Well into An Inconvenient Truth, a new film that features the former next president of the United States explaining the accelerating and devastating impact of too much carbon dioxide in the earth's atmosphere, there is a moment of unexpected emotional force. Standing in the skeletal remains of a barn on his family's estate in Tennessee, Al Gore, 58, relates how the barn was once used to cure the tobacco his family sold in addition to its cattle business. The barn remained in use up until his sister, a smoker, died of lung cancer, after which Gore's heartbroken dad tore out the tobacco and decommissioned the barn. The relevance of this story to climate change isn't immediately clear, but it becomes so as Gore laments that his family didn't heed the reports that linked smoking to cancer. It took the loss of a loved one, he says, for the news to sink in. Similarly, Gore says, "the scientific community is now giving us such clear and unambiguous warnings about the consequences of global warming, we should not ignore them." MJ spoke to the citizen-crusader just ahead of the May 26 release of An Inconvenient Truth.

When and why did you become so passionate about global warming?

As an undergraduate I had a professor named Roger Revelle who was the first person to propose measuring CO2 in the earth's atmosphere, and he showed the first several years of measurements to the small class he taught. It was a startling picture. It was already clear after the first eight or nine years of data [what was happening]. He was a charismatic and compelling scientist, and I continued to keep in touch with him and to follow the data. Later, after I was elected to Congress in 1976, I helped organize the first hearings on global warming in Congress, and I asked my professor to be the leadoff witness. I hoped that he would have the same effect on Congress that he had on me and my college class, but it didn't turn out that way.

Why didn't it? Why is Congress still dragging its feet on global warming?

Well, it's a big problem, and it's a complex problem, and there are vested interests that don't want to see any change. Some of them, in the oil and coal industries, have worked very hard to paralyze the political system.

The Bush administration has said that signing the Kyoto Protocol -- the 1997 international pledge to reduce greenhouse gas emissions -- would severely hurt the U.S. economy. Is that true?

No, I think the opposite is true. If you look at the American automobile industry -- the industry has successfully lobbied the United States government to have the lowest emissions standards in the world. And yet if you look at the automobile marketplace, the companies that are doing well are the ones that have the best emissions standards.

Sci-fi author Michael Crichton recently testified before Congress on this topic. In his latest novel, State of Fear, he implies that scientists and enviros are getting rich off global warming alarmism.

I think Michael Crichton is getting rich off of the distortion of global warming, but I don't think scientists are lying in order to earn their salaries. I think the ones who are getting money from ExxonMobil and other special interests may be more vulnerable to that accusation.

What about those who say, okay, there's global warming, but all of the greenhouse gases humans have contributed to our atmosphere are negligible compared to, say, the release from Mount St. Helens when it erupted in 1980.

Large volcanic eruptions typically reduce the amount of sunlight hitting the earth's surface for about a year and a half, but then the particulates [from the eruption] fall to the ground and the impact of the eruption is sort of over. But where carbon dioxide emitted by the burning of fossil fuels is concerned, these gases stay in the atmosphere for a hundred years or more. And that's what traps the heat from the sun.

Instead of coal and oil, do you favor windmills and clean nukes?

There's no doubt that windmills are going to play an enormous and important role. The question as regards nuclear reactors is a bit more complicated. It's not just the waste storage and terrorism issues that I'm talking about. There has been an underappreciated linkage between civilian nuclear power programs and the proliferation of nuclear weapons.

So no new nukes?

No, I'm not an absolutist. It's just that I'm skeptical.

Have you and Tipper made the switch to a hybrid?

Yeah, we just got a Lexus hybrid, and our family are big fans of the Prius.

What's your honest take: Will we see, in your lifetime, large-scale catastrophe related to global warming?