Is it 10 years, 20, 50 before we reach that tipping point where climate change becomes irreversible? Nobody can know. There's clearly a probability distribution. We need to ensure this planet, and we need to do it quickly.

Setting an aggressive enough carbon-reduction goal will result in an appropriate price for carbon and will help many a renewable technology. Consumer education will help. Most importantly, though, will be the continually declining cost trajectory of the real breakthrough in clean-technology costs driven by research and innovation. In the end, private capital is the real barometer of change.

There's no doubt in my mind over the next 25 years how we drive, how we build our houses, how we fly, how we build our buildings, will all change.

Religion asks you to believe things without questioning, and technology and science always encourage you to ask hard questions and why it is important in science and technology. So I was always interested in science and technology.

I've probably failed more often than anybody else in Silicon Valley. Those don't matter. I don't remember the failures. You remember the big successes.

Now it will take a long time to scale biofuels, but I'm the only one in the world forecasting oil dropping in price to $35 a barrel by 2030. I'll put it on the record: Oil will not be able to compete with cellulosic biofuels. If you do it from food, the food will get so expensive you can't make fuel out of it.

Communication always changes society, and society was always organized around communication channels. Two hundred years ago it was mostly rivers. It was sea-lanes and mountain passes. The Internet is another form of communication and commerce. And society organizes around the channels.