US President Barack Obama has said The climate deal reached in Paris is "the best chance we have to save the one planet we have".
He said it could be a "turning point" for the world to take on the challenge of a low-carbon future.
China, the world's biggest polluter, also hailed the deal. But some campaigners said it did not go far enough to protect the planet.
Nearly 200 countries took part in tense negotiations in the French capital over two weeks, striking the first deal to commit all nations to cut emissions.