Friends who knew Al Gore in college still talk about their surprise that he ever went into politics. The son of a U.S. senator (Tennessee Sen. Albert Gore Sr.), he seemed to know too much about the personal costs of public life to find it appealing -- particularly the loss of privacy, the play-acting and the constant pandering to uninformed opinion.

Intellectually curious, irreverent and funny, Gore struck them as more likely to follow a career in which speaking one's mind brought rewards, not penalties. Somebody less like the losing party in Bush v. Gore, the most absurd Supreme Court decision in U.S. history, and more like the rueful protagonist of the documentary film "An Inconvenient Truth," who introduces himself to audiences around the world by saying, "I'm Al Gore, and I used to be the next president of the United States."

It always gets a laugh.

Which isn't to say that "An Inconvenient Truth" lacks a political edge. Nobody who followed the Washington press corps' "War on Gore" during the 2000 campaign could fail to notice that the film opens and closes with beautifully evocative shots of the Caney Fork River meandering past his family's Tennessee farm.

Remember Beltway pundits mocking Gore as a faker for mentioning his childhood days on that very farm? Even as they accepted the "Texas rancher" impersonation of his opponent, who'd never in his adult life lived in a city smaller than Austin, nor, to my knowledge, owned a horse or cow.

There's also a brief clip of the elder President Bush on the stump, shrilly denouncing Gore as an environmentalist crazy.

Mostly, however, "An Inconvenient Truth" rises above partisanship through well-informed and passionately held ideas. Early on, Gore mentions holding hearings on global warming when he first came to Congress, and how bitterly he was disappointed by his colleagues' cavalier dismissal. Silly man, he had an old-fashioned belief in reasoned debate.

Introduced to the concept as a Harvard undergraduate, Gore maintained a layman's interest over the years, watching professor Roger Revelle's hypothesis turn into a frightening reality. "(Global warming) has steadily risen over the last four decades to be, by far, the most important challenge that we (i.e. humankind) face," Gore says. "I believe that it is a planetary emergency, and now the debate is over. The consensus is in. It's real. We're causing it. The effects are really bad. We can fix it. It is not too late."

There's no longer any serious scientific dispute. Gore cleverly dramatizes the reality with a computerized graph illustrating how precisely the cyclical rise and fall in world temperatures over 650,000 years (as measured by studying Antarctic ice cores) track CO2 concentrations in the atmosphere. Then he climbs aboard a hydraulic lifter to illustrate where CO2 levels are today; then raises himself higher still to show where they'll be in 30 years unless mankind adapts. It's visually stunning.

It's also basic physics. Add X amount of CO2 to the atmosphere, and the global temperature will rise in direct proportion. Less clear, given the huge complexities of the world climate system and our imperfect understanding, are the exact outcomes for any given location. But the overall prospects are grim: drought, flood, stronger storms, more frequent tornadoes. Mass extinctions of plant and animal species are a near certainty.

Physics again: Warmer water feeds greater energy into tropical storms. Hurricane Katrina was a wake-up call.

Certain events of very high probability strike us as unimaginable. Mountain glaciers worldwide are melting away at unprecedented rates. Perhaps most critical are the vast ice fields in the high Himalayas, the source of every major river in southern Asia, providing irrigation and drinking water for millions of peasant farmers in China, India and several other countries. As they dry up, famine, pestilence and war will follow.

Can the nations of the world control the manmade causes of global warming in time? Gore professes to think so. Rarely in the history of civilization has so clear a choice presented itself: Reduce the burning of fossil fuels like coal and oil, halt deforestation, limit exponential population growth or leave it to our grandchildren and great-grandchildren to suffer the consequences.

In religious terms, we're desecrating the Earth. In scientific terms, we're conducting a global experiment in climate change with a potentially catastrophic outcome. Failure to act would be madness. Yet some politicians, following a shameful path first blazed by U.S. tobacco companies, cling to irrational doubt. Captive to oil and coal money, one of America's major political parties dabbles in Stalinist-style pseudo-science, denouncing as "elitist" anybody capable of reading the handwriting on the wall.

It's enough to make anybody not consumed with partisanship wish the decent, earnest, intelligent protagonist of "An Inconvenient Truth" were president of the United States.

But that Al Gore appears to have found a higher calling.

Arkansas Democrat-Gazette columnist Gene Lyons is a national magazine award winner and co-author of "The Hunting of the President" (St. Martin's Press, 2000). You can e-mail Lyons at genelyons2@sbcglobal.net.