Al Gore talks about global warming, those e-mails, and his new book.

We're already at the point where it's stretching our capacity to reach an agreement that will solve the problem, but it's still within our capacity. There are abundant reasons for hope that we will act in time. If you look at the difference between today and 10 years ago, there is a global consensus. More than 70 leaders from nations are gathering at Copenhagen. Many nations have taken action and the world is waiting for the natural leader, the United States to move on this.

Q: Must climate change go through the Senate? Is there another route through the EPA, the courts and the states?

A: Yes, but it's an imperfect alternative. Local and state governments have outrun the federal government. The EPA has served notice that it will enact a rule requiring CO₂ reductions by major emitters in the absence of major legislation. But it's a blunt instrument that is a little more difficult to use than a legislative remedy. But the existence of the EPA regulation will require large carbon polluters to look at their hole cards, and some of them have decided that they much prefer legislation.

Q: Do you think there will ever be a CO₂ tax?

A: I think eventually we'll use a CO₂ tax offset by a reduction in taxes elsewhere alongside a cap-and-trade plan, but the degree of difficulty associated with a CO₂ tax far exceeds that with a cap-and-trade plan. We're seeing it's hard to get a cap-and-trade plan and it's much easier to use as a basis for a global agreement than a CO₂ tax. 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.

Q: Vice Admiral Dennis McGinn has said that if you don't like wars in the Middle East and you're driving an SUV, you're not walking the walk. He said driving an SUV is a national security statement. What's your view?

A: I think it's true, but 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.

It's an important point, and every little bit helps not least because those who make those kinds of changes are more likely to make their voices heard as citizens. But the ultimate solutions are going to come through policies. We need to put a price on carbon, and that's what cap-and-trade does and that's also what a CO₂ tax does. As long as our current valuation in the marketplace tells us every minute of every day that it's perfectly all right to dump 90 million tons of global warming into the thin atmosphere surrounding the planet every 24 hours as if that atmosphere is an open sewer, then the individual actions are not going to solve the problem.

Q: Your critics say that you have a lot of investments in green technology and say, "Isn't he sounding the alarm here to make himself rich?"

A: That's not my principal business. I've been fortunate over the last eight years to be successful in business. But most of my success has been in Internet and media companies, and yet my wife and I have made some investments in renewable energy ideas that I think are good ideas. If I didn't [invest], I'd be accused by the same people of being a hypocrite and not being willing to put my money where my mouth was.