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Scientific Ambassador Prof. Hans Joachim Schellnhuber

Hans Joachim Schellnhuber was the Director of the Potsdam Institute for Climate Impact Research (abbreviated PIK) until September 2018. He held this position ever since he had founded the institute in 1992.


Audio Version

Prof. Hans Joachim Schellnhuber interviewed by Thomas Prinzler | rbb Inforadio

Prof. Schellnhuber, as a systems researcher you observe the earth, the climate system as a whole. You repeatedly point out so-called tipping points; those are the moments in the course of climate change when something might drastically change. Are these points of no return? Will we be unable to do anything once we have reached them?

Well, it's not as simple as that. Our very complex environmental system allows for mainly two types of reactions.

First of all, there are those that we call linear. They are similar to, you might say, a continuous switch, which means that we move it, and thereupon at least one part of the system reacts. And when we return the switch to its original position, the system eagerly obeys and returns to its original state as well.

But tilting elements are very different from the mentioned case. If you put such a system under pressure, at a certain critical point all it needs is a minor additional change, a tap, and it tilts. After that you can't bring the system back with a similarly light tap. Maybe it is best to picture it this way: Imagine a heavy beam being in balance; then you tap the beam with your finger and thereby you make it tilt downwards on the right side into a stable position; if you try to bring it back to its original position with a similar force – a light tap with the finger – gravity will prevent you from bringing it back to its original position. Something similar happens when, for example, the Greenland ice sheet begins to melt almost unstoppably. However, self-reinforcing processes also come into play in this case. These ice sheets are at some points thousands of metres thick, so their surfaces are relatively high up and the temperature is lower at high altitudes. If something melts away, the surface sinks to lower altitudes that are warmer, which in turn further intensifies the melting.

Due to such processes and their associated risks, a “crash barrier” at a maximum temperature increase of two degrees has been created. This is a political target, but it has a scientific background, because we will probably avoid the important tipping points of the climate system if the temperature increase stays below two degrees. But if we exceed the two degrees, we will reach a considerably larger number of tipping points. Science is now trying to show more clearly that many such tilting processes will occur if we exceed these two degrees. And the overall picture does not look particularly promising.

Why don’t you grant us a glimpse at this not very promising picture? What are the tipping points that we have to be made aware of?

I've talked about Greenland already. Unfortunately, according to a new study by our institute, a global temperature increase by only 1.6 degrees could trigger great melting processes. I have a second example for you. The PIK has demonstrated that a global temperature increase by only 1.5 degrees Celsius could destroy about 90 percent of all coral reefs due to a combination of these factors: sea warming, sea level rises and ocean water acidification. And there are the large glacier systems, which would certainly melt.

It's sort of like looking at the human body. In general, two degrees sounds like a very small change. However, two degrees in this case refer to the body temperature balance of the earth. If you increase it by two degrees, it's like increasing the human body temperature by two degrees. And this is a real fever. Five degrees more would mean death. Of course, I am not saying that the earth will be dead once the global temperatures have risen by five degrees. But it is likely to lead to a dramatic change. Our civilization is strongly interconnected and very vulnerable. In the early days of mankind, tribal groups could avoid changes by migrating to other places. Today, megacities worth billions are located along the coasts where sea levels are rising. And extreme weather events in ever closer succession could severely interfere with the global supply chains of our just-in-time production.

“The collection of evidence is complete. The perpetrator has been identified”, you said. And now? What is to be done? Do you have a master plan for saving the world?

I would say that reason is always a good yardstick. You can call it rational thinking or common sense. Whether reason prevails is an entirely different question. In essence, reason and imagination and creativity can achieve a whole lot. However, I don't believe in the one all-encompassing master plan that could provide the right instructions for all the nations to follow. Simply because we will not be able to communicate it internationally. In this respect, it is more likely that leading by example – as does Germany with its energy revolution – could become a truly effective way of making an impact.

You are one of the internationally most renowned climate researchers, a member of the Intergovernmental Panel on Climate Change (IPCC), an institution that received the Nobel Peace Prize. You have been managing the PIK for over 20 years. Have you never thought about leaving Telegrafenberg?

But I really was abroad for a while and I resided in the UK for four years (2001-2005) when I was setting up the Tyndall Centre for Climate Change Research. I currently hold a parallel professorship at the Santa Fe Institute in New Mexico, USA. But it's true; essentially I've stayed true to the Telegrafenberg. And why is that?

Let me give you some historical background. After the reunification of Germany, plans were drafted – quite hastily and not always in the best way possible – to completely restructure the scientific landscape in the east of Germany. In 1991, I was told that a new institute focusing on “climate impact research” might be created and perhaps located on Telegrafenberg in Potsdam. I then came here and I took a look at this magnificent location. It was a foggy day. I can still remember it very well. Lignite fumes and Trabant exhaust gases were still hanging in the air. And yet, from what I saw – no matter how run-down the buildings were – I immediately had the feeling that if I wanted to work for a long time in one place in Germany, it had to be Telegrafenberg! What greater privilege could there be than to work at a location where German research has reached an absolute world-class level and has maintained it for many decades?

Additionally, a unique ensemble has been created here on the mountain; it is even internationally an exceptional collection of researchers and research institutions that reflect upon the future of the earth. In the institute itself we now have over 300 employees, plus an additional 100 visiting scientists every year, and we cooperate with the other institutes on the mountain: the German Research Centre for Geosciences, the Leibniz Institute for Astrophysics Potsdam and the Alfred Wegener Institute.

Therefore, I would have to be offered a very attractive alternative in order to move to a different location. I have received several offers, but none was interesting enough to lure me away from here. And now I will most likely be able to spend the last 30 years of my research life here.

Mr. Schellnhuber, you are a scientific ambassador of the state of Brandenburg and you travel the world a lot. What do you have to say to the world about Brandenburg as a science and technology location?

The background here is one of a kind worldwide. Until 1989 Brandenburg lay like a ring, like a collar, around the divided Berlin. And now the state is reunited with Berlin – maybe not yet politically, but in cultural, civilisational terms it is. This entire region stands for something extraordinary. Now, of course, I could talk about the usual things, the density of research institutions and so on, but perhaps it is more important to say this:

Here, especially after the German reunification, the opportunity arose to do things that someone who is stuck in a successful routine would not do. Luckily, we are not yet stuck. Maybe sometimes things are done in a sub-optimal way, but there is the opportunity to make the best of a large potential, and this is truly something extraordinary. I think that Brandenburg is certainly a federal state that is very devoted to research and innovation also under Minister-President Matthias Platzeck. Brandenburg could make a great contribution to Germany's energy revolution, to the switch to a truly sustainable energy system. I once called it the "Brandenburg Innovation Laboratory".

What visions for the future do you have? Most of the scenarios that have been created go as far as 2100. Neither of us will live to witness that future. But will we humans be able to continue to live on the planet?

Yes, of course! I have a wish rather than a vision. But, as you may know, a wish often fathers an idea. But equally the idea could father a wish. I mean, if you wish for a certain future – because you believe it would be the "right" one – it will hardly come in the desired form. But perhaps the people themselves will contribute to bringing the desired future closer to the real one, provided that they don’t just let everything run its course.

I think that in a functioning democracy we have all the means – technical, economic and also institutional – to act and transform ourselves in a way that would make not just our own generation prosper, but that would benefit also the generations born after 2100. And truly this is the physicist in me talking, because when we speak, for example, about renewable energies or the use of resources, we have to carry out an analysis first. And all these analyses reveal this: Yes, it's relatively easy to achieve our goal. What is ultimately needed is the social commitment directed towards seizing our potential. Of course a physicist cannot predict whether this will be successful. But at least I know that it is possible.