You started life as a statistician. What sparked your interest in the environment?
I found university a little dispiriting. I thought I would enter the great halls of Plato, but instead I entered the halls of an intellectual sausage factory. I wanted to do something not on the main course, and chose the environment.
What is your position on global warming?
Global warming is real - it is man-made and it is an important problem. But it is not the end of the world.
You have been branded a climate-change denier. Have you changed your mind?
No, I haven't changed my mind, but the global warming debate is so polarised that there is space for only two possible viewpoints: either it's the end of the world, or you think it is the greatest hoax ever perpetrated. Because I dared to be sceptical, a lot of people pushed me into the deniers' camp.
Are you still sceptical?
I have been sceptical all along, but about the solution. Our current solution - the Kyoto approach - doesn't work.
What's not working?
The UN summits are PR vehicles for politicians so they can all get together and look like they're doing something.
What's your view of the UN Intergovernmental Panel on Climate Change?
I would say 90 per cent of what the panel tells us is right, which is pretty good for a very complex subject. But the UN-led policy solutions are incredibly poor.
So what's your solution?
We need to invest dramatically in green energy, making solar panels so cheap that everybody wants them. Nobody wanted to buy a computer in 1950, but once they got cheap, everyone bought them.
How did it feel when critics accused you of being scientifically dishonest in your book The Sceptical Environmentalist?
I always felt, when people were attacking me, that they were attacking the idea. When the dishonesty decision got reviewed by the Danish ministry of science, they found that it was factually vacuous, so it was overturned.
Do you enjoy provoking controversy?
No. A lot of people think I do, but I would love the day when we don't need my voice in the debate any more.
What was your view of the Climategate scandal at the University of East Anglia?
There was poor intent and bad will involved on the part of the researchers, but I also think it was vastly overplayed.
Do you think it had a damaging effect? Fewer people now believe in climate change.
Climategate was only a touch point for that; it is not the main reason. We have been scared silly for a number of years and eventually you tire of being scared silly.
Do you blame the activists for that?
It's not just activists; there's Al Gore, for example. We shouldn't base policy decisions on fear.
Are you involved in politics?
No. I have great respect for politicians; they do a difficult and often thankless job. But I'm not politically active.
Do you believe David Cameron will deliver the "greenest government ever"?
I'm not surprised that's a quotation from him, but that doesn't seem to be where they're putting their money. In Britain, I see an incredible split between stating what you'd like to see and making the policies for that to happen.
Do you have religious faith of any kind?
I tentatively believe in a God. I was brought up in a fairly religious home. I think the world is compatible with reincarnation, karma, all that stuff. But fundamentally, you have to do good in this life towards your fellow man, so I guess I'm a humanist with the potential of [believing in] a God.
You've said that being openly gay is a civic responsibility. What do you mean?
When I grew up, I didn't see many likeable role models. You could either be a ballet dancer or someone extreme whom people would snigger at. I'd like to show the next generation that you can be regular, ordinary and successful.
How has your sexuality affected your career?
I didn't want to be the gay guy who talks about the environment. I wanted to be the guy who talks about the environment who happens to be gay. I think that has turned out pretty well.
Is there a plan?
In the larger scheme, no. There have been meso plans, but not meta plans.
Are we all doomed?
No. If you look across the centuries, we have created problems, but we've solved more. Our ingenuity seems to be an unlimited resource.
1965 Born on 6 January
1994 Receives PhD from the University of Copenhagen
1998 Publishes his first articles on the environment, causing media furore
2001 Publishes his book The Sceptical Environmentalist
2003 Cleared of "scientific dishonesty"
2004 Launches Copenhagen Consensus
2010 Calls for $100bn to be invested each year to fight climate change