The fact that solar has gone down 80 percent since 2008 is astonishing. Wind is perhaps not coming down as quickly. Lack of storage - batteries - is a bottleneck. That makes it very difficult to put large amounts of renewable energy on the grid.

In a perfect world global emissions would have peaked already. In a semi-perfect world we will peak on Dec. 31, 2020. The fact is, that's going to be difficult. We know that it's going to get more and more expensive the longer we delay.

When you have a vision of where you need to go, it sounds utopian. But when you get to the tipping point, your understanding switches.

The fact that solar has gone down 80 percent since 2008 is astonishing. Wind is perhaps not coming down as quickly. Lack of storage - batteries - is a bottleneck. That makes it very difficult to put large amounts of renewable energy on the grid.

We will move to a low-carbon world because nature will force us, or because policy will guide us. If we wait until nature forces us, the cost will be astronomical.

This is probably the most difficult task we have ever given ourselves, which is to intentionally transform the economic development model, for the first time in human history.

We're going to get to the point where we ask how the hell we put up with high carbon for so many years. You thank your lucky stars, because you are seeing this transformation in your lifetime. You are going to tell your children and your grandchildren you saw this whole thing in front of your eyes.