I saw the logarithmic growth of computer power.

It's an important point, and every little bit helps not least because those who make those kinds of changes are more likely to make their voices heard as citizens. But the ultimate solutions are going to come through policies.

It seems an easy choice - sacrifice the tree for a human life - until one learns that three trees must be destroyed for each patient treated. Suddenly we must confront some tough questions. How important are the medical needs of future generations?

You see that pale, blue dot? That's us. Everything that has ever happened in all of human history, has happened on that pixel. All the triumphs and all the tragedies, all the wars all the famines, all the major advances... it's our only home. And that is what is at stake, our ability to live on planet Earth, to have a future as a civilization. I believe this is a moral issue, it is your time to seize this issue, it is our time to rise again to secure our future.

There's lots about politics I don't feel comfortable with. To talk about the politics of future ideas is impossible in soundbite form.

There's no such thing as clean coal. It's non-existent. Theoretically, it might be possible, many years from now, to come up with a way to clean it as it's burnt. But there's not a single demonstration project in the United States. [...] Clean coal doesn't exist.

Our way of life is at stake, our grandchildren are at stake, the future of civilization is at stake.