We should educate more women and girls. Because that is the surest route to controllably, manageably reducing the human population. Educated women have fewer kids. And the kids they do have are better cared for and are more successful. As I like to say, it's not one thing that we need to focus on. It's everything all at once.

Talk about science with everyone you meet. Especially talk about climate change. It needs to become a part of our everyday conversation (the way it is everywhere else in the world).

Millennial voters are very concerned about climate change and will vote for candidates who are planning to address it. But the systems that are in place - people talk about gerrymandering and the money that's in politics, this is a real thing, a real effect - and it's hard for climate change-denying legislators to get voted out. But I predict it will happen.

Not wasting any water bottles is good. Not leaving the lights on is good. Turning the thermostat down in the winter, up in the summer, is good. But the best thing any of us in the developed world, especially in the United States, can be doing is talking about it.

It is my mission to change the world. I'm not kidding: Make no small plans, dream mighty things. I feel if we get enough people engaged in climate change, we will get enough people to change the world. We will revolutionize the way we produce electricity and provide clean water to people.

To leave the world better than you found it, sometimes you have to pick up other people's trash.

I try to speak plainly and be sympathetic to the idea of religions where people gather in community. They get a sense of people looking out for each other. My claim is that we have a tendency to look out for each other whether or not there is a religion involved.