June 23, 2006 | Just about everything you’ve heard about An Inconvenient Truth is true.

It’s a cautionary documentary about global warming, crammed with distressing facts and disturbing figures, presented in a straightforward fashion that suggests an elaborate Power Point display. It’s also something of a one-man performance film, not unlike Swimming to Cambodia, Monster in a Box and other monologue movies featuring the late, great humorist Spalding Gray. The big difference in this movie is, the raconteur is Al Gore. (Insert joke about comparable stiffness here.) And while he gets a few good laughs – “I used to be the next President of the United States,” he says by way of self-deprecating introduction -- his anecdotes tend to be deadly serious, if not downright terrifying.

Mindful of all that, maybe you’ve already decided you don’t want to see An Inconvenient Truth.

Maybe you should reconsider.

In synopsis, it might sound like the cinematic equivalent of those leafy green veggies that you dutifully consume because your mom always insisted: “They’re good for you!” On screen, however, An Inconvenient Truth proves to be consistently fascinating, intelligently compelling and even, wonder of wonders, unexpectedly entertaining. Unobtrusively directed by Davis Guggenheim, best known for his work in episodic TV (The Unit, Deadwood), the movie rarely strays outside of a lecture hall. But the overall experience is as satisfying as an invigoratingly thought-provoking lecture by a splendidly charismatic college professor.

OK, wipe that smile off your face. Yes, it’s true, “charismatic” isn’t a word frequently used while referencing Al Gore, a fellow often dismissed even by like-minded supporters as a charm-free zone. But just wait until you see him at the top of his game here.

Maybe it’s because Gore has had plenty of time to rehearse and refine his spiel. (He’s given the same multimedia presentation to live audiences throughout the world during the past six years.) Or maybe he learned the true value of loosening up after his classic 2004 guest-hosting stint on Saturday Night Live. Whatever reason, Gore comes across here as engagingly affable, unaffectedly frank – he freely discusses personal tragedies that have shaped his value system -- and entirely comfortable in his own skin. He’s even willing to make fun of himself: At one point, he uses an elevated ladder to make himself a living-and-breathing sight gag to score a salient point.

At the same time, however, Gore never is so personable that he appears to be pandering. And he’s careful not to let his joviality undercut the urgency of his dire warnings. Armed with slides, graphs, charts and time-lapse photography, he is cogent, concise and politely relentless as he offers an array of persuasive evidence – shrinking lakes, diminishing glaciers, receding shorelines, shifting weather patterns, snow-blanketed mountain tops that aren’t nearly so blanketed anymore – to argue that an unforgiving uptick in global warning is not merely an unproven theory, but a demonstrable fact.

A lot of people on both sides of the political divide are going to be arguing about An Inconvenient Truth for a long time. Unfortunately, many of those who’ll speak loudest about the movie will do so without actually seeing it. However you feel about the issues raised by Gore, or about Gore himself, you really owe it to yourself to know what you’re talking about if you’re going to join the debate. "