The Day After Tomorrow opens today, a sound-and-fury disaster flick that casts global warming in the same bad-guy role as the evil space invaders of director Roland Emmerich's previous offering, Independence Day.

The threat this time isn't monsters but molecules – the carbon dioxide and other greenhouse gases gathering in the atmosphere as a result of fossil-fuel burning, land-use changes and other human deeds. While earthling grit eventually beat back the alien beasts in Independence Day, the outcome of the war of the warming – the real war, not the cinematic fantasy – is much less certain.

But there's another difference: Independence Day didn't trigger a hailstorm of news releases from pro- and anti-space creature groups. The Day After Tomorrow, on the other hand, has already become an environmental springboard – or dartboard, depending on one's perspective.

20th Century Fox

While the real effects of global warming won't be as abrupt or dramatic as depicted in The Day After Tomorrow, its point about global warming is based on science, experts say.

"Nobody talked about science and policy with Independence Day ; there was no political spin about aliens," said Dr. Benjamin Preston, an environmental biologist and senior research fellow with the nonprofit Pew Center on Global Climate Change in Washington, D.C.

Environmental groups and many scientists agree with Dr. Preston that The Day After Tomorrow, while scientifically silly, will remind people that global warming is a real threat – not in the sudden 9-11 sense depicted on the screen, but serious nonetheless.

"Just about everything in [the movie] can't occur because of the fundamental laws of physics," Dr. Preston said.

But it will get lots of people talking again about the hard choices posed by a changing climate, he added, probably for the first time since the Kyoto climate treaty in 1997.

Some with different viewpoints say they're being dragged rather than drawn to see The Day After Tomorrow. For those who oppose Kyoto and its call for mandatory curbs on greenhouse gas emissions, the movie is just a big-budget distraction.

"I'm being forced to go watch it, reluctantly," said Dr. H. Sterling Burnett, senior fellow with the National Center for Policy Analysis, a Dallas think tank that backs private-sector action on public problems. "I don't really think it's going to have much of a public impact. I think it's much ado about nothing."

Dr. Burnett compared the new movie to another eco-catastrophe film, 1971's Silent Running. In that one, Earth's forests are all destroyed and plants survive only in greenhouses floating in space – a good movie, Dr. Burnett said, but it didn't spark a global save-the-trees movement.

But there's already evidence that The Day After Tomorrow is plowing fertile ground with the public.

On Thursday, Yale University's School of Forestry & Environmental Studies published a national poll finding that 70 percent of Americans think global warming is a somewhat or very serious problem. The poll also indicated that 55 percent of Americans believe "the scientific evidence is in" about global warming.

Global Strategy Group, a polling firm working for Yale, questioned 1,000 adults selected at random from April 26 to May 3, before the movie's publicity onslaught.

"The bottom line is that a vast majority of Americans say the science is clear on global warming and that it's time to take action," said Daniel Esty, director of the Yale Center for Environmental Law and Policy. "We don't need Hollywood hype to get the public focused on global warming."

What is global warming?

Global warming is the rise in worldwide average temperatures being attributed to human influences, chiefly emissions of heat-trapping gases. The average at the Earth's surface rose by an estimated 1 degree during the 20th century alone. Concentrations of carbon dioxide in the atmosphere were steady at about 280 parts per million from A.D. 1000 until 1750, the start of the Industrial Revolution. Since then, they have risen to 368 parts per million, a 31 percent increase.

SOURCE: Intergovernmental Panel on Climate Change

Impending change

There are signs of policy changes, too. Russia, after zigzagging for months, now says it will ratify the Kyoto treaty, a move that would bring the pact into effect even without U.S. approval. And in October, the McCain-Lieberman Climate Stewardship Act, which would cap U.S. emissions, got 43 Senate votes, more than expected. Environmentalist are pushing hard to raise that number for a second vote not yet scheduled.

"On the policy side, it's not as bad as people might think," said Eileen Claussen, the Pew climate center's president and assistant secretary of state for the environment in the Clinton administration.

The scientific gist of The Day After Tomorrow is that greenhouse gases trigger an abrupt global response, causing tidal waves, tornadoes and, oddly enough, a sudden ice age. Scientists do believe that global warming could cause abrupt climate shifts – but that means over decades, not days.

Still, the notion that emissions are perturbing the climate wasn't dreamed up on a sound stage, scientists say. Theories that have held up under tough scrutiny are now bolstered by real-world observations, they say, from melting glaciers to shifting species.

The basic principle is simple: Carbon dioxide and other gases trap heat in the atmosphere. The Earth itself is proof; without the greenhouse effect, this would be a cold and lifeless planet.

Since that is true, most climate scientists say increasing the amount of heat-trapping gases should also increase the amount of heat. That's the premise that researchers have been testing for decades.

In its most recent comprehensive report in 2001, the Intergovernmental Panel on Climate Change, a United Nations-created body that serves as the world's clearinghouse on global-warming science, said the 1990s saw the highest recorded levels of greenhouse gases in the atmosphere.

It's likely, the panel said, that that decade was also the hottest in 140 years, and that 1998 was the hottest year. The thermometer rose more in North America in the 20th century, according to the scientists, than in any century for the past 1,000 years.

Humanity's effect

There's ever stronger evidence, the scientists said, that much of that warming was people's doing – burning coal and oil, draining wetlands and a hundred other staples of the world economy.

Research since then hasn't changed the fundamental conclusions, said the Pew center's Dr. Preston. Scientists have tried to explain the rise in temperatures without human influence, he said, "but they've failed time and time again."

There are scientific dissenters, however, such as Dr. John R. Christy, director of the Earth Systems Science Center at the University of Alabama in Huntsville. Dr. Christy, one of more than 100 lead authors of the climate change panel's 2001 science report, has challenged the temperature data that led to the panel's findings.

But some of those who object to the proposals to address the problem, such as a turn away from coal use, have stopped hoping that more science would disprove global warming.

"Even skeptics admit some warming, now into the future, maybe as high as half a degree," said Dr. Burnett of the National Center for Policy Analysis. Those who think the whole phenomenon is made up, he said, "are now even a smaller minority than they were before."

E-mail rloftis@dallasnews.com