Understandably, Davis Guggenheim’s riveting global-warming documentary An Inconvenient Truth leaves a number of questions hanging, including the biggie: Will the approaching environmental catastrophe it warns of be averted, or will we soon witness places like the Outer Banks, Manhattan, the Bay Area and Bangladesh sliding beneath the waves with the same kind of dumbstruck horror provoked by the TV images of Hurricane Katrina?

A more immediate question, though, concerns the film itself: Will it change enough minds to change public policy in the United States, the one country so selfishly resistant to international cooperation on the environment that it sometimes seems to harbor a planetary death wish?

Success on that level, which would mean attracting millions of viewers and then catalyzing them into action, seems almost inconceivable. Drawing large numbers of moviegoers to what’s basically a 90-minute science lecture would be tough even if it were presented by Angelina and Brad in thongs. But if it’s presented by Al Gore, the pickled Frankenstein of Election 2000, whose negative charisma and blundering campaign delivered the republic into the hands of history’s worst president–what hope does that film have of waking America from its climatic coma?

Well, guess again. If any modestly budgeted independent film could shift the environment back to the nation’s front burner, An Inconvenient Truth looks to be the one.

Since opening nationally a couple of weeks ago (it previously made well-publicized splashes at the Sundance and Cannes film festivals), the film has taken off like a box-office skyrocket, and already bids to claim the season’s documentary earnings record. Last summer we had cuddly penguins schlepping across the Antarctic ice shelves. This year it’s drowning polar bears and Gore probing the alarming deterioration of those very same shelves. Talk about polar shifts.

Among the various factors that contribute to the film’s improbable success, three stand out immediately. First is Gore himself, who–believe it or not–is human, funny, limber, articulate and eloquently, believably impassioned: everything he tragically wasn’t six years ago.

Second, in mounting what’s basically a cinematic version of a slide lecture that Gore has delivered over the years at countless locations around the world, Guggenheim and his collaborators create an exceptionally fluid and inviting stylistic package. This may be more Madison Avenue than M.I.T., but as for putting across science and statistics to a diverse, image-besotted public, it’s commendably deft, clear and compelling.

Third, and most important, is the message itself. Gore reaches back to his college days to explain that it was one of his Harvard profs, Roger Revelle, who kindled his interest in global warming. Revelle was one of the first scientists to measure and study the effects of the increase of carbon dioxide emissions on the atmosphere, and his worrisome findings and all-too-accurate predictions gave Gore a cause that he took to Congress in the 1970s. He figured his colleagues there would be as concerned as he was, and move to act. Right. Decades later, he feels like he’s failed to get the message across, so he gives it one more try. Will we listen?

The message is both essentially simple and startlingly dramatic. The premise: Increases in the release of CO2 and other gases trap the sun’s heat within a thickening atmospheric blanket, and as a result, temperatures go up and up. There’s no questioning the science of this, Gore says: The correlation is direct and conclusively established.

In the United States, the burning of fossil fuels contributes most to the climatic change. And while the process has been going on for many decades, in recent years its effects have leapfrogged at an astonishing rate. You’ve probably seen some of the evidence in occasional newspaper photos, but when Gore assembles pictures and data from around the world, the cumulative effect is sobering indeed. The fabled snows of Mount Kilamanjaro receding so rapidly that they won’t exist a few years hence. Glacier National Park losing the reason for its name. Age-old glaciers melting like popsicles in Europe, Tibet, South America. Arctic permafrost turning to slush. The ice cap at the top of the world crumbling so fast that polar bears drown after swimming 60 miles in search of solid ice.

This isn’t just the loss of snowy scenery. It’s part of an enveloping global pattern of climate change that engenders deserts and droughts and famines, kills off species at staggering rates, and helps spread diseases like SARS as well as insects that endanger humans, crops and trees.

And then there’s the havoc played with the weather. One of the film’s most eye-popping stats is that all 10 of recorded history’s hottest years occurred in the last decade and a half. The most recent was 2005, of course, the year that the ongoing surge in hurricanes’ frequency and ferocity dealt the United States its most spectacular blow yet.

Gore persuasively chunks claims that such changes are “cyclical” with evidence that nothing comparable to the recent spike in temperatures has happened in the last 650,000 years on earth. And while the changes noted above may be gradual, he saves his most serious speculative worries for a couple of scenarios that could be anything but.

Western Antarctica and Greenland already are melting fast enough that one–or both–could collapse into the ocean. If that happens, it would likely raise sea levels several feet in a relatively short amount of time. This is where we hit the kinds of doomsday visions suitable to Hollywood horrormeisters: entire cities swamped by rising tides, the widespread submersion of luckless lowland locales like Florida and Holland, refugees on the Indian subcontinent numbering upward of 100 million.

Here the mind balks, and we wonder if we’re being oversold. Perhaps. But what if Gore is right and we may have only 10 to 20 years to reverse the pattern? One of Gore’s most astute comments is that, confronted with such information, people tend to go from denial (there is no crisis) to despair (there is no solution) in a trice, without stopping in the middle to ask about effective action. Gore is all about effective action.

He reminds us that America has acted before, rapidly and effectively, to improve the environment. The beneficent effects of the Clean Air Act can be seen in ice samples taken in Antarctica. As for the Bushite claims that limiting CO2 emissions and similar measures would “hurt the economy,” Gore shows that the auto industries in countries that enforce strict emissions controls are far outperforming America’s sad behemoth of an industry in the global marketplace. In fact, led by the insurance industry with its understandable alarm over the stupendous costs of changing weather patterns, American business, Gore suggests, could find it to its advantage to help catalyze the demand for change in U.S. policy.

Yet, in various ways, such change will ultimately come down to individuals. Gore’s informational enterprise has a Web site (www.climatecrisis.net) and the film points out many means–from using energy-efficient light bulbs to hybrid-fuel cars–by which average citizens can contribute to easing global warming. And while some of the important actions to be taken must occur on the collective front, including regulatory legislation and joining in international efforts like the Kyoto Protocol, even these will finally depend on individual citizens manifesting the resource that Gore sees as most crucial to environmental salvation: political will.

Gore’s faith in our capacity for self-rescue via democratic action is touching, to be sure. I’m a lot less optimistic, frankly. Yes, three decades ago a broadly popular environmental movement arose and our lawmakers enacted legislation to clean up our air and water and safeguard other resources. What’s changed since then is not so much that such laws have been undermined and needed new ones have been forestalled due to myriad economic and political pressures–although both things are true–but that the United States has undergone a crucial shift in what might be called our collective psychological environment.

By my not entirely scientific calculations, it was circa the onset of the Reagan administration that many Americans traded a rudimentary engagement with unmediated reality for an addiction to feel-good fantasy as contrived and delivered by an increasingly sophisticated alliance of large corporate and right-wing political interests. The result is something that undermines the single most critical component in a democracy: Many people don’t vote on the basis of self-interest because they can’t identify it. Reality itself has grown malleable. This may be a “soft” Orwellianism, but it’s Orwellian nonetheless. Up is down. In is out. Lies are truth. John Kerry is a Vietnam War shirker, George W. Bush a hero of the same fight.

Telling us that it is possible to correct bad habits, Gore recounts the family tragedy that turned his father away from growing tobacco, and he shows us a magazine ad from the time when the U.S. Surgeon General’s Report linked smoking to lung cancer: “More Doctors Smoke Camel.”

Likewise, the huge corporate interests that generate our culture’s politicized fantasy have done a remarkably good job in convincing at least half the country that, according to many “experts,” global warming is “unproven” or “controversial.” What chance does a little indie film have against this pervasive climate of disinformation? To put it purely in movie terms, though An Inconvenient Truth‘s early earnings were impressive, they were dwarfed by those of The Omen, which tells us that recent natural disasters are due to the approach of the End Times.

Actually, as Gore has said in The Nation, his film’s effort at moving public perceptions toward a tipping point is being assisted by several other recent developments, including that some prominent evangelical Christians have taken up the green banner in the name of planetary stewardship. He’s right that such changes are critical. If his film turns out to be merely a blue-state, art-house phenomenon–a summertime Brokeback Mountain–it will be merely a brief candle in a bitter wind.

Only by reaching all the way across the cultural/political spectrum does it stand a chance of significantly affecting public policy. But why shouldn’t that happen? Is saving the planet from man-made disaster really that “controversial”?