Despite the sensational headline (“Day After Tomorrow” Ice Age “Impossible,” Expert Says) — eagerly parroted verbatim by Drudge as propaganda fodder — National Geographic’s interview with Worldwatch Institute senior editor Tom Prugh is actually a fairly balanced assessment of global warming fact and fiction in The Day After Tomorrow, which opens tomorrow:

So should we brace ourselves for another ice age?

No, I don’t think so. The scenario in the movie is fictional. Like some other Hollywood movies that claim to be based on true stories, there’s a kernel of truth that is then pumped full of steroids and given cosmetic surgery.

But is global warming real?

The overwhelming scientific consensus is that global warming is real, and that it’s upon us now. In the last century, the average temperature of the Earth has warmed roughly 1° Fahrenheit [0.56° Celsius]. That means an enormous additional amount of heat energy has been built into the system, and there are serious consequences to that warming.

What role does human activity play in global warming?

The atmosphere of the Earth is like a blanket that traps heat. It keeps the temperature at the surface of the Earth about 50° or 60° [Fahrenheit/28° or 33° Celsius] warmer than it would be otherwise, which is great because it makes the world a pleasant place to live. But humans have been adding to the gases that help trap this heat.

We’ve been adding to the stock of carbon dioxide in the atmosphere by taking coal, oil, and natural gas out of the ground and burning them as fuels. Combined with deforestation, this has added around a third of the amount of carbon in the atmosphere. …

How realistic is this movie?

It has a kernel of truth, although it has been “Hollywoodized.” There is evidence that abrupt climate change has happened a couple of times in the last 13,000 years, but it’s never happened in a few days, as it does in the movie. That’s completely impossible.

What is the ocean conveyor belt referred to in the movie, and what is its importance to the Earth’s climate?

It’s the system of currents that flows around the oceans of the world and carries heat from the tropics to the northern latitudes. There is evidence that the North Atlantic branch of the current has failed in the distant past—8,200 and 12,700 years ago—causing a great cooling of the climate.

In the movie, the influx of fresh water, caused by the melting of a massive ice sheet, changes the salinity of the oceans, shutting down the Gulf Stream. Could that happen?

In theory, that is realistic. Salty water is heavier than fresh water. When the cold, salty current reaches the northern latitudes and gives out its heat, the current actually sinks and flows back along the bottom of the ocean toward the tropics.

When then there’s a lot of fresh water added to that current, it may stop flowing, because it’s not dense enough to sink anymore. In the past, retreating glaciers dumped enormous amounts of fresh water very suddenly into the North Atlantic, and the currents stopped.

What about the superstorms depicted in the movie, which form like hurricanes over North America, Europe, and Asia? Are they realistic?

No. Hurricanes form over waters and tend to break up and dissipate when they reach shore. They can’t get the energy to keep going anymore.

One of the effects created by the superstorms in the movie is the pulling down of supercool air from the troposphere that freezes people in a matter of seconds. There is nothing that suggests this could happen.

Could another ice age happen?

It’s unlikely. Even if there were a continued influx of fresh water that weakened or stopped the North Atlantic current, any cooling effect that might create would be swamped by the warming that would continue to happen in the meantime.

But if abrupt climate change has happened in the past, before the industrial revolution, isn’t this just part of a natural cycle that is, in a sense, inevitable?

Certainly the climate has, to some extent, a mind of its own. But that’s not to say we’re not having an influence on what the climate is, what it does, and how it behaves.

We’ve taken a great deal of carbon that used to be locked up in the Earth in the form of coal and undisturbed oil and natural gas and released it into the atmosphere. That carbon hadn’t been there in the atmosphere for millions and millions of years.

It’s simply naive to think that’s not going to have an effect on the climate.

For the record, the only thing Prugh says is “impossible” is abrupt climate change happening in “a few days.” As for the possibility that it could happen on a more realistic timetable, he states, “I don’t think anyone thinks abrupt climate change is likely any time soon, but the probability is not zero.” And he certainly never says that an “ice age” is “impossible” — just that it’s “unlikely.”

He concludes: “I would urge people to go see the movie. I thought it was a lot of fun. I would also urge them to drive to the movie theater together with a few friends [to conserve gasoline and put less exhaust into the atmosphere] and turn out all the lights in the house before they leave.” Heh.