The main environmental challenge of the 21st century is poverty. When you don't know where your next meal is coming from, it's hard to consider the environment 100 years down the line.

I tentatively believe in a god. I was brought up in a fairly religious home. I think the world is compatible with reincarnation, karma, all that stuff.

Even if every major government were to slap huge taxes on carbon fuels - which is not going to happen - it wouldn't do much to halt climate change any time soon. What it would do is cost us hundreds of billions - if not trillions - of dollars, because alternative energy technologies are not yet ready to take up the slack.

The main environmental challenge of the 21st century is poverty. When you don't know where your next meal is coming from, it's hard to consider the environment 100 years down the line.

In the rich world, the environmental situation has improved dramatically. In the United States, the most important environmental indicator, particulate air pollution, has been cut by more than half since 1955, rivers and coastal waters have dramatically improved, and forests are increasing.