You can say the Earth is flat, but it doesn't mean you're going to fall off the edge.

As long as the government's actions are secret, it cannot be held accountable. A government for the people and by the people should be transparent to the people.

There's such a wide variation in tax systems around the world, it's difficult to imagine a harmonized CO2 tax that every country agrees to. That's not in the cards in the near term. But the countries that are doing the best job, like Sweden, are already doing both of these. I think that eventually we'll use both of them but we need to get started right away and the cap-and-trade is a proven and effective tool.

The planet has a fever. If your baby has a fever, you go to the doctor. If the doctor says you need to intervene here, you don't say, `Well, I read a science fiction novel that told me it's not a problem.'... You take action.

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.

Today I challenge our nation to commit to producing 100 percent of our electricity from renewable energy and truly clean carbon-free sources within 10 years.

I've learned the importance of changing people's minds at the grassroots level so that whoever does run will have a much better chance of encountering public opinion that reaches a critical mass and brings about a change not only in White House policies but in the Congress and in the state legislatures and all around the world.