There were so many strange surprises, and many times we were busy just trying to understand what was going on. The mechanism we seemed to be finding was very different from any theoretical ideas about how it should work. It seemed to be much more effective than we had ever imagined. It seems as if an electron is able to help form a small particle—a molecular cluster, as we call it—and then the electron can jump off and help another one. So it’s like a catalytic process. It was a big surprise that it is so effective.
These types of experiments had not really been done before, and we had to find new techniques in order to do them. Once we had the results, it was necessary to understand completely what was going on. So it was a very intense period of work, almost hypnotic.
Now there are other experiments, like the CLOUD project, also designed to investigate the effects of cosmic rays. How will this build on your work?
CLOUD is an international collaboration [sponsored by the European Organization for Nuclear Research, or CERN] that is taking place in Geneva, but it’s going to take a while before any results come out of that. It was approved last year, and building the machine will take at least three years. That’s a problem with science: You have to have a lot of patience because results are very slow to come.
If the scientists at CLOUD are able to prove that cosmic rays can change Earth’s cloud cover, would that force climate scientists to reevaluate their ideas about global warming?
Definitely, because in the standard view of climate change, you think of clouds as a result of the climate that you have. Our idea reverses that, turns things completely upside down, saying that the climate is a result of how the clouds are.
How do you see your work fitting into the grand debates about the causes of global warming and the considerations of what ought to be done about it?
I think—no, I believe—that the sun has had an influence in the past and is changing climate at the present, and it most certainly will do so in the future. We live in a unique time in history, because this period has the highest solar activity we have had in 1,000 years, and maybe even in 8,000 years. And we know that changes in solar activity have made significant changes in climate. For instance, we had the little ice age about 300 years ago. You had very few sunspots [markings on the face of the sun that indicate heightened solar activity] between 1650 and 1715, and for example, in Sweden in 1696, it caused the harvest to go wrong. People were starving—100,000 people died—and it was very desperate times, all coinciding with this very low solar activity. The last time we had high solar activity was during the medieval warming, which was when all of the cathedrals were built in Europe. And if you go 1,000 years back, you also had high solar activity, and that was when Rome was at its height. So I think there’s good evidence that these are significant changes that are happening naturally. If we are talking about the next century, there might be a human effect on climate change on top of that, but the natural effect from solar effect will be important. This should be recognized in the models and calculations that are being used to make predictions.
Why is there such resistance to doing that? Is the science that conflicted or confusing? Or is politics intervening?
I think it’s the latter, and I think it’s both. And I think there’s a fear that it will turn out, or that it would be suggested, that the man-made contribution is smaller than what you would expect if you look at CO2 alone.
Have you had a hard time getting funding?
For an eternity, I would say. But there are no oil companies funding my work, not at all. It sounds funny, but the Danish Carlsberg Foundation—you know, the one who makes beer—they have been of real support to me. They have a big foundation; in Denmark it’s one of the biggest resources for science. It’s because the founder of Carlsberg wanted to use scientific methods to make the best beer. It’s probably the best beer in the world, because of science.
If cosmic radiation is in fact the principal cause of global warming, is that good or bad news for human beings?
That’s a good question because you would have to say that we cannot predict the sun. And, of course, that would mean that we couldn’t do anything about it.