“Bernese climate research is an international brand”

Thomas Stocker is one of the flagship figures of the University of Bern and a climate researcher with an international reputation. Among other things, he held a leading position in the Intergovernmental Panel on Climate Change (IPCC). He is now retiring. In this interview, he looks back on his career, talks about an offer from Cambridge and discusses orchids and road bikes.

Interview: Kaspar Meuli

Read the original uniAKTUELL article here (in German).

Thomas Stocker, you studied physics at ETH Zurich. How did you become a climate researcher?

I started with physics, although I was interested in many other things too. Then, in 1980, as a student, I had the opportunity to work for two months at the Institute for Snow and Avalanche Research on the Weissfluhjoch, where I carried out simulations of snowpack stability. During that time, I realised that I was fascinated by the Earth system. By chance, I heard about a new degree programme at ETH called environmental physics, which I then completed. My diploma and my doctorate were extremely interesting, but extremely theoretical: they dealt with wave motions in rotating channels and lakes. After a short postdoc in London, again in this field, the subject became a little too narrow for me; I wanted to broaden my horizons. Then the opportunity arose to go to McGill University in Montreal, where a climate research group was being set up at exactly that time.

Did you already know then that you wanted to devote yourself to this field of research?

Climate research fascinated me from the very beginning, but just like today, back then you moved from one postdoc to the next and didn’t know whether you had a longer-term future in research. That is why, during my doctorate at ETH, I had obtained a teaching qualification in physics for upper secondary schools, so I had a plan B – which I never had to activate.

Then, at the first ProClim conference in Locarno in 1990, I met a prominent researcher from the USA, Wally Broecker. We got talking and he asked me whether I would like to join him at Columbia University’s Lamont-Doherty Earth Observatory near New York. At the time, it was the world’s number one place for palaeoclimate research, i.e. the reconstruction of the climate of earlier times – a fantastic offer. And at that time Broecker was putting forward the interesting hypotheses that ocean circulation can change rapidly and that this was the reason for the abrupt temperature jumps in climate history that had been found in the Greenland ice cores. Broecker later called these changes Dansgaard-Oeschger events.

And did it work out with New York?

I was thrilled and thought I now had my next position. Then, after a few months, Wally Broecker got back in touch and explained that I first had to write a research project proposal for the US Department of Energy. In the end, the project was approved and my salary was secured. I would have liked to stay in New York for four years, but after two years the call came from Bern …

You were encouraged to apply for a professorship?

Yes. A year earlier, Hans Oeschger had already sent me the advertisement for his successor and drawn my attention to the position. But I hadn’t applied, as I was just a young postdoc and wouldn’t have dreamt of applying for a position that, at the time – in 1992 – was the only professorship in Switzerland dealing with climate change. Climate change in the recent period, that is, the past 100,000 years and the future.

And so someone gave you a little nudge?

After the first round, the University of Bern’s search committee was back to square one, as its preferred candidate had declined. They then asked around in the community for interesting candidates, and I was very lucky that my boss at Lamont, Wally Broecker, thought I could continue my research in Bern and recommended me …

… and then, at the age of 34, you were actually appointed …

… yes, and when I arrived here in Bern, my knees were shaking and I wondered whether it would work out. All at once I was responsible for a division of the Physics Institute with 28 people, some of whom had many years of experience and had done international research. And now this youngster from America comes along and takes over as head. It only worked thanks to the fantastic colleagues I was able to work with here.

When you began to take an interest in climate research, nobody knew how important this field would become. Does your career also have to do with the fact that you were ready at the right time?

It is indeed true that climate research really picked up speed at the end of the 1980s. And the Climate and Environmental Physics division at the University of Bern, established by Hans Oeschger, was at the forefront – on the one hand with the understanding of the climate system through the analysis of ice cores, which enabled Hans Oeschger and his team to prove that the increase in greenhouse gases since industrialisation has been caused by humans and that concentrations during the Ice Age were considerably lower still. And on the other hand, the Intergovernmental Panel on Climate Change (IPCC) had been founded in 1988 with the mandate of producing a first scientific status report on past and possible future climate change for the 1992 Rio Earth Summit and of outlining options for action. The University of Bern played a leading role even in this first report.

And then came the great interest from politicians and the public. You have become, so to speak, the face of climate research in Switzerland …

… this role simply came my way. The requests came of their own accord, and I made myself available. Not like today, when you have to have a strong presence on social media to attract attention.

Did you actually enjoy your role as an explainer of climate change in the media?

Yes. I certainly never did a home story in the “Schweizer Illustrierte”, but it gave me great satisfaction not only to work out robust statements by consensus in the IPCC, but also to communicate them to the outside world. The task of science is not only to generate knowledge but also to share it, especially on a topic of such relevance to society.

Climate research has long since become highly political. How far did you stick your neck out?

During my time at the IPCC, I didn’t stick my neck out at all, as I didn’t want to influence the assessment process.

But you have recently. You didn’t hold back in your criticism of the SVP, for example. You were very outspoken there.

Of course. I think, with my experience, you have to be. I don’t mince my words when there are such blatant attempts to exert influence ahead of votes. If a party tries to influence public opinion through manipulation and propaganda, I speak up.

You are now retiring, so you will no longer represent the University of Bern in public. Will you mince your words even less?

No. What matters is that my statements continue to be based on scientific facts. That has always been my aim: to address things pointedly and understandably, but also to provide well-founded information at all times.

So you won’t become a second Jacques Dubochet, the University of Lausanne’s Nobel laureate in chemistry who sympathises with the climate activists?

I think what he does is great. I may not be as much in the limelight as he is, but a few years ago, for example, I was very involved with the climate youth movement in the canton of Glarus, which actually led to the Green Party candidate being elected to the Council of States in a hotly contested election and to the Landsgemeinde adopting tangible climate protection, namely a ban on oil heating.

What was actually the greatest success of your scientific career?

What matters most to me is that the Climate and Environmental Physics division is in incredibly good shape today and is a strong international brand on the map. But that is not my achievement; it is that of all the staff who have done research with us over the past 30 years and have worked with great commitment for research and teaching.

Let me ask about your personal highlights in a slightly different way: which of your more than 260 papers has been cited most often?

Probably the publications on the reconstruction of CO2 and CH4 concentrations over the past 800,000 years using ice cores, which we were able to carry out as part of the European project EPICA. This world record still stands today. Our second successful field is modelling the climate system with so-called models of reduced complexity. With these simplified climate models, which are indispensable for understanding our measurements on polar ice cores, we can run simulations and test hypotheses extremely efficiently. Despite the simplicity of these models, we can still hold our own internationally.

When people retire, they are often asked about their hobbies: I have heard that you ride a road bike and breed orchids. Is that true?

I have never bred orchids. But yes, I have always been interested in native orchids – that’s a bug my biology teacher at grammar school gave me. Over the years I collected literature on these flowers and also looked out for orchids in nature on hikes. There are over 40 native orchid species in Switzerland – all of them endangered. I also went through a phase of collecting old botanical illustrations from the 18th century – that fascinated me at the time, but it has since subsided somewhat. Somehow I can get quite enthusiastic about new things and then get to the bottom of them.

And the road cycling?

I started that during the pandemic. On the urgent advice of my two daughters, I fortunately bought a road bike right at the beginning, before the delivery problems started. Since then I have been out and about in the area around Bern – last Saturday, for example, with one of my daughters in the Schwarzenburgerland. We covered 70 kilometres and 1,300 metres of elevation gain. It was great.

Alongside all the successes, you have also experienced defeats. In 2015, you would have liked to be elected Chair of the IPCC, but you lost. Did that hurt a lot?

Yes, it did bother me, but not for very long. And looking back, I have to say: this defeat was the best thing that could have happened to me. In this global election campaign, I learned that above the office I was able to hold as Co-Chair of the IPCC Working Group “The Physical Science Basis”, which was very scientific in nature, things become extremely political. You are exposed to completely different forces there.

You were probably already aware that this office was no longer just about science when you stood for election …

Yes, I knew that, but I wasn’t aware that in this sphere it is no longer about science at all. That was probably a little naive.

You were a flagship figure of science for decades. Did no one ever try to poach you? Did a headhunter never turn up in your office with an irresistible offer?

There were several enquiries. One of them was to take up a professorship at the University of Cambridge. Your spontaneous reaction is: great, that needs to be looked at more closely. The idea was to set up an interdisciplinary climate research centre, like the one we have at the University of Bern with the Oeschger Centre. When I then asked what budget would be available for this, I was told: 10,000 pounds a year. I burst out laughing and said that in my division I would use that sum to organise a seminar for two semesters. That was the end of the enquiry.

You have two daughters. Did you advise them to pursue a scientific career?

No, what I passed on to Anna and Francesca is an enthusiasm for nature and the natural sciences. The elder studied physics at the University of Bern and the younger studied biochemistry here too. Now one works in the federal administration and the other in the pharmaceutical industry, and both are happy with their paths.

What would you study today if you were 20 again?

The same again, no question. Environmental physics.