There's certainly no technical or economic barrier in the way. Scientists like James Hansen tell us we may need to eliminate net CO2 emissions from the economy in just a few decades. I wanted to know what that would take, so I worked with professor Jorgen Randers from Norway to find the answer. We developed a plan called "The One Degree War Plan" — so named because of the level of mobilization and focus required. To my surprise, eliminating net CO2 emissions from the economy in just 20 years is actually pretty easy and pretty cheap, not very cheap, but certainly less than the cost of a collapsing civilization. We didn't calculate that precisely, but we understand that's very expensive. You can read the details, but in summary, we can transform our economy. We can do it with proven technology. We can do it at an affordable cost. We can do it with existing political structures. The only thing we need to change is how we think and how we feel. And this is where you come in.