As global warmingists breathlessly await a new report from the United Nations about the imminent doom of our planet, and Democrats convene highly publicized panels in Congress to discuss how only they can save the world, two well-known skeptics were guests on “Hannity and Colmes” Tuesday.

What ensued could only be improved upon if the discussion was to be required viewing all over the country – especially in public schools – as a rebuttal to Al Gore’s schlockumentary “An Inconvenient Truth.”

Fred Singer of the University of Virginia began:

Well, the climate is warming. That's what the temperature indicators show or the thermometers show this. But the cause of warming, that's another story. It could either be natural, as we think it is, or it could be manmade. And we find that there is really no evidence to support the manmade hypothesis.

Dennis Avery, Singer’s co-author of the new book on the subject “Unstoppable Global Warming,” then gave some historical perspective:

The Romans wrote in the 1st century about growing wine grapes in Britain. Then, during the Dark Ages, it was too cold. During the medieval period, the Britons themselves wrote about growing wine grapes in Britain. And then, for 650 years, during the little ice age, it was too cold.

After 1950, they started trying to grow wine grapes again in Britain. They're now up to two years out of 10, with a little help from some tricky hybrids. So this tells us, a, there's a cycle and, b, the temperatures today aren't yet as warm as they were 650 years ago or 2,000 years ago.

Hannity asked if warming is tied to humans. Singer chimed in:

There has never been a case of human activity causing a global warming. And, of course, sea levels have been rising since the end of the last ice age. In fact, sea levels have been rising about 400 feet, since about 18,000 years ago.

After Hannity asked about Gore’s contentions, Singer replied:

I don't think he thinks he's lying, but I don't think he understands the problem really well. For example, when he talks about glaciers melting, of course they're melting. You would expect them to melt when the climate is warming. But that doesn't tell you why the climate is warming…He's confusing consequences and the cause. He's making a logical error.

Colmes entered the discussion by asking if the recent increases in CO-2 aren’t “incontrovertible proof that the behaviors man has led to what we're talking about here.” Avery responded:

Not at all. In the 1980s, we dug up long ice cores from both Greenland and the Antarctic. They showed a moderate, natural, 1,500-year cycle. We've had 600 warmings in the last million years. And the ice cores and the sea bed sediment show this. And none of the past has found CO-2 coinciding with temperature change.

In fact, Mr. Gore, in his Antarctic scenario, says temperature and CO- 2 have moved radically and together through the last four ice ages, and that's true. What he doesn't tell us is that the temperatures changed 800 years before the CO-2 levels.

Singer also had an opinion on this CO-2 issue that seems lost on all of the global warmingists:

Well, CO-2, of course, is not a pollutant. It is a naturally occurring gas in the atmosphere. In fact, it's essential to life. It's what all plants use in order to grow. Without CO-2, there would be no life on Earth. So let's get that very clear: It is not a pollutant.

It has increased. And it is undoubtedly the case that the human activities have led to the increase. But that doesn't prove it's the cause of warming. You see, it's just a correlation. And, for example, during much of the last century, the climate was cooling, while CO-2 was rising, so how do you explain that?

The global warmingists don’t explain that, and the media don’t question them about it. In fact, that’s the point.

What follows is a full transcript of this segment.

HANNITY: Scientists from the United Nations' climate panel are gathering in Paris to determine the effects of global warming. Their conclusions will be released later this week. But is the growing panic over global warming based on fact or fiction?

Joining us now from the Hudson Institute, environmental economist Dennis Avery and physicist and professor from the University of Virginia, Fred Singer is with us.

Guys, thank you both for being with us. Are we being told the truth about global warming, Dr. Singer?

FRED SINGER, UNIVERSITY OF VIRGINIA: Well, the climate is warming. That's what the temperature indicators show or the thermometers show this. But the cause of warming, that's another story. It could either be natural, as we think it is, or it could be manmade. And we find that there is really no evidence to support the manmade hypothesis.

HANNITY: Dennis Avery, is that your conclusion?

DENNIS AVERY, "UNSTOPPABLE GLOBAL WARMING": We've got an interesting historic perspective. The Romans wrote in the 1st century about growing wine grapes in Britain. Then, during the Dark Ages, it was too cold. During the medieval period, the Britons themselves wrote about growing wine grapes in Britain. And then, for 650 years, during the little ice age, it was too cold.

After 1950, they started trying to grow wine grapes again in Britain. They're now up to two years out of 10, with a little help from some tricky hybrids. So this tells us, a, there's a cycle and, b, the temperatures today aren't yet as warm as they were 650 years ago or 2,000 years ago.

HANNITY: Professor Singer, I know they're claiming on the left, and Al Gore leading the way, that the polar ice caps and glaciers will melt and sea levels will rise, et cetera, et cetera. They claim that parts of that is actually true, but there are also other ice caps, as I understand it, and scientists are saying, that are actually thickening here.

Has human activity ever been the cause of global warming? Because it's now seemingly, in the political world, becoming conventional wisdom.

SINGER: There has never been a case of human activity causing a global warming. And, of course, sea levels have been rising since the end of the last ice age. In fact, sea levels have been rising about 400 feet, since about 18,000 years ago.

HANNITY: Can I ask a question? You've heard Vice President Al Gore. I don't know if you've taken the time to go see his movie.

SINGER: Of course.

HANNITY: Is he lying to the American people? Is he politicizing this topic for some type of political agenda?

SINGER: I don't think he thinks he's lying, but I don't think he understands the problem really well. For example, when he talks about glaciers melting, of course they're melting. You would expect them to melt when the climate is warming. But that doesn't tell you why the climate is warming.

COLMES: Hey, Dennis Avery, in terms of politicizing -- yes, go ahead.

SINGER: He's confusing consequences and the cause. He's making a logical error.

COLMES: Let me go to Mr. Avery if I can. According to this new U.N. report that is being criticized by you and others, it does say that, before the industrial revolution, levels of CO-2 were 280 parts per million. Today there are 380 parts per million, an increase of CO-2 in the atmosphere, which they specifically put on the industrial revolution, with those numbers to prove it. Is that not incontrovertible proof that the behaviors man has led to what we're talking about here?

AVERY: Not at all. In the 1980s, we dug up long ice cores from both Greenland and the Antarctic. They showed a moderate, natural, 1,500-year cycle. We've had 600 warmings in the last million years. And the ice cores and the sea bed sediment show this. And none of the past has found CO-2 coinciding with temperature change.

In fact, Mr. Gore, in his Antarctic scenario, says temperature and CO- 2 have moved radically and together through the last four ice ages, and that's true. What he doesn't tell us is that the temperatures changed 800 years before the CO-2 levels.

COLMES: Professor Singer, we are seeing the CO-2 levels, though, rise in conjunction with the industrial revolution. How you can you discount the amount of pollution that's gone into the atmosphere since around 1900, in conjunction with manufacturing and what we have done to the environment? How you can discount that?

SINGER: Well, CO-2, of course, is not a pollutant. It is a naturally occurring gas in the atmosphere. In fact, it's essential to life. It's what all plants use in order to grow. Without CO-2, there would be no life on Earth. So let's get that very clear: It is not a pollutant.

It has increased. And it is undoubtedly the case that the human activities have led to the increase. But that doesn't prove it's the cause of warming. You see, it's just a correlation. And, for example, during much of the last century, the climate was cooling, while CO-2 was rising, so how do you explain that?

HANNITY: Professor Singer, we appreciate your wisdom. Thank you for being with us. Dennis Avery, thank you for being with us. I hope Al Gore is watching.

—Noel Sheppard is the Associate Editor of NewsBusters.