He may have been denied the presidency, but he just might end up saving the planet.

Rush-hour Times Square is a mass of electronic billboards and idling cabs, the very essence of the fossil-fuel economy’s entrenched excess. High above the noise and traffic, in a small screening room, Al Gore is in an earnest blue suit, doing his best to convince a group of newspaper reporters, magazine commentators, and television anchors that the byproducts of our busy industrial lives pose the greatest threat ever faced by humanity. “I really do feel this is a planetary emergency,” he says fervently, just before rolling his new film, An Inconvenient Truth. The full-length documentary, directed by Davis Guggenheim—who has extensive film and TV credits—will be released this summer by Paramount Classics in thousands of theaters around the country. It will present the first serious look at the global climate crisis on the big screen. Says Gore, “We have to break through the Category 5 denial which is part of the U.S. political reality.”

Having been part and parcel of that political reality for 16 years in Congress and eight in the White House, Gore is the first to admit that he failed to energize the public during his time on the political stage. But thanks to Hollywood, the scientific community, and the climate itself, this journalist-turned-politician-turned-missionary believes he now has a second opportunity to win hearts and minds. A drumbeat of weather disasters, dramatized best in the catastrophic destruction wreaked by Hurricane Katrina, is bringing the reality home to Americans. Melting polar ice caps and drowning polar bears have become routine headlines. And the new movie will bring Gore’s slide show detailing the science behind global warming—which, by his own estimation, he has given more than a thousand times across the world in the past decade—to an audience that may reach in the millions. Gore is betting that this time the issue won’t slip off the public’s radar as it has in the past. “Unfortunately,” he told me, “Mother Nature is growing more insistent.”

Yet so are well-funded industry lobbyists and their allies, who increasingly acknowledge that global temperatures are rising but insist that the potential impact is wildly overstated. A National Review Online article on Gore’s film lambastes him as a “scaremonger,” arguing against what it calls “a half-baked environmental jihad that could waste possibly trillions of dollars.” These forces are working in lockstep with the White House, which shelved the Kyoto Treaty midwifed by Gore, deep-sixed recent legislation in the Senate designed to reduce greenhouse-gas emissions, and has put pressure on government scientists to keep their opinions about the impact of global warming to themselves. Meanwhile, the United States continues to pump nearly 6 billion tons of carbon emissions into the atmosphere every year, as much as Russia and China combined. When the 163 countries that signed the Kyoto Protocol meet in Nairobi in November to hash out the next steps in controlling global warming when the agreement expires in 2012, the world’s largest polluter will be on the sidelines.

After six years spent wandering in the post-political wilderness, Gore may now be in the right place at the right time. “This hasn’t been on the front burner,” said retired NBC anchor Tom Brokaw after the New York screening. “But now there is an inevitability about it, with Katrina and western droughts, and each passing scientific report.” The issue, however, lacks a high-profile advocate who resonates with the media. No Carl Sagan or Martin Luther King of climate science has emerged to capture the public’s imagination.

“This is a dramatic presentation of scientific evidence in a particularly effective way. And it could appeal to neutral, undecided, and casual observers.”

That leaves the field open to Gore, who recently wrote that “this crisis is not really about politics at all. It is a moral and spiritual challenge.” It is hard to question the man’s sincerity. Gore is a former divinity school student apt to bring his palms together Buddhist-style in thanks, and he has clearly done his science homework. But can a former vice-president and loser in a divisive presidential race do more than preach to the converted? “That’s open to question,” says Martin Kaplan, associate dean at the Annenberg School for Communication at the University of Southern California. But he adds that Gore’s movie differs from films like Fahrenheit 911, since it is driven more by data than by rhetoric. “This is a dramatic presentation of scientific evidence in a particularly effective way. And it could appeal to neutral, undecided, and casual observers.”

Gore’s slide show was seen in 2004 in Los Angeles by Laurie David—an environmental activist, TV producer, and wife of Curb Your Enthusiasm’s Larry David—and Lawrence Bender, producer of the blockbusters Good Will Hunting and Pulp Fiction. The idea for a film version was thus born. Playing himself, Gore is a modern-day Don Quixote, trundling his carry-on bags through a series of generic airports to reach the next stage with klieg lights where he can prop his computer and plead his case. We are reminded of his long-standing ties to the earth, forged during summers spent on the family farm in Tennessee. It’s not a political advertisement, but it is a sympathetic documentary with little room for skeptics, much less critics.

“I’ve felt before we were on the verge of a tipping point, only to see the political attention of the country distracted,” Gore says. “I don’t think that is possible this time.”

His slide-show presentation takes an Environmental Science 101 approach, using simple graphs and a snappy Matt Groening cartoon (showing those bad greenhouse gases beating up on friendly sunbeams) to explain the nature of the climate crisis. Charting the increase in carbon dioxide brought on by industrialization, Gore shows the results: melting glaciers, the shrinking Arctic ice cap, and the disappearing snows of Kilimanjaro. He then presents stark images of the earth overlaid with a projected sea-level rise—Florida is much smaller, and lower Manhattan’s Ground Zero is flooded. The impact on low-lying countries, from the Netherlands to Bangladesh, he notes, would be catastrophic.

Like any 101 course, Gore’s science, by necessity, simplifies an enormously complex system, which makes some scientists squirm. And the prospect of millions of Americans paying to learn about topics such as soil evaporation and oceanic carbonic acid as told by a politician seems hard to imagine. Yet Gore believes the movie will reach an audience primed to receive his transmission. “I’ve felt before that we were on the verge of a tipping point, only to see the political attention of the country distracted,” he says. “I don’t think that is possible this time.” Gore’s message, of course, is not just gloom and doom. He’s an experienced enough politician to know that Americans respond best to challenges rather than problems, even if the consequences for not meeting them must be dire and immediate. In the film he quickly outlines a half-dozen strategies for reducing emissions to below 1970s levels. These tactics, what he calls low-hanging fruit, include conservation as well as new technologies like nanotechnology—the manipulation of individual atoms to build devices that would require minuscule amounts of energy to function—that will make the United States more competitive, he says. Gore seems a bit defensive, however, when asked to elaborate on solutions. “I will be increasingly shifting the emphasis towards that side of it,” he says. “But there is no point in going into a lot of detail until the country is convinced we have to bite the bullet.”

Gore’s own conversion on the dangers of human-induced climate change came in a Harvard classroom back in the 1960s with Roger Revelle, an esteemed oceanographer and global warming pioneer who was tracking an increase in carbon dioxide and global temperatures. “I educated myself as thoroughly as I could, with an eye to translating this very large scientific problem into simple language,” Gore says. Shortly after the 28-year-old arrived in Congress in 1977—after stints as an Army reporter in Vietnam and an investigative journalist in Nashville—Gore invited Revelle to speak to his colleagues at a hearing before the House Science and Technology Committee. “I did actually and naively expect that this would be an epiphany for them as it was for me,” he recalls, laughing. It wasn’t. Still, Gore didn’t give up, and he went on to hold dozens of hearings on the subject in the House and then the Senate after 1986. Six years later he published Earth in the Balance, the first best-selling book on the threat, and was chosen to be Bill Clinton’s running mate.

Scientists and environmentalists welcomed Gore’s ascension to the White House. But he very quickly ran up against the limits of power—even during the brief honeymoon years of a Democratic House and Senate. An effort to impose a carbon tax proved a political debacle. When the Republicans took control of the House in 1994, Gore began to focus on the international scene instead. He saw the Montreal Protocol limiting chlorofluorocarbons to halt ozone depletion as the model for a worldwide agreement on reducing greenhouse-gas emissions. But unlike the Montreal agreement, Kyoto required a radical rethinking of nearly every industrial system. Shortly before the 1997 Kyoto meeting, the Senate resolved 95 to 0 that the United States would not sign a treaty that could harm the U.S. economy or let developing countries off the hook for the greenhouse gases they produce. Clinton and Gore, however, ignored the advice. “It was a fiasco,” says one former senior Clinton White House aide. The protocol signed by the United States and other countries called for industrialized nations to reduce global greenhouse-gas emissions to below 1990 levels by 2012. And it set aside the question of how accountable developing countries would be in controlling their emissions. Fearing a political rout, the White House never sent the Kyoto Protocol to the Senate for approval. The setback left Gore with little room to maneuver, and with only the questionable authority of a vice-presidential bully pulpit. “I went to every telegenic location I could find to promote the higher awareness of the crisis and what needs to be done,” he says. “I tried everything I knew to do.”

Nothing worked. Like President Wilson and his League of Nations, Gore helped birth an international vision—but one lacking its most important player, the United States. Yet he still sees Kyoto as a victory. “It is now binding law in most of the world, and multinationals that do business here as well as in the rest of the world have already begun to change,” he notes, citing General Electric’s new Ecoimagination program, which is designed to come up with new and cleaner technologies in lighting and appliances. But for nearly a decade in Washington, global warming has been at best ignored and at worst derided as a hoax perpetuated by doomsayers like Gore. “I told you earlier I felt I have failed in my mission so far,” he says. “But I’m not done yet.”

So is the 21st century Al Gore politician or prophet? “A messenger,” he says firmly. “A messenger of an inconvenient truth.” As for politics: “Been there and done that.” After running for national office four times, he says, “I think there are other ways to serve.” That may be simply the canned response of a career politician with an eye on his future. But Gore’s 30-year obsession with global warming has almost certainly been more political hindrance than help. And rather than campaigning during the past six years, he has been giving his free slide show not just to potential voters but to people around the world, from Beijing to Boston. “I gave it five times in Europe last week,” he says proudly.

The hard truth, according to Gore, is that the U.S. political system can only put forward “pitifully inadequate” solutions. “The first task must be to change the minds of the American people—not only about the reality of global warming but about the urgency with which we must begin to confront it,” Gore insists. Like the climate, he adds, the political system can appear moribund only to change rapidly. “I’ve seen it time and time again,” he says. “We saw it in the civil rights movement when it was redefined as a moral issue, and I think we’re about to see it on the climate crisis as it is redefined as a moral issue.”

Whether he can convince the public that acting on global warming is comparable to desegregating buses and schools remains to be seen. But Gore today is more outspoken, more passionate, and less wooden than he was on the campaign trail. He decries the “cynical disinformation campaign” by industry to undermine the science of global warming, and, like a good investigative reporter, he connects the dots among lobbyists, White House officials, and companies involved in the effort to discredit the research. He has made himself “carbon-neutral” by donating money to build solar cookers in India to offset his frequent auto and plane travels (the making, promotion, and distribution of the movie itself, he adds, are carbon-neutral). And he is organizing a training program so that a thousand people can fan out across the world to give his slide show.

Global warming may need Al Gore, and Al Gore may need global warming. “Imagine for just a moment that everything I’m saying about this is true—then nothing else matters very much,” he says, leaning close. “And if [NASA climate scientist] Jim Hansen is correct that we have less than 10 years before we cross the point of no return, then why would you spend your time on anything else?” If Hansen is right and Gore proves effective, the world may look back on the outcome of the 2000 election with gratitude.