Barack Obama has said almost 200 countries "came together around the strong agreement the world needed" in agreeing a deal on climate change.
The US President said no agreement was perfect, including the Paris accord.
But he added that it was the best chance to save the planet.
Labour leader Jeremy Corbyn has welcomed the historic climate change deal agreed in Paris - and said he hopes it will prompt the government to reverse cuts to clean energy.
Accusing Prime Minister David Cameron of "taking us backwards on climate change action", Mr Corbyn said the challenge now was to turn the words of the agreement into action.
The Paris climate change agreement is historic in its ambition to take action against the worldwide threat of global warming. It represents a victory for the international movement for climate change action and global justice.
The challenge now is to turn the Paris agreement’s fine words into the strong action the planet and its people need.
The Labour Party will do everything we can to ensure Britain takes a leading role in making these aspirations a reality.
The Prime Minister has so far failed to show the leadership this agreement demands. In fact, the government has been taking us backwards on climate change action, including by cutting support for feed-in tariffs and the solar industry.
David Cameron must now take his cue from Paris, reverse his government’s cuts to clean energy and put real investment in the green jobs of the future.
The Friends of the Earth chief executive has warned the deal fell far short of the "soaring rhetoric" from 150 world leaders who attended the opening day of the talks.
An ambition to keep global temperature rises below 1.5C is all very well, but we still don't have an adequate global plan to make this a reality. This agreement leaves millions of people across the world under threat from climate-related floods, droughts and super-storms.
However, this is still a historic moment. This summit clearly shows that fossil fuels have had their day - and that George Osborne's outdated, backward energy policies must be reversed if he wants to be on the right side of history.
There are tears and smiles as the climate change deal was agreed in Paris, ITV News Science Correspondent Alok Jha reports.
The International Monetary Fund chief has hailed the landmark agreement reached in Paris "a critical step forward" for addressing global climate change in the 21st century and said her key message is to "price carbon right."
Governments must now put words into actions, in particular by implementing policies that make effective progress on the mitigation pledges they have made.
Charging for the emissions of fossil fuels puts in place the needed incentives for low-carbon investments; it also provides revenues to safeguard the poor, reduce debt, and lower the burden of other taxes on households and businesses.
Prime Minister David Cameron has welcomed the final approval on an historic international deal to tackle climate change.Read the full story ›
Almost 200 countries have agreed to the terms of a new international deal to tackle climate change following United Nations talks in Paris.
The conference broke out into applause as French Foreign Minister Laurent Fabius banged down his gavel, signalling almost 200 countries had formally signed up to the agreement, aimed at slowing the pace of global warming.
WWF-UK's chief executive, David Nussbaum, writes for ITV News after the release of the final draft of the Paris Agreement on climate change.Read the full story ›
Labour's shadow energy and climate change secretary has welcomed the Paris climate deal, calling it an "historic moment to be celebrated".
Lisa Nandy said there was still "a huge amount of work" to ensure it is delivered upon.
For the first time ever the nations of the world have come together to agree that every single one of them will act to cut carbon pollution.
In the coming months and years we have a huge amount of work to do to deliver on the promises made in Paris, but this deal will take us much, much closer to climate safety. We now have a common goal of limiting temperature rises to 1.5 degrees and an international plan of action.
That matters, and it makes this a historic moment to be celebrated.
Campaigners at Greenpeace have welcomed a new UN deal on climate change, saying it was a good first step.
Charity chiefs also urged Prime Minister David Cameron to ensure action is taken to help meet the terms of the deal - and turn his back on the fossil fuel industry.
The glass is half full not half empty, but who is paying for the next round is the key question.
Will it be the fossil fuel industry that now has to be phased out or people across the globe who will ultimately pick up the tab if there is lack of action following the successful climate talks?
The recent floods in Cumbria have shown the answer has consequences for Britain. Now it's David Cameron's turn to decide whose side is he on - the old polluters who caused the problem or the new renewable technologies that have just been given a shot in the arm.