If you're planning on seeing "An Inconvenient Truth," there are two things you need to expect: plenty of Al Gore and plenty of Al Gore's lecture on global warming.

However, this is not the Al Gore you may remember from the 2000 presidential election. The near-robotic stiffness, the hope-crippling unelectability and the "lock box" are all gone, replaced by a much more genial attitude and — surprise, surprise — an actual sense of humor.

But for all the laughter the new Gore inspires, he never wavers from his goal: to illustrate the threat he perceives is posed by global warming. He comes with all kinds of evidence, and it's all compelling.

It's true that a celluloid Gore appearing in several cities simultaneously is a more effective way of communicating the message than the real Gore going from city-to-city. But during the lecture segments — Gore calls it a "slide show," but his presentation has all the data, charts and novice Keynote (Apple's PowerPoint equivalent) skills of a collegiate lecture circa 2006 — you may be moved to ask, "Why am I watching this in a movie theater?"

The biographical segments raise further questions about the film's purpose. It's rather thoughtful of Guggenheim to provide a backward glance at Gore's inspiration for taking up the environmentalist torch, but this also creates an obnoxious duality within the film, making it difficult to determine whether "An Inconvenient Truth" is about the global warming crisis or the life of Al Gore.

Looking past the lecture aspect, Gore's matter-of-fact presentation is startling. The extending screen and rising platform he uses to illustrate projected skyrocketing atmospheric carbon dioxide levels is played for humor, but the chart of corresponding rising temperatures is no laughing matter.

The photographic evidence of receding glaciers and ice caps provides the visual punch that graphs and data lack. Shots of the disappearing snow atop Mount Kilimanjaro play like a globally catastrophic equivalent to the before-and-after photos in a weight loss infomercial.

The film's many projections — from shifting weather patterns to devastatingly high sea levels — might induce scoffs from those Gore calls "the so-called skeptics."

Most likely, those people won't be attending the film. If the crowds at the Michigan Theater last week were any indication, the audience's reaction is more likely to be manifested in hisses — at images of President Bush.

Though it's full of incendiary information, "An Inconvenient Truth" is also full of to-the-choir preaching that is unlikely to convert anyone who isn't already convinced of global warming's existence.