The symbolism - and the substantive significance - of planting a tree has universal power in every culture and every society on Earth, and it is a way for individual men, women and children to participate in creating solutions for the environmental crisis.

We have to abandon the conceit that isolated personal actions are going to solve this crisis. Our policies have to shift.

What changed in the United States with Hurricane Katrina was a feeling that we have entered a period of consequences.

Even though it's important for all of us to change our light bulbs and the vehicles we drive, it's much more important to change our laws and policies. I drive a hybrid and we've changed our light bulbs and windows and installed solar panels and geothermal ground source heat pumps and most everything else. But putting the burden on individuals to solve this global crisis is ultimately not going to be the most effective way to solve it.

Humanity is sitting on a time bomb. If the vast majority of the world's scientists are right, we have just ten years to avert a major catastrophe that could send our entire planet's climate system into a tail-spin of epic destruction involving extreme weather, floods, droughts, epidemics and killer heat waves beyond anything we have ever experienced - a catastrophe of our own making.

As many of you know, I was very instrumental in the founding of the Internet

The center of the earth is about a million degrees.