Well-established theories collapse under the weight of new facts and observations which cannot be explained, and then accumulate to the point where the once useful theory is clearly obsolete.

No controlling legal authority

The good news is, we have everything we need now to respond to the challenge of global warming. We have all the technologies we need, more are being developed.... But we should not wait, we cannot wait, we must not wait.

The truth is that we're at a critical juncture in the history of our species and if we don't act soon, we could inhabit a world we don't recognize anymore. But the most important truth is that we are capable of stopping climate change before the worst of its consequences are locked in. The solutions exist - all we need is the will to do something about it.

There is no doubt that the issue of race is always present in American politics and in the politics of any multiracial society. There is also no doubt that for some people it is an element in the manifested hostility to Obama. But I don't think it is the major theme at all. Obama is right when he reminds people: By the way, I was black before the election.

I don't really consider this a political issue, I consider it to be a moral issue.

We ought to approach this challenge [of global warming] with a sense of profound joy and gratitude: that we are the generation about which, a thousand years from now, philharmonic orchestras and poets and singers will celebrate by saying, they were the ones that found it within themselves to solve this crisis and lay the basis for a bright and optimistic human future.