days. "They rely for so much, and we would be giving them so little".
He said that the United States will "continue to offer a realistic and pragmatic model" in global negotiations.
Formally getting out of the Paris agreement is bad, but at this point after years of rhetoric is more symbolic than anything, said Georgia Tech climate scientist Kim Cobb.
But emissions of carbon dioxide, the leading greenhouse gas, rose in 2018, according to the U.S. Energy Information Administration, and while those emissions are expected to decline in 2019 and 2020, the EIA reports that is mostly because of "milder weather ... and, consequently, less energy consumption" and emissions still won't fall beneath 2017 levels.
Others, however, see America backing out of the worldwide pact to limit greenhouse gas emissions as an abdication of global leadership and denial of basic climate science.
"Donald Trump is the worst president in history for our climate and our clean air and water", said Michael Brune, the executive director of the Sierra Club.
Climate change advocates and experts have consistently criticized Trump for stepping back from climate change as a priority.
In his statement Monday, however, Pompeo maintained that the United States was on the right track both economically and environmentally.
Trump's decision will turn the USA into an outlier. It won't happen without US leadership.