We created a way of raising standards of living that we can't possibly pass on to our children.

We have been getting rich by depleting all our natural stocks - water, hydrocarbons, forests, rivers, fish and arable land - and not by generating renewable flows.

Protecting dozens of major coastal cities from future flooding will be challenging enough-rebuilding major coastal cities destroyed by super-hurricanes will be an almost impossible task.

The world beyond 450 ppm atmospheric concentrations of carbon dioxide, the world that crosses carbon cycle tipping points that quickly take us to 1000 ppm, is a world not merely of endless regional resource wars around the globe. It is a world with dozens of Darfurs. It is a world of a hundred Katrinas, of countless environmental refugees

The great political tragedy of our time is that conservative leaders in America have chosen to use their superior messaging and political skills to thwart serious action on global warming.

The entire western Siberian sub-Arctic region is melting, and it has all happened in the last three or four years.

On moral grounds, I think that if you believe a certain outcome is a very possible outcome, you have an obligation to tell people that. With global warming, the probability of a bad outcome if we stay on our current emission trends is incredibly high. If you know a bad outcome is likely to happen, what right do you have not to communicate that? You go into a doctor's office, what are they going to do - not tell you the diagnosis?