Upbeat and enthusiastic, James Burke will lead you around the world on a journey in time Wednesday, telling you about the weather and its effect on the history of mankind.

He's a charming guide on "After the Warming," which is a good thing, because eventually his route reaches a more ominous topic: the greenhouse effect.

The two-hour special, an unusual combination of fact and futurism, could have been a downer, but it isn't. In fact, it's a fast-paced production that turns out to be visually interesting. And it's full of ideas to mull over and to act on.

Look at "After the Warming" this way: First half, Burke's highly personal narrative about the influence of the weather on the development of civilization. Second half, what civilized man has done to the environment and how things are in the year 2050.

"The trouble with the plain, ordinary greenhouse effect as an issue is that it's been flogged to death and nobody cares anymore," Burke said. "I don't know anybody who'd willingly watch yet more TV coverage of the subject. And made-up minds are closed minds. So the challenge in 'After the Warming' was to open them again."

Burke's show is set in the year 2050, from which vantage he can look at all the preceding eras. Taped footage of Burke at sites around the world is combined with a computer-generated geodesic domed image called the "virtual reality chamber." The laser-projected dome, the stuff of science-fiction movies, was created by Electric Image of London. The result is a stunning special effect, using "digimix" fades that take Burke into and out of on-location footage.

Burke, who used more than 500 studies and source materials to prepare his script, emphasized that "none of this program is fantasy. It is all a result of serious studies. The research took about 10 months. But the filming took very little time -- we didn't have that much money to do it."

To critics who carp about Burke's pop-history and irreverent remarks, he said: "There are two ways to look at this. Either you bring the subject to the attention of a large audience, or you take it seriously and bring it to the attention of a small audience. I always try to do programs like that, especially when they're dealing with subjects that potentially the audience is not interested in."

Burke used a similar approach in "The Inventing of America," a BBC/NBC coproduction offered during the American bicentennial celebration; and two earlier 10-part series, "Connections," which achieved the largest audience to that time for a documentary series during its original PBS broadcast, and "The Day the Universe Changed," which won several awards including a Blue Ribbon from the American Television Society.

Burke begins with the view that "the world's history is the story of weather, for better or worse." His storyline: that a Planetary Management Authority is in its 50th year of operation, having been established, out of necessity, through cooperation of all nations.

Moving around the world in time and space through the computer-generated "virtual reality chamber," Burke takes viewers to the icy shores of Greenland, where he holds the core of a thousand-year-old ice cap that was analyzed to track shifts in the Earth's atmosphere and corresponding climatic changes. In a way, Burke is presiding over a mystery: Why did the ice core show that plants once grew in an area obviously too cold for them? What happened?

He also visits Egypt's Nile Valley in 3000 BC, Thomas Edison's laboratory in New Jersey in 1885, and a South American desert -- formerly a rain forest -- in the year 2050, among other sites. At each location, Burke tells the story of the earth's climate and how mankind's development related to it.

Mike Slee, who directed, said that "some of the computer techniques have never before been used in a film and others are rarely seen by the general public. They create sensational visual experiences that are dizzily real."

Glenn Tolbert of Maryland Public Television produced with Richard Sattin, who with Slee founded Principal Film Company, Ltd., in the U.K. MPT's international partners also included Film Australia and Wiseman, U.K.

But in the second hour of the special, Burke looks at the last part of the 21st century -- the greenhouse years -- and posits how today's weather trends and theories about global environments may unfold. He talks about solar-generated electricity, about agro-forestry, about taxes on the use of fossil fuel and international exchanges of "carbon credits" to cut back on gas emissions and improve economies.

At the present time, cutting back on emissions believed to cause global warning is already underway, at least in some countries. In fact, preparing for an international climate conference that met two weeks ago in Geneva, the World Meteorological Organization circulated a draft declaration reflecting the commitment of European governments to stabilize the production of such gases.

But the United States, whose per capita emissions of carbon dioxide are more than double those of Japan and France, responded with warnings and weakening amendments as long as the declaration itself. The Bush administration, skeptical that global warming is scientifically valid, refuses to take action that threatens the way the United States generates energy and runs its economy.

Still, it is an energy-efficient conventional-energy exhibit house in Pittsfield, Mass., built by GE Plastics, that Burke presents when he discusses technological advances and alternative energy sources. And it is footage of a private home in Hawaii that he shows to illustrate a home whose roof is equipped with solar photoelectric cells.

That's because "it rains all the time in England," he said. "Actually, the Dutch and the Danes are very far ahead on things like wind power. There's not too much solar power in Europe because of the weather."

A print journalist who began his television career in 1965, Burke said that he is interested in alternative energy sources, but admitted that he hasn't done much to modify his own lifestyle except to give up eating red meat.

"My own lifestyle is extremely English and therefore extremely limited," he joked.

He also credits the Dutch for commissioning a study on the idea of planetary management.

"It's a kind of basic background scenario, and the key thing about that scenario is one that gives you energy and independence," he said. "People are already beginning to talk about energy independence. One is even now beginning to feel that in the media."

Burke's special has included a rather gloomy vignette featuring a small family leaving its apartment. He explained: "In Britain there was a competition for people to make advertisements, commercial advertising agencies, and we were able to get the archives of those things. We used one that was specifically meant to say, 'Do something about this or we'll leave it to the children.'"

Surprisingly, Burke's unusual presentation also comes off as fairly optimistic. By 2050, mankind has heeded the warning and cleaned up what's left of the environment. Because renewable energy sources such as solar power have been tapped, power is no longer related to how much oil or coal a country has.

There is life on Earth, even after decades of selfishness, although the style is not quite the same as in the ruinous, carefree days. There are trees again, and a return to small towns. People work at home, using computers. Countries have retooled their industries to make them more efficient and compete with the Japanese in the marketplace. Small, struggling nations have become less dependent on western handouts by trading their "international carbon units" to bigger, energy-consuming countries for improved food, medical care and educational opportunities.

These things could be done with or without the doomsday greenhouse scare, of course, but in Burke's scenario, the fear of devastation was necessary to get them accomplished.

"We don't quite solve the problem, but it is an optimistic view," Burke agreed.

And to those whose view is darker?

"The optimist says we might as well solve the problem; the pessimist jumps out the window. Which do you want?"