Marlo Lewis, senior fellow at the Competitive Enterprise Institute—a Washington, D.C., think tank—specializes in environmental policy and questions Gore's global warming claims. Recently, he wrote A Skeptic's Guide to an Inconvenient Truth to rebut Gore's research.

Marlo says An Inconvenient Truth makes it seem like we can reasonably expect the sea level to rise 20 feet in our lifetime or the lifetime of our children. "This is science fiction," he says.

Americans also shouldn't worry about environmental changes in Greenland or Antarctica, he says. "If you look at the actual loss of ice in Greenland and what it translates into, in sea level rise, it's about one inch over a century," he says. "Several studies show that the entire continent of Antarctica is actually gaining ice mass. That's an inconvenient fact that is nowhere mentioned in the film."

Marlo believes that Gore's film is an attempt to "scare us green." "He wants us to be very frightened of global warming," Marlo says. "The warming that we've seen over the last 30 years is constant and modest, and in all likelihood, will give us a modest amount of warming in the next century. And, therefore, it's nothing to be afraid of."