 You've been visiting the world's ecosystems for over 50 years now. What changes are you seeing in places that you're going back to like the Great Barrier Reef? Just recently I've been in Borneo and I've been going to Borneo for 50 years or so. And it's very evident there, particularly if you take fly by air, a helicopter journey across the width of Borneo, or Secretary of the Week anyway, is very revealing. The Kenbanatangu River, which used to be a really wild area when I first went, there's a fringe of about, I suppose, a couple of hundred yards on either side of the river where there's riverine forest. And then beyond there, there is uniform oil pumps. As you talk to scientific experts, what was it that convinced you that humans are causing these kind of changes, climate change? Oh, well I think you put your finger on it. It's when you talk to the experts, because by and large, looking for human effects on the natural world, you just don't go out and walk into the bush and say, oh yes, that's human effects. You need much more solid observations than that, and particularly observations through time. And what convinces you is measurements of the kind of component gases in the atmosphere, for example. And when you've got records, as we have in Europe, going back to the 18th century, at the beginning of the Industrial Revolution, and you suddenly see the figure of CO2, for example, and other gases too, steadily increasing. And if you plot against that population as well, you have not much doubt that human beings have had an effect upon the atmosphere. Based on what you've seen and talking to the experts, how do you think that life on Earth will be affected if we don't resolve the climate change problem? Well, I think one of the most sensitive places is here in eastern Australia, in Queensland. The two effects of climate change that I think we can be absolutely certain about beyond any question is that the temperature of the ocean is rising and the acidity of the ocean is rising. And work that's been done here in Heron Island and elsewhere makes it absolutely clear as to what the effect of those two factors will be upon coral Earth. And the time passing and increasing those figures will lead to disaster unless something is done. And there are those who say that there's almost nothing that can be done, except, and my response to that is that it'll be worse if we do nothing. There's not an excuse for doing nothing, saying you can't stem it. You can stem it down, that's for sure. And it'd be really culpable if we don't. Are you optimistic that we can make the changes we need to avoid the worst impacts? I have no real evidence to feel one way or the other. It's only gut feeling. And gut feeling is not a good way of going around and judging things. All I know is that a responsible biologist has to say what these facts are and to take every chance of influencing those people who can change or can influence those circumstances. And those are primary politicians. I guess that brings an important question is what advice would you give scientists and experts who are trying to communicate the realities of climate change to the public and the policy makers? I don't have advice to give them really because all the circumstances are different. Except that we have to go on portraying the truth. And that's what science has done ever since Galileo. I mean for 500 years, that's what scientists do. The scientists don't take a notice of fashion and don't take notice of political influence and don't take notice of any other kind of influence. The only influence that they should take notice of are the evidence which they find and which their discipline teaches them to assess. You must get a lot of feedback from people who watch your shows. How do you respond to people who don't accept the science of climate change? It's very difficult. If they won't take notice, if they won't believe the figures, what can you say? It seems to be an extraordinarily offensive thing to do. To say to a scientist, your figures are wrong. Of course there are complex statistics and simple statistics and we know that statisticians and the science of statistics is a sophisticated one and then figures don't automatically yield up the truth. But you can only be honest and you can only work to the facts as you see them and as your discipline teaches you to deduce them.