Flanked by coal miners during a visit to the Environmental Protection Agency, Donald Trump enacted what he calls his "Energy Independence" order.
"The action I'm taking today will eliminate federal overreach, restore economic freedom and allow our companies and our workers to thrive, compete and succeed on a level playing field for the first time in a long time, fellas, it's been a long time."
The order's main target is former President Barack Obama's Clean Power Plan, which required states to slash carbon emissions from power plants under a landmark deal signed in Paris in 2015 by nearly 200 countries.
President Trump's decree also reverses a ban on coal leasing on federal lands, undoes rules to curb methane emissions from oil and gas production, and reduces the weight of climate change in policy and infrastructure decisions.
The measures have alarmed environment experts across the globe, including Martin Hayden, the vice president of policy and legislation at non-profit law firm Earthjustice.
"It's a grab bag of terrible ideas by the fossil fuel industry top to bottom, designed to take us backward on progress on climate, not forward, at the very time when we and the world need to be moving forward."
In the past, Donald Trump has called global warming a "hoax" that was "created by the Chinese" to "make US manufacturing non-competitive".
The reversal is his boldest move yet to cut environmental regulation and revive America's drilling and mining industries.
But analysts, including Bob Deans from the National Resources Defense Council, have questioned whether it will in fact have the effect the President has been touting.
"The coal industry itself is telling us it's not going to create new jobs because due to automation in the coal industry, as everywhere else across the country, the coal industry is now getting more coal with fewer workers, we need to take care of those coal miners, we need to take care of those workers by doing things like transitioning them toward cleaner, smarter options."
Climate change specialist Ajay Gambhir, of Imperial College London, says the order also casts significant doubts on whether the US still supports clean technologies.
"The clean power plan represented a very, very big decrease in sulphur dioxide and nitrogen oxide emissions as well, and those are the chemicals that cause soot and smog. So there will be lots of potentially harmful impacts in terms of local pollution - the kind of stuff that causes asthma attacks, premature deaths and so on."
Australian experts are also watching the developments closely.
Dr Elena Aydos, an environmental law lecturer from the University of Newcastle, says the decree comes at "a very fragile moment" for Australian climate policy.
"We've seen over the last ten years a very toxic political debate around climate change. It was fuelled by misleading information and short-term interests of politicians. The interesting moment we have right now is that you see a number of stakeholders who traditionally would perhaps be against climate action, and suddenly they realise the lack of certainty we have in climate change policy is very concerning."
Dr Aydos remains cautiously confident that other countries will choose not to follow America's lead, particularly due to the falling costs of renewable energy and China's push towards cleaner technology.
"There are two ways we could see this unfold. One of them is the United States will lose more and more of its influence, perhaps even may see the consequences in terms of trade. The other possibility is at the subnational level the United States will still be pushing towards climate action, so we need to see whether or not the states will be strong enough to make a difference."
A coalition of 23 US states and local governments has vowed to fight the order in court.
