Anyone who deals with the climate crisis has an internal dialogue between hope and despair, because the challenge is so huge and the danger is so great and the stakes are so high. But I have always resolved that in favour of hope, and actually I'm more hopeful now than I was a decade ago when the solutions were visible on the horizon, but you had to seek reassurance that the technology experts that they're coming, they'll be here.

We are seeing every night on the television news now a nature hike through the Book of Revelation. These climate-related extreme weather events have convinced the vast majority of people that the scientists have been right for a long time. We have to address this.

I have faith in the United States and our ability to make good decisions based on the facts.

The Congress is virtually incapable of passing any reforms unless they first get permission from the powerful special interests who are most affected by the proposal.

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.

In a free society, there comes a time when the truth - however hard it may be to hear, however impolitic it may seem to say - must be told.

Global warming is real and human activity is the main cause. The consequences are mainly negative and headed toward catastrophic, unless we act. However, the good news is that we can meet this challenge. It is not too late, and we have everything we need to get started.