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 climate change is presenting the greatest challenge humanity has ever faced.

The cumulative amount of man-made global pollution that's in the atmosphere now traps as much extra heat energy every day as would be released by 400,000 Hiroshima-class atomic bombs exploding every day. It's a big planet, but that's an awful lot of energy.

Although I have a variety of obligations, the climate crisis is my central concern.

We have a planetary emergency. We have to find a way to create, in the generation of those alive today, a sense of generational mission.

If youre a young person looking at the future of this planet and looking at what is being done right now, and not done, I believe we have reached the stage where it is time for civil disobedience to prevent the construction of new coal plants that do not have carbon capture and sequestration.

Someone who expresses a view that is contrary to the view of the overwhelming majority should be allowed to stand undisturbed as a monument to our commitment to free speech.