The United States did not sign Kyoto, yet its emissions are not that different from the countries that did sign it.

The climate system is being pushed hard enough that change will become obvious to the man in the street in the next decade.

The question is not whether to close the parks, but how to accomplish this goal.

A level of no more than 350 ppm is still feasible, with the help of reforestation and improved agricultural practices, but just barely - time is running out.

The last time the world was three degrees warmer than today-which is what we expect later this century-sea levels were 25m higher. So that is what we can look forward to if we don't act soon.

The carbon emissions from tar shale and tar sands would initiate a continual unfolding of climate disasters over the course of this century. We would be miserable stewards of creation. We would rob our own children and grandchildren.

We are on the precipice of climate system tipping points beyond which there is no redemption.