Published online 5 September 2008 | Nature | doi:10.1038/news.2008.1086

News: Q&A

American climate scientist James Hansen explains why he's testifying against coal.

James Hansen: no friend of coal. AP

James Hansen, the director of NASA's Goddard Institute for Space Studies in New York City, is well known for rattling his nation's political establishment. This week, the climate scientist was in London, UK, to testify on behalf of activists who defaced a coal-fired power station in Kent. Geoff Brumfiel caught up with Hansen at a London hotel to find out what has got him all hot and bothered.

Why did you come to testify?

Nothing could be more central to the problem we face with global climate change. If you look at the size of the oil, gas and coal reservoirs you'll see that the oil and gas have enough CO 2 to bring us up to a dangerous level of greenhouse gases in the atmosphere.

There's a potential to solve that problem if we phase out coal. If we were to have a moratorium on coal-fired power plants within the next few years, and then phase out the existing ones between 2010 and 2030, then CO 2 would peak at something between 400 and 425 parts per million. That leaves a difficult problem, but one that you can solve.

Do you think that leaders like UK Prime Minister Gordon Brown have lived up to their promises on climate change?

It depends on whether they will have a moratorium on coal-fired power. I think that the greenest leaders, like German chancellor Angela Merkel and Prime Minister Brown, are saying the right words. But if you look at their actions, emissions are continuing to increase. All of these countries and the United States are planning to build more coal-fired power plants. And if you build more coal-fired power plants, then it is not possible to achieve the goals that they say they are committed to. It's a really simple argument and yet they won't face up to it.

So do you think that these activists were justified in doing what they did?

The activists drawing attention to the issue seems to me as justified. You should try to do things through the democratic process, but we really are getting to an emergency situation. We can't continue to build more coal-fired power plants that do not capture CO 2 if we hope to solve the problem.

We need to get energy from somewhere. So if we're not getting it from coal, then where?

The first thing we should do is focus on energy efficiency. The fact that utilities make more money by selling more energy is a big problem. We have to change those rules. Then there is renewable energy — in order to be able to fully exploit renewable energy, we need better electric grids. So those should be the first things, but I think that we also need to look at next-generation nuclear power.

Some have said you are hypocritical for flying all the way from the US to the UK just to testify. How do you respond?

I like to travel as little as possible, not only because it uses less CO 2 but because I prefer to do science. But sometimes there are things which are sufficiently important that I think it makes sense.

What do you think the roll of the scientist should be in the broader societal debate on climate change?

I think it would be irresponsible not to speak out. There is a clear gap between what is understood by the relevant scientific community and what is known by the public, and we have to try and close that gap. If we don't do something in the very near future, we're going to create a situation for our children and grandchildren that is out of control.