The greatest danger hanging over our children and grandchildren is initiation of changes that will be irreversible on any time scale that humans can imagine.

Coal is the single greatest threat to civilization and all life on our planet.

How long have we got? We have to stabilize emissions of carbon dioxide within a decade, or temperatures will warm by more than one degree... We don't have much time left.

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

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.

It's as certain that as long as fossil fuels are the cheapest energy, we will just keep burning them.

The trains carrying coal to power plants are death trains. Coal-fired power plants are factories of death.