Jon Snow: Fran, you've done a survey on this very issue at the BBC. Is this one of the findings, that there is in fact an extraordinary balance? Here we have 93 per cent to 6 per cent, and yet many programs do tend to try and put on a balancing voice that says there's no such thing as global warming.

Fran Unsworth: We haven't done a survey about that aspect of it, but George is right. We have a duty at the BBC, because we take the licence fee off everybody, to reflect all aspects of an argument. The issue becomes: What weight do you give to different viewpoints? I absolutely agree with George that I think there was a point when it would seem that once we'd got one person setting out the case for manmade global warming and somebody opposing it, that actually the viewer is probably left with the impression that there is equal weight to these arguments. We have now moved on in our coverage of it. There is now a dwindling band of scientists who don't accept that there is manmade global warming. Our editors and our correspondents have moved on.

Jon Snow: When did this move on happen?

Fran Unsworth: I would say probably in the past 12 months to two years.

Jon Snow: When did you move on George? Twenty years ago?

George Monbiot: Yes, 1985 - but [at the BBC] I don't think it's as long as 12 months or two years. I think it's more like five or six months.

Jon Snow: Do you think New Orleans has been a determinant factor?

George Monbiot: I think it has been one. Also, the complete collapse of the global-warming-denying argument has been another, where there just simply aren't credible scientists left who say it's not happening.

Jon Snow: Elizabeth Palmer, CBS correspondent based in London, how much does CBS do on global warming?

Elizabeth Palmer (correspondent, CBS): I think that Katrina was a turning point. When Katrina was coming in and the levees broke in New Orleans, the story was obvious and the immediate breaking news had to be covered. After a while, when all that had to be said was said, reporters on the ground who I talked to, from various networks, began reaching for other things to say about that situation. And one of the things they reached for was the role of global warming. Beyond that - if this is what's going to come more and more our way with global warming, what can we do about it? It was something that simply was not on the news radar in America, before Katrina - for all kinds of reasons, some of them political.

Jon Snow: Not even after Kyoto?

Elizabeth Palmer: Yes, but it was discussed in terms of politics and American unilateralism, as opposed to a genuine scientific story. I think there has been some very good reporting on the issue of climate change in the United States, and I cite the three-part series in the New Yorker magazine - but much less on television. If it's going to come, and I think it will come, it's going to come as a piggyback on genuine news stories in a more conventional sense. They could be technology, typhoons, health - but that way it's going to creep, finally, onto the screens of the nation.

Jon Snow: Let's go to Greenpeace. Greenpeace made a great thing in their early days of really making headway with specific stories about environmental disaster. Then the terrible disaster of Brent Spar came along, and the media stopped believing Greenpeace. Charlie Kronick, what do you think about the growth of media understanding of climate change, piggybacking, as Elizabeth Palmer put it, on the back of other news stories? Is that going to be the way in which people begin to bring the issue into the media?

Charlie Kronick (Greenpeace UK): I think there's almost an inevitability to that. Part of the problem with climate change is that it has been described as an environmental issue. Jon, despite your enthusiasm for environmentalism, when you get to the hard-news agenda, it tends to be pushed aside by domestic politics, by geopolitics and international conflict.

Jon Snow: I was on the ground in New Orleans, and anyone who was there felt it was global warming. Then we tried to reach out and find out whether it was, and there really is a conflict here. We all agree that hurricanes get worse the hotter the sea temperature, and that the sea temperature is at least one degree centigrade hotter than it was one or two decades ago. The problem then is that there are a whole lot of people who come forward and say, “Hang on a minute. There is a cyclical thing with hurricanes, and that cycle is with us at the moment. We can take you back 50 years, and we'll bring the cycle in again.” And now the journalists were in some difficulty, because you couldn't be sure it really was global warming.

Charlie Kronick: That's the exact same argument that was made by the climate-change deniers - that there was a natural cycle of climate change and you couldn't tell what was happening.

George Monbiot: Charlie, I think you're mixing up two issues here. While we can be absolutely clear that climate change is taking place, we cannot be absolutely clear that any one event is a result of climate change. And it's quite correct in the case of Katrina to say: “Events like this are more likely to happen,” but it's also correct to say: “We don't know whether this one is.”

Jon Snow: Everybody in this room is involved in covering events. And if it's hard to pin the thing on an event, it's very hard for us as journalists to say, “Hey there, folks, global warming!” So are you saying it isn't that you want us to say that it is global warming, but to raise the flag that it may be global warming?

George Monbiot: There are some things that you can very plainly label global warming. For instance, a few weeks ago we had the snow and ice data centre in Colorado saying the Arctic ice is smaller than it has ever been in the whole recorded history of humanity and this is definitely global warming. You can pin that on global warming, there's no trouble with that. Any one weather event you cannot pin on global warming, but you can say: “This is consistent with the predictions made by climate scientists for what global warming is likely to do.” That's the scientifically correct position.

Jon Snow: I want to go to David Hempleman-Adams, who I think has greater chapter and verse on tangible global warming than anybody it's easy to talk to. But let me first go to Bjorn Lomborg, because you actually think that we're right up the wrong tree.

Bjorn Lomborg (author, The Skeptical Environmentalist ): I think the bottom line here is to say: Are we talking about what the media is doing or are we talking about what's actually happening with global warming? Because I definitely disagree with Monbiot on that. I think he's far outside the generally accepted understanding of what global warming is, when he says it's going to wipe us off the face of the earth.

Jon Snow: The issue is not whether you disagree with George's analysis, but whether you disagree with what the media is doing about global warming.

Bjorn Lomborg: Yes, and that's where we have to starting thinking about priorities. There's no doubt that when you look, for instance, at a hurricane, that it's very tempting to say: “That's global warming,” but you've also got to ask yourself, “How much of that …?” Even if we allow ourselves to believe the worst sort of assumptions that, for instance, you see from George Monbiot, that means that within the next 50 to 100 years, the increase in the cost of damages from climate change and hurricanes, is going to account for from 1 to 5 per cent of the total increase. The other 95 to 99 per cent of the cost will come from the fact that we live closer to seashores, that we have much more of value, that we build not according to code and other of those social demands. So what is it that media should be reporting? Should they be reporting: “Oh god, this is global warming, we should do something about it.” Or: “Oh God, we haven't actually dealt with this with our infrastructure, and actually dealing with 95 to 99 per cent of the problems that will come in the years to come.”

Jon Snow: Fran Unsworth, I'm not sure that that has made your job any easier.

Fran Unsworth: No. Exactly the point I was going to make. I think this discussion illustrates very clearly the dilemmas that journalists find themselves in, because of the conflicting arguments that surround this and the difficulties of getting to any kind of way of guiding audiences through it. That's why we have experts, of course, on our staff, to assess the weight of all these arguments. I actually think these points are not in conflict with each other anyway. Clearly something of what's going on in the environment surrounds some of the issues that Bjorn is talking about probably. On the other hand, scientists also are pretty convinced that global warming is caused by manmade factors.