German Climatologist on Criticism of IPCC

'We Received a Kick in the Pants'

German physicist Hans Joachim Schellnhuber is one of Angela Merkel's advisers on climate change. In an interview with SPIEGEL, he discusses extreme weather events, global warming's winners and losers, and the effects of the crisis of confidence in climate research.

SPIEGEL: Mr. Schellnhuber, Russia is burning and floods have inundated Pakistan. Are such extreme weather phenomena increasing because of gradual climate change?

Hans Joachim Schellnhuber: Such events certainly do correspond to what we expect from a warmer world. We have seen record average global temperatures for more than a year now, and that increases the likelihood of regional heat waves like the one in western Russia at the moment. Besides, our climate models show that the South Asian monsoon is becoming more temperamental as a result of anthropogenic changes to the environment.

SPIEGEL: There have also been forest fires and floods in the past. Isn't it too easy to automatically link natural disasters to climate change?

Schellnhuber: Of course it would be wrong, from a scientific perspective, to establish this relationship indiscriminately. But it would be just as unscientific to stop searching for such relationships, merely because the public's interest in climate change has temporarily diminished.

SPIEGEL: In Russia, in particular, fire prevention has failed. The forest service was abolished, and fire departments in many places are in terrible condition. Do these major fires show that extreme weather situations don't necessarily lead to catastrophes, but that poor crisis management is really to blame?

Schellnhuber: That's undoubtedly correct. In most cases, it's social mismanagement that creates the conditions for social catastrophes. Often one can get away with having inadequate precautionary measures, provided the weather plays along. But extreme weather relentlessly exposes human mistakes and our crimes against nature. The German state of Brandenburg (editor's note: where the Potsdam Institute for Climate Impact Research is based) offers an example of the right way to do things. Even though there are more forest fires here than in the past, due to global warming, the surface area burned by the fires has decreased substantially, thanks to improved monitoring with smoke detectors.

SPIEGEL: As climate adviser to the chancellor, you have a particularly high profile. Because of your frequently ominous predictions, critics have dubbed you the "Cassandra of Potsdam," after the figure in Greek mythology whose predictions always went unheard. Why do you always have to scare people?

Schellnhuber: Let me answer your provocative question in an objective way. As an expert, it's possible that I tend to point to dangers and risks more than to opportunities and possibilities -- similarly to an engineer who builds a bridge and has to make people aware of everything that could cause it to collapse. Warning against a possible accident is in fact intended to reduce the likelihood of an accident. And a sudden shift in the climate could have truly catastrophic consequences. Besides, in Greek mythology Cassandra was always right -- unfortunately.

SPIEGEL: Does that justify constantly predicting the end of the world?

Schellnhuber: Naturally, we have to be careful not to dramatize things. After all, scientific credibility is our unique selling point. But I do confess that when you have the feeling that people just aren't listening, it becomes very tempting to turn up the volume. Naturally, we have to resist this temptation. On the other hand, the media often portray my statements in one-sided ways…

SPIEGEL: Can you give us an example?

Schellnhuber: Take agriculture, for example. If temperatures rise, harvests will suffer, in cereal crops, for example. But at the same time the higher level of CO2 in the atmosphere will lead to improved fertilization of plants. This fertilization from the air will make up for a large portion of the heat damage, perhaps even overcompensating for it. In other words, we could even get higher yields for a certain amount of time, provided there is enough water. In talks I give on the subject, I always mention both effects: the heat damage and the CO2 fertilization. But such subtleties are lost when it comes to how the issue is perceived by the general public.

SPIEGEL: It wasn't just misunderstandings that shook public confidence in climate research in recent months. A number of statements in a report by the Intergovernmental Panel on Climate Change (IPCC), such as one on the supposedly rapid melting of the Himalayan glaciers, turned out to be appalling errors.

Schellnhuber: There were only a few slip-ups, but they were extremely vexing. The IPCC is in the public eye, and there is so much at stake that we cannot allow mistakes of this magnitude to be made. The IPCC now needs to do its homework to overcome the credibility crisis that's occurred. We received a kick in the pants that probably did us a lot of good.

SPIEGEL: A scientific investigation panel in the Dutch parliament accuses the IPCC of overemphasizing the negative consequences of climate change.

Schellnhuber: On balance, this accusation is unjustified. It's not like the IPCC is hiding its true face, which is characterized by ugly exaggerations, behind a mask. For example, the IPCC has deliberately made cautious and restrained predictions regarding the rise in sea levels. The IPCC is set up in such a way that it smoothes things out as much as possible and uses conservative wording, so that all scientists involved can ultimately support the report.

SPIEGEL: Anyone who soberly asks for a cost-benefit analysis of climate change is demonized as a heretic. Why is it such a taboo to talk about the advantages of global warming?

Schellnhuber: You're right -- we do have to highlight the opportunities and benefits for some regions of the world more than we have done so far. There will certainly be winners, at least temporarily, especially in the northern latitudes. At a conference in Moscow, Russian Prime Minister Vladimir Putin told me quite openly: We are looking forward to global warming. We won't need to heat as much, our fleet will be able to operate in an ice-free sea, and we'll have more fertile land to farm. But is this really true? The current forest and peat fires show that global warming could also have drawbacks for Russia. The problem is that the consequences of climate change, both good and bad, have not been adequately studied yet. More than 90 percent of funding is still being used to investigate scientifically if humans are responsible for climate change. But this question has already been answered a long time ago: They are.

Part 2: 'We Are Very Much in the Dark'

SPIEGEL: Is Germany more likely to be among the winners or the losers?

Schellnhuber: It's hard to say. We are currently working on a comprehensive study of this issue in Potsdam. Unfortunately, there are still many unknowns. Climate impact research still lags behind the rest of climate research by about a decade. The following example illustrates how complex all of this is: On the surface, warmer temperatures are fantastic for tourism along the North Sea and the Baltic Sea. On the other hand, the beaches there will first have to survive the rise in sea levels. And that's not a trivial matter. In Hawaii, one-third of beaches are already threatened by flooding. So do the advantages outweigh the drawbacks? We don't know yet.

SPIEGEL: Apparently it's just as hard to predict whether there will be more and stronger hurricanes in the future.

Schellnhuber: It's true that it is still unclear whether they will increase in frequency. A few studies do note that wind speeds in tropical storms could increase. But given that climate research is still in its adolescent phase, the next study could reach precisely the opposite conclusion.

SPIEGEL: The computer models come to more obvious conclusions with regard to storms in our moderate latitudes. Outside the tropics, hardly anything will change. Germany, according to the models, will see neither more nor more powerful storms, although the storm paths of low-pressure zones are likely to shift.

Schellnhuber: Yes, I know that my colleagues at the Max Planck Institute for Meteorology (MPI-M) in Hamburg gave the all-clear signal after doing their simulation. But this is a preliminary result at best. Personally, I don't believe that there will be no changes in storms in a world that's, say, five degrees Celsius warmer. That would greatly surprise me, given that it's such a non-linear phenomenon.

SPIEGEL: But the public has gained the impression that superstorms with previously unheard of destructive power will devastate our cities in the future. Shouldn't climatologists at least make it clear that they are still largely in the dark?

Schellnhuber: The simple answer is yes. In fact, we are very much in the dark on this issue. On the other hand, that fact is by no means reassuring. Do we really want to embark on a planetary experiment with an unknown outcome? Do we want to simply allow climate change to happen and then calmly observe the storms to see whether or not they're actually getting worse?

SPIEGEL: Was it generally a mistake not to have done more to point out the serious gaps that still exist in climate research?

Schellnhuber: Once again, all I can say is that we shouldn't adopt a bunker mentality, especially in climatology. Instead, all the doubts should be clearly and candidly addressed at conferences, even when it's painful. Just think how passionately Heisenberg, Bohr and Einstein used to argue about the fundamental aspects of quantum theory. But that was a small, manageable group of physicists who respected each other and constantly met in person…

SPIEGEL: …and global politics wasn't an issue.

Schellnhuber: Exactly! In climatology, it would be difficult, even just from a technical point of view, to conduct the entire scientific debate in full public view. That's because politicians and society want the clearest, most unambiguous answers possible. And if we can't provide those answers, many people simply stop listening to us. They're basically saying: Don't bother us with your models and counter-models. Get back to us when you have all the answers.

SPIEGEL: Is that also the reason why there are some exaggerations in the summary of the IPCC report for political decision-makers?

Schellnhuber: They're not exaggerations, but a condensing of information. We scientists can't exactly slam tens of thousands of pages of scientific articles onto the table in front of parliaments and governments. Of course the results are condensed, but that doesn't mean they're not true. However, in the interest of scientific accuracy, perhaps we could abandon the overarching goal of the IPCC report, which is to deliver summary answers to all questions about the climate -- and sometimes just say nothing.

SPIEGEL: Isn't there also a risk that studies could be suppressed if they were likely to give a boost to skeptics of anthropogenic climate change?

Schellnhuber: Believe it or not, I don't practice self-censorship, and as a physicist, I'm accustomed to recognizing that new studies might correct my point of view, even if this translates into intellectual defeat. I wouldn't hesitate to tell the chancellor that there is a new study that suggests we are all backing the wrong horse and that humans are not to blame for climate change. Or perhaps we'll discover in 20 years' time that we can easily master a five-degree increase in global temperatures. I would be very happy about that. But from today's perspective there is no reason for such optimism.

SPIEGEL: You are fighting to limit global warming to two degrees Celsius. But it's already almost one degree warmer today than it was at the beginning of industrialization. Because of the greenhouse gases already circulating in the atmosphere, another increase in temperature by 0.6 degrees can no longer be avoided. And more than 30 gigatons of CO2 are still being emitted into the air every year. Isn't the two-degree target completely unrealistic?

Schellnhuber: Technically speaking it's probably still just about possible. But in 10 years' time it'll probably be too late. After that, it could be that the only solution will be global carbon management, that is, the artificial removal of CO2 from the atmosphere, perhaps through reforestation of degraded areas of land or the direct filtration and permanent disposal of carbon dioxide. That's the ace up our sleeve, which we would then have to play. Incidentally, I'm convinced that in the long term we should take the atmosphere back to the cooler state that prevailed in the Neolithic Age, when humans became sedentary.

SPIEGEL: What do you mean? It seems hubristic to assume we can simply program average temperatures on the planet, as if we were dealing with an air-conditioning system. Do you really believe that human civilization will collapse if the temperature rises by more than two degrees Celsius?

Schellnhuber: First of all, what's hubristic here is the way we are unscrupulously interfering with creation by burning all the fossil fuels. And of course the world won't end if temperatures go up by 2.01 degrees, let alone end suddenly. From today's scientific perspective, we could possibly live with a warming of two to three degrees. But that range should be the extent of it, because greater increases in temperature would trigger uncontrollable processes, leading to sudden and irreversible changes in ice sheets and continental ecosystems. The overwhelming majority of climatologists assume that a global temperature rise of four degrees would be an immensely dangerous route that we should avoid at all costs.

SPIEGEL: Why then have you, as one of the creators of the two-degree target, imposed such a magical limit to which all countries must slavishly adhere?

Schellnhuber: Politicians like to have clear targets, and a simple number is easier to handle than a complex temperature range. Besides, it was important to introduce a quantitative orientation in the first place, which the 1992 Framework Convention on Climate Change managed to elegantly wangle its way out of. And let's be honest: Even if we aim for the two-degree target, we'll end up somewhat higher. Whenever there's a speed limit, most drivers tend to go a little faster.

SPIEGEL: At the climate summit in Copenhagen, the prevailing impression was that the most important countries don't want any fixed rules at all.

Schellnhuber: It's true that the big picture remains unclear. For the time being, there will certainly be no substantial treaty among all 194 signatories to the convention. That's why we have to pin our hopes on smaller alliances for now, such as between the European Union and Brazil. What's happening in Brazil is unbelievable. In 20 or 30 years, they could meet all of their energy needs from renewable resources. Perhaps we'll all be driving with sustainable biofuel from Brazil soon. And such bilateral projects will certainly help set the unwieldy behemoth that is the global climate treaty into motion.

SPIEGEL: Which countries do you believe are best suited to bringing about a total rebuilding of industrial society?

Schellnhuber: Ultimately only democratic societies will be able to master this challenge, notwithstanding their torturous decision-marking processes. But to get there perhaps we'll need innovative refinement of our democratic institutions. I could imagine assigning 10 percent of all seats in parliament to ombudsmen who represent only the interests of future generations.

SPIEGEL: Mr. Schellnhuber, thank you for this interview.

Interview conducted by Olaf Stampf and Gerald Traufetter


Physicist Hans Joachim Schellnhuber, 60, is a world famous physicist and climate researcher. After working in Germany and California, he was appointed founding director of the Potsdam Institute for Climate Impact Research (PIK) in 1991, which he still leads today. He is an adviser to German Chancellor Angela Merkel on climate-related issues as chair of the German Advisory Council on Global Change (WBGU).