The United States is the only nation that can lead the world toward a solution on climate change.

I have absolutely no plans and no expectations of ever being a candidate again.

Today we're dumping 70 million tons of global-warming pollution into the environment, and tomorrow we will dump more, and there is no effective worldwide response. Until we start sharply reducing global-warming pollution, I will feel that I have failed.

...the debate among the scientists if over. There is no more debate. We face a planetary emergency. There is no more scientific debate among serious people who've looked at the science...Well, I guess in some quarters, there's still a debate over whether the moon landing was staged in a movie lot in Arizona, or whether the Earth is flat instead of round.

Winston Churchill aroused this nation in heroic fashion to save civilisation in World War Two. We have everything we need except political will, but political will is a renewable resource.

Here is the truth: The Earth is round; Saddam Hussein did not attack us on 9/11; Elvis is dead; Obama was born in the United States; and the climate crisis is real.

I never like the question about letter grades, but I think Trump is failing. I think that every day there's another set of tweets and another set of controversies, and nothing seems to be getting done that's any good. And there seems to be kind of a policy paralysis in Washington. Even the appointments he's supposed to make as a new president, so I focus most of all on climate, and so my opinion of his time as president is certainly influenced by my opinion of the job he's done on climate. He's tried to move the country in the wrong direction.