Science - April 10, 2014

Rik Leemans: scenarios for uncertainty


He is a bridge-builder: someone who brings different disciplines together. So it is ironic that Rik Leemans finds himself in the academic field that has polarized opinion more than any other topic since the shape of the earth: climate science. Himself a highly driven scientist, he has an equally resolute faith in the individual: ‘That is probably where the change will come from.’

At the kitchen table in his Bennekom home, professor of Environmental Systems Ana­lysis Rik Leemans opens up a laptop to show a PowerPoint he used in a lecture this afternoon. One slide shows the increase in CO2 emissions predicted in scenarios made 10 to 20 years ago. Leemans: ‘What is striking is that the scientists have consistently been over-cautious. If, for example, you take the most extreme scenario made in 1992 for CO2 emissions in 2015, you can see that the reality is going to be way beyond it. Twenty years ago we were mainly talking about future, hypothetical increases in CO2 emissions and climate change, but nowadays we can observe the changes as they happen. We can now test old scenarios.’
And yet accusations of doomsday scenarios, pessimism and alarmism continue to fly. ‘Is the IPCC exaggerating the effects of climate change?’ asked the Dutch daily
de Volkskrant as soon as the last report by the UN climate panel was published earlier this month. The report contained a series of worrying scenarios. If CO2 emissions continue at the current rate, world temperatures will have risen by an average of 4 to 5 degrees by around 2100. Many ecosystems and farming regions cannot adapt to this, oceans will acidify and coastal regions will be threatened by rising sea levels. Leemans worked on the report as a review editor, supervising the soundness of the content and integrating commentary by dozens of scientists. 
Climate scientists have become cautious as a result of the public debates, says Leemans. Not even the insight that old scenarios were too conservative will change that. ‘It is very difficult to present extreme scenarios to the public because you are dismissed as a prophet of doom. Sceptics and climate change deniers often attack you personally too, so scientists err too far on the side of caution in order to pre-empt criticism. It is sometimes called erring on the side of least drama.’

This tendency to underestimate means that the reality consistently changes faster than the scenarios predict. ‘For example, our estimates of the growth of energy consumption in China were far too low. Ten years ago the average Chinese person used as much energy as our fridges. Now the average consumption among the Chinese is around the world average, but since you are talking about one billion people, that soon adds up.’

Great education

No one could have predicted that Leemans’ work would revolved largely around modelling global processes. ‘My father was a vet. I often went along with him to look at the big animals – cows and pigs on farms. I loved nature, but my father did have a very commercial approach to animals. At some point I consciously chose a different discipline to my father’s. I went to Nijmegen to do a degree in Biology, precisely in order to be able to study ecology and the whole picture, and to work with plants.’ One of his teachers was botanist Victor Westhoff. ‘I studied geobotany, aquatic ecology and environmental studies. I really had a great education.’
In the course of his PhD research at Uppsala in Sweden, he met paleo-ecologist Colin Prentice. ‘Colin looked at developments in vegetation from the perspective of ice ages and over periods of thousands of years. And he modelled everything. Under his supervision I developed a model for the growth and dynamics of tree species in old-growth forest.’
Leemans would later go on to expand his model to include all coniferous forests in northern regions, and later to become a global vegetation model. ‘Modelling vegetation was the start of an entirely new subject area. The model describes the climate and vegetation zones of the world. Where does tundra give way to coniferous forest, where does coniferous forest give way to deciduous forest, and where, in drier zones, does forest give way to grasslands or desert?’

He ended up at the Dutch National Institute for Public Health and the Environment, the RIVM, where he made an international name for himself by developing scenarios for climate change and the effects of economic developments and population growth on land use. ‘Everywhere I looked I saw trees being felled, intensive farming and cultural landscapes. There is very little natural vegetation left.’

Building bridges

Stimulating cooperation between disciplines and between individual researchers in his group is a recurring theme in Leemans’ work. This is because the creation of models and scenarios requires input from various different disciplines, such as ecology, economics, social sciences, agricultural research and information technology.
Different disciplines speak different academic lan­guages and see things in different ways. ‘At some point I got strong criticism of my model from the economists. In that situation you could say you don’t want anything more to do with economics. I prefer to say: fine, come on board then, and build economic insights into the model. So not to go on the defensive, but invite your critics in. In which case you need to be able to ask the right questions and to be a good listener, so as to understand what others mean. The concept of value, for example, has one meaning to an economist and quite another to an ecologist.’
Leemans has used these social skills in setting up various international research initiatives in the field of global change, as well. ‘If you work on an interdisciplinary basis, you have to be open to building bridges. I don’t know if I am particularly good at that, but it is how I do it. Going on talking and generating ideas until you come up with a solution to the questions you want to answer between you. Looking for those creative solutions in group collaboration is one of my strengths, I think. One advantage I have is that models are quantitative, mathe­matical descriptions of reality, with no specific worldview behind them.  That makes collaboration easier.’

Interdisciplinarity has a big advantage, Leemans notes. Publications which relates to several different disciplines are cited more often and have much more impact. This is true of the journal Current Opinion in Environmental Sustainability, which Leemans launched six years ago. ‘There were a lot of books and reports coming out on climate change and global change, but they don’t reach many people. We ask the best authors to write a review on a particular theme. That formula has gone down very well.’

Solar panels on the roof

All the scenarios show that if CO2 emissions continue at their current rate, it is going to be difficult to curb the rise in global temperatures. Even limiting the rise to a maximum of two degrees will be a huge challenge. You can compare it to a bucket that is full, says Leemans. Before we reach the temperature limit of two degrees, we can put another 370 gigatons of CO2 into the atmosphere. Every year we eat into that quota at a rate of about 11 gigatons worldwide, so within 30 years it will be used up. ‘Even if we halve emissions quickly, it will take 70 years.’
‘So if we want to stay within an increase of two degrees, we need to cut emissions very drastically – by 80 or 90 percent. The longer you wait, the harder it gets, and the more drastic the measures you will have to take. But it can be done; it is not impossible, technically. We have to get away from coal, or start storing CO2 underground. We have to look at how to save energy, alternative fuels, wind and solar energy. That is why I’ve got 16 solar panels and a solar boiler on the roof. In March, 75 percent of our energy came from them. I live in a big house, but it has a timber frame. Because there is less stone and cement, it heats up faster. I do this partly out of idealism, but also to set a good example.’
Partly as a result of the economic crisis, climate change seems to have disappeared from the political agenda across the board. Five years ago, Leemans spent a day in the lower house of the Dutch parliament at the invitation of the parliamentary committee on the environment, in order to answer questions about IPCC reports.
‘Due to the balance in the lower house, with the conservative VVD and right-wing PVV, half of those invited were scientists, and the other half were climate sceptics. I thought it was a farce. I hope operational arguments are given more weight in policymaking than emotional arguments. But you also have to realize that policymakers and politicians have their worldviews just like you do. Liberals often espouse the idea that the earth is robust and that the consequences of climate change will resolve themselves.’ 

All things considered, is Leemans optimistic or pessimistic about the future? ‘I am pessimistic about heads of state and policymakers in most countries. There is a lot of conservatism and slowness. But if I look at cities, companies and individuals, I am much more optimistic. There things can suddenly start moving fast. Rotterdam wants to be climate-neutral, and San Francisco has got a long way towards it already. At the local level, there is a lot going on. That is probably where the big change will come from.’

Rik Leemans (1957)

1976  Degree in Biology, Radboud University Nijmegen
1989  Thesis: ‘Description and simulation of stand structure and dynamics in some Swedish forests’ Uppsala University, Sweden
1988 – 1990 Researcher at IASA, Austria
1990 – 2003 Senior researcher at RIVM, Bilthoven
2000 – 2003 Professor of Integrated Land-use Modelling, Wageningen UR
2003  Professor of Environmental Systems Analysis, Wageningen UR
2012  Professor of Earth System Science, WUR (acting until 2015)

‘A real networker’

‘I got to know Rik in 1994 when I did my final thesis at the RIVM. He was organizing a meeting which brought ecologists from all around the world together in one room. I was impressed by that. Rik is a real networker, he knows all the leading lights internationally, and from his many travels and vast knowledge of the literature, he has a broad view of the world. Busy as he is, he organizes the interaction and collaboration in our group between researchers working on very different topics. He also makes time for breaks and for lunchtime walks. That keeps the lines short.’

Arnold van Vliet, researcher in the Environmental Systems Analysis chair group


‘Rik came to the chair group just as I was finishing off my PhD research. I got to know him as an inspiring professor with a hands-on style of leadership. His door is always open for everybody and he actively helps think through both scientific questions and practical issues. It is extraordinary how he manages to lead two groups of more than 60 people, take part in international forums, and still have time to keep up with his subject and carry on publishing.’

Lars Hein, professor of Ecosystem services and environmental change in the Environmental System Analysis chair group

Re:actions 1

  • Allen M. Solomon

    Between eating reindeer pizza above the Arctic Circle in Sweden, and sipping wine in the heurigers near Vienna, my scientific research experiences with Rik has been one in which I always benefitted from his great imagination and his even greater energy. His respected professional reputation is well earned and well deserved. I do claim credit for part of that reputation; I taught him to brew good beer!