You're never going to get the amount of CO2 emitted to go down unless you deal with the one magic metric, which is CO2 per kilowatt-hour.

The nuclear approach I'm involved in is called a traveling-wave reactor, which uses waste uranium for fuel. There's a lot of things that have to go right for that dream to come true - many decades of building demo plants, proving the economics are right. But if it does, you could have cheaper energy with no CO2 emissions.

Almost every way we make electricity today, except for the emerging renewables and nuclear, puts out CO2. And so, what we're going to have to do at a global scale, is create a new system. And so, we need energy miracles.

The spread of online information isn't just good for charities. It's also good for donors. You can go to a site like Charity Navigator, which evaluates nonprofits on their financial health as well as the amount of information they share about their work.

My experience of malaria was just taking anti-malarials, which give you strange dreams, because I don't want to get malaria.

I don't have a magic formula for prioritizing the world's problems.