This past weekend concerts took place around the world to focus attention on the problem of global warming, which former U.S. Vice President Al Gore says is the greatest single threat facing humankind today.  Most of the world's scientists agree that it is a problem and that it is largely caused by human use of fossil fuels, which produce so-called greenhouse gases that trap the Earth's heat.  Al Gore and scientists who wrote the United Nations report on climate change say the debate is over and the time has come to act. But some prominent climate scientists are objecting to that, claiming that the debate has yet to even begin. VOA's Greg Flakus recently spoke to one of them and filed this report from Fort Collins, Colorado.

In Al Gore's movie, An Inconvenient Truth, the dangers presented by global warming are shown in graphic fashion, with photos, maps and charts. In his view, there is no time to lose in addressing global warming.

GORE: "That is what is at stake, our ability to live on planet Earth."

The poster and cover art for the movie show a huge hurricane coming out of a smoke stack. But that image and much of what Al Gore presents in the film is rejected by one of the most respected men in the field of climate studies in the United States.

William Gray, 77, the principal force behind the annual hurricane forecasts done by Colorado State University's School of Atmospheric Science, has little good to say about Gore and his movie.

"He is making statements that I could never make. He is making assumptions that are just not true. I think there are many factual errors in his movie," he said.

Gray rejects Gore's assertion that hurricanes are becoming more frequent and more intense as a result of global warming. A number of other scientists, even some who support Gore's position in general, have also questioned some of the claims made in the movie.

But not William Gray. He does not dispute that the world is warming, but he does not see it as a crisis and he does not think emissions of CO2, methane and other gases have much to do with it.

"Yes, we have seen some global warming. I think it is primarily natural due to the global ocean circulation features," he added.

Gray says the current warming trend is part of a natural cycle and that the world may soon enter a cooling phase.

The Intergovernmental Panel on Climate Change (IPCC) recently reported that climate change is accelerating even faster than had previously been predicted, adding to the urgent need to take action. But Gray and other critics say these predictions are based on unreliable computer models. He says the IPCC has a political agenda and that skeptics are kept out of the discussion.

"The IPCC and all these reports, I have been over 55 years working in the field and they never have come to me one time," he said.  "I have just been isolated and I know other colleagues of mine, who I respect for their knowledge. They never consulted them either. If they know how you think, they just leave you alone and go on."

IPCC scientists reject such characterization of their consensus view and defend computer modeling as a way of understanding how greenhouse gases are affecting climate.

Gray believes the cutbacks in fossil fuel use advocated by the consensus scientists would hurt the economies of the United States and other industrialized nations and, in the end, do little or nothing to stop global warming. He says all the attention focused on global warming is distracting people from the world's real problems.

"We have so many other important problems around the world that are much more critical," he explained.  "For instance, poverty, AIDS, terrorism, all these problems we have in the world. To me this global warming is sort of a red herring. They have been saying it is the greatest problem facing mankind now. That is a gross exaggeration."

William Gray plans to write a book to refute Gore's and other global warming activists' arguments. He says he and other skeptics have been shunted aside and dismissed as "global warming deniers." Critics also claim the skeptics are financed by large oil companies, but William Gray says he has never taken any money from the energy industry.

While he may not have convinced some of the scientists who believe in human-induced global warming, he may yet have a chance to make his case. Some scientists from the global warming camp are now saying that debate should be allowed. As Gray and other skeptics have argued, science is advanced through constant questioning and testing of hypotheses, not by consensus.