In the rich world, the environmental situation has improved dramatically. In the United States, the most important environmental indicator, particulate air pollution, has been cut by more than half since 1955, rivers and coastal waters have dramatically improved, and forests are increasing.

The second thing is, if you want to do something about global warming, you have to think much more long-term. There is something wrong with saying we should start using renewables now, while they are still incredibly expensive.

Think on a 50-year scale, which is a much more natural time-scale for global warming. The US is right now spending about 200 million dollars annually on research into renewable energy.

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.

To prepare adequately for the challenge of global warming, we must acknowledge both the good and the bad that it will bring. If our starting point is to prove that Armageddon is on its way, we will not consider all of the evidence, and will not identify the smartest policy choices.

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 really try to say things as they basically are and it so happens that it is a good message that things are getting better, but there are still problems.