Surely the biggest problem we have in the world is that we all die. But we don't have a technology to solve that, right? So the point is not to prioritize problems; the point is to prioritize solutions to problems.

If every country committed to spending 0.05 per cent of GDP on researching non-carbon-emitting energy technologies, that would cost $25 billion a year, and it would do a lot more than massive carbon cuts to fight warming and save lives.

I think it's great that we have organisations like Greenpeace. In a pluralistic society, we want to have people who point out all the problems that the Earth could encounter. But we need to understand that they are not presenting a full and rounded view.

The fact that we're catching more fish per person than we've ever done before doesn't mean that there are not particular places where we've managed fisheries badly.

I think Al Gore has done a great service in making global warming cool. He's basically taken it from a nerdy, almost ignored issue to making it what it is - namely, a problem.

When thinking about the future, it is fashionable to be pessimistic. Yet the evidence unequivocally belies such pessimism. Over the past centuries, humanity's lot has improved dramatically - in the developed world, where it is rather obvious, but also in the developing world, where life expectancy has more than doubled in the past 100 years.

I'm a vegetarian, but I don't expect other people not to eat meat.