It is critical that the world captures every last bit of energy efficiency, if we are to reduce greenhouse gas emissions enough to keep below dangerous rises in temperature. I am pleased that this important new study shows how information and communication technology can play an essential role in saving energy. Now we need more and effective government policies that reward such action and penalize delayed responses.

We are just about to cross the 400 parts per million threshold.

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 shouldn't have stupid cars that use liquid fossil fuels. Come on, how outmoded is that? We have to get to the point where this is no longer a part of our experience.

The fact is, when you talk to people, they know that something weird is going on, particularly people who are connected to the land or the water. They can see it. What perhaps is not so evident to them, unfortunately, is what the solution is. But whether they call it climate change or not, it doesn't matter. The point is, they can see there's something fundamentally weird going on here.

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.