I don't have the illusion that there's any position or role in the world with as much potential for bringing about change as that of president of the United States.

The crisis is a concrete threatening reality today. It stands to get catastrophically worse unless we take action before the accumulation [of] this global warming pollution reaches such toxic levels that the problem becomes bigger than we can solve.

We're all capable of mistakes, but I do not care to enlighten you on the mistakes we may or may not have made.

There are skeptics who do not come to their view because they have a source of income from carbon polluters. I don't mean to imply that they're all in that category at all. There are also those who are also not motivated by ideological resistance for any role of government. But I don't know of any arguments or any presenters of arguments that overturn the consensus that I think have gained any legitimacy.

Fifteen per cent of the population believe the moon landing was actually staged in a movie lot in Arizona and somewhat fewer still believe the Earth is flat. I think they all get together with the global warming deniers on a Saturday night and party

Of all the works of civilization that interfere with the natural water distribution system, irrigation has been by far the most pervasive and powerful.

The scientists are virtually screaming from the rooftops now. The debate is over! There's no longer any debate in the scientific community about this. But the political systems around the world have held this at arm's length because it's an inconvenient truth, because they don't want to accept that it's a moral imperative.