President Donald Trump has once again vowed to withdraw the US from the Paris Climate Agreement, the world's most important effort to tackle rising temperatures.

The first Trump administration made a similar move in 2017, but that step was promptly reversed on President Joe Biden's first day in office in 2021.

The US will now have to wait a year before it will be officially out of the pact. The White House announced a "national energy emergency", outlining a raft of changes that will reverse US climate regulations and boost oil and gas production.

It comes after global temperatures in 2024 rose more than 1.5C above pre-industrial levels for the first time in a calendar year.

While the Paris Agreement is not a legally binding treaty, it is the document that drives global cooperation to limit the causes of global warming.

President Trump's antipathy to this cooperative approach was echoed in his statement in 2017 that he had been elected to "represent the people of Pittsburgh and not Paris".

This temperature threshold was established in the Paris Agreement as a level beyond which the world would face extremely dangerous impacts.

The US will now join Iran, Yemen and Libya as the only countries to currently stand outside the agreement, which was signed 10 years ago in the French capital.

At the White House on Monday evening, Trump signed the order to withdraw from the Paris climate accord, including a letter to the United Nations explaining the decision.

He also announced a "national energy emergency" to reverse many of the Biden-era environmental regulations.

Trump called the Paris agreement a "ripoff" during a speech at the Capital One Arena in Washington, DC, following his swearing-in.

"We will drill, baby, drill," he said earlier in his inaugural address.

The new president also vowed the US would embark on a new age of oil and gas exploration.

"We will bring prices down, fill our strategic reserves up again, right to the top, and export American energy all over the world," he told the audience.

"We will be a rich nation again, and it is that liquid gold under our feet that will help to do it."

However, US fossil fuels are already flowing like never before.

Since 2016, production of American oil has gone up by 70%, and the US is now the world's dominant producer and exporter.

Similarly, Liquified Natural Gas (LNG) exports have gone from almost zero in 2016 to the US becoming the global lead.

The new administration says the president will also end the "green New Deal", a reference to the Inflation Reduction Act, Biden's signature climate policy that channelled billions into clean energy.

The president says he will also cancel efforts to boost ownership of electric vehicles, what he terms the Biden "EV mandate", and he will strengthen efforts to save the US car industry.

He will also end the leasing of federal lands and waters to "massive wind farms that degrade our national landscape".

UN climate chief Simon Stiell said that America risks missing out on a global clean energy boom that was worth $2tn last year.

"Embracing it will mean massive profits, millions of manufacturing jobs and clean air," he said in a statement.

"Ignoring it only sends all that vast wealth to competitor economies, while climate disasters like droughts, wildfires and superstorms keep getting worse, destroying property and businesses, hitting nationwide food production, and driving economy-wide price inflation."

President Trump's previous effort to pull the US out of the Paris agreement served as a rallying cry for many Americans who were dismayed by leaving.

Internationally the US withdrawal was also a unifying force for countries.

This time round though the pull-out may be far more damaging to the global effort to limit emissions, as climate change has dropped down the list of priorities for governments.

There are other countries such as Argentina, who might follow in the US footsteps.

Developing nations are also fuming after COP29 in Azerbaijan when the richer world struggled to improve funding support.

But having survived the previous Trump attack, there is also a sense that this may not be the last US word on the Paris pact.

"The door remains open to the Paris agreement, and we welcome constructive engagement from any and all countries," said the UN's Simon Stiell.