Over the years US President Donald Trump has said many things about climate change and the role the United States should or should not play in efforts to deal with it.
RTÉ's Laura Fletcher takes a look back at what he has said.
Back in 2012, almost three years before he declared that he was going to run for the White House, Mr Trump tweeted: "The concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive."
The concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive.— Donald J. Trump (@realDonaldTrump) November 6, 2012
However, when Hilary Clinton spoke about this during their first presidential debate in New York on 26 September 2016, he denied it.
Here is how the exchange between the two presidential candidates unfolded:
Hilary Clinton: "... Donald thinks that climate change is a hoax perpetrated by the Chinese. I think it's real."
Donald Trump: "I did not. I did not. I do not say that."
Nevertheless pulling out of the Paris climate agreement, that was signed by President Obama in 2015, was a key campaign promise.
On 26 May 2016, Mr Trump told supporters in Bismark, North Dakota: "We are going to cancel the Paris Climate Agreement and stop all payments of the United States tax dollars to UN Global Warming Programmes."
As President-elect, in an interview with Fox News Sunday on 12 December 2016, he said that he was "still open minded" about whether climate change existed, adding that "nobody really knows". He said he was "studying" whether the United States should withdraw from the Paris Accord.
He made that decision on 1 June 2017.
Donald Trump: US to withdraw from Paris climate agreement but begin negotiations to 'make a deal that’s fair' pic.twitter.com/q4aNd7t84V— RTÉ News (@rtenews) June 1, 2017
In his speech delivered to the press in the White House Rose Garden, Mr Trump said: "In order to fulfil my solemn duty to the United States and its citizens, the US will withdraw from the Paris climate accord, but begin negotiations to re-enter either the Paris accords or a really entirely new transaction, on terms that are fair to the United States."
Shortly afterwards Italy, France and Germany issued a joint statement saying they "firmly believe that the Paris agreement cannot be renegotiated, since it is a vital instrument for our planet, societies and economies."
A recurring theme in Mr Trump's tweets about climate change over years has been that unusually cold weather seemed to disprove the concept of global warming.
In November 2011 he tweeted: "It snowed over 4 inches this past weekend in New York City. It is still October. So much for Global Warming."
It snowed over 4 inches this past weekend in New York City. It is still October. So much for Global Warming.— Donald J. Trump (@realDonaldTrump) November 1, 2011
In December 2013: "Ice storm rolls from Texas to Tennessee - I'm in Los Angeles and it's freezing. Global warming is a total, and very expensive, hoax!"
Ice storm rolls from Texas to Tennessee - I'm in Los Angeles and it's freezing. Global warming is a total, and very expensive, hoax!— Donald J. Trump (@realDonaldTrump) December 6, 2013
And last month he returned to the topic tweeting: "In the East, it could be the COLDEST New Year's Eve on record. Perhaps we could use a little bit of that good old Global Warming that our Country, but not other countries, was going to pay TRILLIONS OF DOLLARS to protect against. Bundle up!"
In the East, it could be the COLDEST New Year’s Eve on record. Perhaps we could use a little bit of that good old Global Warming that our Country, but not other countries, was going to pay TRILLIONS OF DOLLARS to protect against. Bundle up!— Donald J. Trump (@realDonaldTrump) December 29, 2017
Today, Mr Trump held a joint press conference with Norway's Prime Minister Erna Solberg, who reiterated her country's commitment to the Paris accord.
When he was asked about the deal, Mr Trump said that the Paris Agreement was unfair to the US, penalising it heavily for using its resources of coal, oil and gas and he said it hurt American businesses.
But he did suggest that he might consider returning to the deal, or a version of it.
At least he sort of did.
"Frankly, it's an agreement that I have no problem with, but I had a problem with the agreement that they signed, because, as usual, they made a bad deal. So we can conceivably go back in," he said.