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Marine algae: Defying climate change on a rollercoaster

10. September 2018 - 13:10

If we imagine the world in the year 2100, climate change may well have altered quite a few things in the sea.  That’s why, at the Center for Earth System Research and Sustainability (CEN), I’m investigating how algae will react in the long term to new and extreme conditions. A ten-degree rise in water temperature? Significantly more CO2 dissolved in the sea – making the water more acidic?  Many of today’s algae wouldn’t be able to tolerate this, and computer models predict that the population could decrease by a fifth in the long term – with far-reaching repercussions for the oceans and the atmosphere around the globe. 

But is the alga of today the same as the alga of tomorrow? Algae reproduce rapidly and their populations are enormous. A generation is replaced within one or two days – an advantage when it comes to mutation, which can lead to beneficial genetic adaptations.

We put a type of diatom known as Thalassiosira pseudonana in hundreds of mini aquariums at different temperatures. Their “comfort zone“ is 22 degrees Celsius, but we also kept them in water that was four degrees warmer, at 26 degrees. According to the IPCC climate report, the temperature will have risen by this much on average by 2100. And this is just a mean value; peak temperatures – like those in a heat wave – will be much higher, which is why we wanted to provoke the algae still further. In another 100 containers, we are exposing them to continuous temperatures of 32 degrees.

Once an experiment has been set up, it means that my team has to monitor, clean, and feed the algae several times a week. For one to two years! Including at Christmas and during the summer vacations. Evolution may be beautiful, but it takes time! Usually, we only finish the experiment after 300 generations.  And sometimes, in the end it turns out that the algae were unable to permanently adapt to the test factor and struggled to thrive. An important insight, but rarely one that makes us do a victory dance.

Couldn’t we get the algae to adapt in a shorter time? I wanted to try out a new method out for the first time: Instead of introducing the Thalassiosira to the changing conditions gradually, I put them on a rollercoaster. In a further series of experiments, I immersed them in alternating baths – warmer, cooler, warmer, cooler. Every four days I turned the thermostat up from 22 to 32 degrees, then after another four days turned it back down again. Could they tolerate this?

The surprising answer: Yes, very well! The results were impressive, demonstrating that while the algae in constant 32-degree modus were   unable to cope with the heat and developed poorly for about a year, they were able to tolerate the same temperature in fluctuating modus without any problem. The population came to life – like at 26 degrees – and grew quickly. Faster even than at the usual 22 degrees. Our analyses also show that the genetic changes in Thalassiosira are greatest in fluctuating conditions.

An unstable environment promotes genetic adaptation in algae – a groundbreaking discovery. This means that they are better equipped to adapt to future extreme situations. A positive side effect: Our experiments can be shorter.

For the moment we don’t have to worry about the flexible diatoms. Instead we need to keep an eye on their predators, which may not be able to adapt as quickly. With their versatility, the algae appear to always be one step ahead. 

This content was first published as a guest article in the newspaper Hamburger Abendblatt in September 2018.

Elisa Schaum is an evolution expert at Universität Hamburg’s Center for Earth System Research and Sustainability (CEN)

Go to whole Abendblatt-series.

Taking a closer look at our oceans

17. August 2018 - 10:21

According to the targets set by the European Union, by 2020 our oceans are meant to be clean, healthy and productive; a laudable goal. In order to reach that goal, the EU’s individual Member States have to first know what state the oceans are in. How can they best find this information? And how can they translate what they learn into suitable measures and policies? These are the types of questions that my colleagues at Universität Hamburg’s Center for Earth System Research and Sustainability (CEN) and I are currently investigating.

The EU has subdivided the ecosystem “oceans” into various components: just like a doctor, who examines a patient’s cardiovascular system, digestive tract and immune system separately. In turn, the EU has defined the ideal state for each component.  For example, there should be a diverse range of flora and fauna, and as many edible fish as possible. In addition, all parts of the food web – animals, plants, bacteria and many more – should be sufficiently abundant to ensure their long-term survival.

The food web also includes all predator-prey relations: fish feed on microorganic fauna called zooplankton, which in turn feed on algae. Bacteria feed on and decompose all dead organic material. The component ‘food web’ is an important one in terms of assessing the overall state of the oceans. Nevertheless it remains difficult to find indicators that offer clear information on the oceans’ status. For human beings, body temperature is a good indicator: if it’s too high, we know the person in question has a fever – and their health status is poor. 

We tested 13 common indicators for three regions of the Baltic Sea. Scientists frequently use all 13 to assess the status of the food web – but are they actually suited to the task? Seven of the indicators concern fish; the remaining six focus on zooplankton: How many are there? And how large are they on average?

To determine how well the indicators work, we’ve developed a computer model, which we supply with data on the indicators, and on environmental influences like climate change or overfertilization. A good indicator shows us the current state of the food web, and can quickly and clearly react to specific environmental influences. If the zooplankton are becoming smaller on average, it indicates that the food web is in poor shape. One possible cause is overfertilization – if we can verify this connection with proof, the remedy is clear: less fertilizer in the water. 

Despite countless calculations, there’s no such thing as a single, universally applicable indicator. For example, the total amount of zooplankton was a good indicator for the state of the food web in the Bornholm Basin and the Bothnian Sea between Sweden and Finland, yet proved wholly unreliable for the Gotland Basin. Further, in the Bornholm Basin the average size of the zooplankton showed only a minimal change in response to certain environmental influences. Depending on the region, up to half of the indicators failed to respond as expected to changes in the environment. For the Bornholm Basin, six of the indicators proved to be suitable for evaluating the status of the food web; for the other two regions, other combinations proved to be a better fit. 

Accordingly, suitable indicators have to be selected for each individual region. Our model can help members of the research and political community to identify the best candidates, ensuring that it will be easier to assess the state of our oceans in the future – the first step toward achieving the goal of cleaner and healthier oceans by 2020. 

This content was first published as a guest article in the newspaper Hamburger Abendblatt 13th of August 2018.

Dr. Saskia Otto is a biologist and works at Universität Hamburg’s Institute of Marine Ecosystem and Fishery Science. 

Go to whole Abendblatt-series.

Fresh business ideas on climate change

16. August 2018 - 12:33

The members of the Journey that started in Hamburg are using the two weeks there to learn more about the background of climate change and to gain insights into starting a business. Experts from the Cluster of Excellence CliSAP and the Center for Earth System Research and Sustainability (CEN) shared their knowledge, supported by external speakers from the Max Planck Society and the Helmholtz Zentrum and meetings with regional and succesfull green start-up founders. Trips to the German Climate Computing Center and the Startup Dock rounded out the program. Inspire, share and meet – these were the key words.

After two intensive weeks, the first drafts for business ideas are now ready. In the subsequent two weeks in Helsinki (Finland), the teams will develop these into viable business concepts and fine-tune their business projects. The final week of the Journey, in Valetta (Malta), will culminate in pitching this idea to an expert jury, which then selects a winner. The winning team and their plans for implementing the idea and starting their own business will be presented here in September.

See pictures of the teams and tehir ideas here.

Climate Adaptation Begins in the Mind

9. August 2018 - 13:07

A storm is raging on the coast of Cornwall. My interviewee John and I are standing on a rise, looking out at the Atlantic. Storms are common in Cornwall, yet the high frequency of extreme weather has begun troubling the locals. Pointing with his finger, John yells over the crashing waves, “You see the stairs over there? They used to go all the way down to the beach, but a storm washed them away. Now there are only fifty centimeters to the brink. Soon the access road to the headland will crumble into the sea!”

John works for the National Trust, an organization dedicated to preserving nature and culture in Great Britain, and is tasked with keeping that from happening. This stretch of coastline is called Godrevy, and was formed during the last ice age, more than 10,000 years ago. The cliffs consist of soft sediment, deposited by glacial rivers, and pose a major challenge for John: the coast is increasingly being washed away by the sea. In the course of the past few decades, this erosion has accelerated, and the edge is now retreating half a meter inland every year. The National Trust attributes the rapid erosion to climate change and is currently seeking adaptation measures to preserve access to Godrevy. There’s a great deal at risk; though the headland isn’t populated, it’s one of the most popular tourist destinations in Cornwall. Visitors take their families there to hike, catch a bit of sun, or go swimming; after all, Godrevy offers unspoiled nature, the sea, and an escape from the daily grind.

To ensure that Godrevy remains accessible in the future, the National Trust plans to relocate a street and two parking lots farther inland. In this regard, John has been involved in negotiations with various local stakeholders for the past ten years. For example, the organization Natural England has classified Godrevy as a nature conservation area; an association for the preservation of visual aesthetics is more focused on preserving Godrevy’s natural beauty, while another initiative wants to protect the local dune system. To make matters even more complex, the area is actively farmed. This constellation of conflicting parties and interests makes adaptation difficult, and makes the negotiations on the new infrastructure a painfully slow process. Yet the coast continues to erode, and adaptation is desperately needed – so why haven’t they been able to find a compromise in the past ten years?

In my dissertation, I explored precisely this question. Here, the example of Godrevy is part of a broader context: our climate is changing; that’s the internationally recognized consensus of scientific opinion. In this regard, human beings are both partly responsible for climate change, and are directly affected by it. Droughts can ruin harvests, storms can sweep away entire villages, and coastal areas are increasingly subject to flooding. And climate change will also have consequences for Europe. In areas where it produces particularly extreme changes, adaptation measures have to be developed. But despite the urgency, in many cases adaptation is delayed. Why?

For one thing, costs are certainly an important aspect. Yet the real barrier is often to be found in our minds. Many studies from the past several years show: simply being aware of environmental problems rarely leads to a solution, and findings on the causes and potential consequences of climate change only slowly translate into societal and political action. Beyond technical considerations, it’s the social norms and values, anchored deep in every one of us, that shape our actions. These values can vary considerably, e.g. between European and Asian cultures. Yet even within our western societies, phenomena like climate change aren’t always perceived in the same way. Further, the actors involved often have various goals and interests. Conservationists have different priorities than city planners; the tourism and agricultural sectors often clash. Further, the local context and the history of a given area are extremely relevant. All of these factors determine how we perceive climate change, and whether or not we decide to actively address it.

The goal of my research was to determine how these disparate perceptions affect the implementation of adaptation measures. As a geographer, for me the focus was on those values that concern the interactions between humans and their environment. What perspectives do people have on nature and the landscape, and how do these perspectives shape the various approaches to climate adaptation? To find answers to these questions, I traveled to Cornwall and interviewed local actors who are responsible for adaptation to the coastal erosion. The interviewees represent a range of social groups: organizations like the National Trust, municipalities, farmers, and nature conservation lobbies.

How human beings perceive climate change isn’t something you can test in a lab. For the purposes of my work, I selected an unconventional method: what are known as walking interviews. Classical interviews normally take place in an office; walking interviews take place outdoors. Equipped with a recorder and microphone, I let the interviewees lead me on walks along the coast – an approach that gave me insights into their personal perspectives on Godrevy and climate change, on the landscape, nature, and on how to best adapt to the erosion. By trying to see things through their eyes, I came to understand why the different actors are so far apart when it comes to climate adaptation.

It’s now mid May, and I’m standing once again on the coast of Cornwall. This time I didn’t invite John for an interview, but Emma instead. Today, Godrevy is shining in all its splendor: an azure sky above, and a turquoise, calm sea below. Emma works for the nature conservation organization Natural England. What she has to tell me about Godrevy and climate change sounds very different from what John said. As she explains, “Coastal erosion is perfectly natural, and good for the ecosystem.” She doesn’t see any need for adaptation measures, especially since they would only worsen the true problem at Godrevy: the droves of tourists, who harm the landscape and disturb the sensitive local fauna. The interviews make one thing clear: here, the word ‘landscape’ has very different meanings for different people. For John, Godrevy is a tourist landscape, and his priority is to keep it accessible. For Emma, the most important thing is to protect the fragile ecosystem and keep the harm done by tourists to a minimum. In my talks with further local actors, I learned that there were plenty of other views on Godrevy’s landscape: for some, the chief aspect is the coastline’s beauty. They see climate change as a threat to the ‘unspoiled’ nature. Accordingly, it is important to them that any adaptation measures be visually unobtrusive. Others primarily view Godrevy’s landscape in the context of agriculture and efficiency. For them, the goal of climate adaptation is to increase agricultural production, not to preserve natural beauty or protect certain animal species.

The concrete suggestions on how to preserve Godrevy’s infrastructure vary just as widely as the standpoints regarding its landscape. The National Trust wants to shift the street inland and preserve the parking lot. Natural England, in contrast, feels there is no need for a parking lot. On the contrary: the erosion is a natural process, they claim, and should be supported. At first blush, this lack of consensus is confusing, since all of the local actors want to protect Godrevy’s landscape from the effects of climate change. Yet they all have different definitions of ‘landscape’ and ‘protect.’ For some, landscape means the coexistence of humans and nature, and tourism is a desirable thing; for others, landscape refers to a mosaic of flora and fauna that human beings should protect and preserve. As a result, the opinions on how to respond to coastal erosion are correspondingly disparate.

My research clearly shows: both ‘landscape’ and ‘climate change’ mean many different things to different people. There may be a broad consensus on how climate change is transforming our planet, but how these effects are perceived and judged by local actors can vary considerably. Whether or not a given person is prepared to take action with regard to climate adaptation depends to a great extent on precisely these individual perspectives. In the case of Godrevy, this has resulted in lengthy negotiations over how to respond to the retreating coastline. The only way that we’ll succeed in finding appropriate measures for places like Godrevy that will be accepted and actively supported by everyone involved is by understanding these local contexts and taking them into account in political adaptation strategies.  

Vera Köpsel investigated the coasts of Cornwall in 2016, and subsequently completed her doctoral studies at Universität Hamburg’s Cluster of Excellence CliSAP (Integrated Climate System Analysis and Prediction). At the CEN, she is currently responsible for Stakeholder Engagement and Public Relations in connection with PANDORA, an EU project exploring sustainable fishing management.

The Hamburg Code for global warming

30. Juli 2018 - 13:07

The data Franzke used came from the “European Climate Assessment & Dataset Project.” For Fuhlsbüttel, the records reach back for 127 years – much farther than in most other districts; for e.g. Bergedorf, the mean annual temperatures only date back to 1966.

The year with the highest mean temperature to date was 2014 with 10.7 degrees Celsius, nearly two degrees above average; the coolest year was 1940, with only 6.7 degrees. Further, there is an abrupt climb starting in 1990: from this point on, nearly every stripe is red; in other words, the annual mean temperature was nearly always above average. According to Franzke, who is an expert statistician, “That’s definitely no coincidence. The rise in temperatures is statistically significant and can’t be explained by natural fluctuations.”

Ed Hawkins from the University of Reading created the first climate bar codes only a few months ago. The idea has since caught on worldwide, and can even be seen on ties and coffee mugs.

Ed Hawkins’ Visualization Lab
European Climate Assessment & Dataset Project
More climate visualizations

International Summer School: Experiencing climate research firsthand

19. Juli 2018 - 12:06

Kevin Thellmann from Stuttgart is currently pursuing his doctorate in Agricultural Sciences at the University of Hohenheim. He already holds a Master’s in Earth System Science and a Bachelor’s in Renewable Resources and Bioenergy (BSc).

“In my dissertation, I model ecosystem services: natural processes that greatly benefit human beings, like bees pollinating flowers. Ideally, in the future I would like to integrate climate change into my models, since it affects many of these processes. That’s not going to be easy – I’ve already learned that much (laughs). That’s why I’m especially looking forward to the last week of the Summer School: then we’ll use two different models to practice modeling the climate and interpreting the results.”

Liisa Andersen is currently writing her dissertation in Immunology at the Medical University of Vienna. At the same time, she has begun a Master’s degree program in Environmental Science.

“I personally find climate change an amazing topic, because its unprecedented, global and all-encompassing scale makes it truly unique. In my opinion, climate change is the first problem humanity has faced that can only be solved if all academic disciplines, plus the political and commercial sectors, do their part. As such, what I most enjoy about the Summer School and the research conducted here in Hamburg is the interdisciplinarity – it’s fascinating to see how experts from a broad range of fields join forces here. You can also see this in our group: it’s highly diverse and international. At first I was a bit concerned that, because of our different backgrounds, the content would only be covered very superficially, but just the opposite is true: the quality of education is outstanding. I’m confident that much of what I’ve learned here will benefit me in my future career.”

Stefan Bergmann from California is currently working on a part-time working professional Master of Business Administration degree at the University of California Davis. He has a Master of Science in forest resources.

“I am particularly interested in social businesses, environmental and forest issues. Therefore, climate change is an important—if not the most important—topic. In my current job as certification forester it does not yet play an important role—I would like to change that in the future. What I like best about the program of the summer school are the different field trips. During these trips, for example to Himmelmoor, we get to see research on the ground. For the following days, I am looking forward to the trip to the North Sea. It is my first time in Germany and I have brought my son with me. Together we are enjoying the time in Europe.”

Additional information

The Summer School “Climate Change 2018” will take place from July 2 to 27, and will be co-hosted by the Center for Earth System Research and Sustainability (CEN), Max Planck Institute for Meteorology and German Climate Computing Center (DKRZ). Undergraduate students, PhD candidates and young professionals from Europe, Asia and America will come together for a look behind the scenes of climate research. The Summer School is especially intended for young scientists, Master’s students and PhD candidates with a solid background in the geo- or Earth system sciences, including physics and mathematics.

The Summer School is part of the “Hamburg International Summer Schools” program, which was launched in 2017 by Universität Hamburg’s International division and is offered in close cooperation with various faculties and extra-university research institutes. The portfolio, which includes e.g. the Summer Schools “Health Economics 2018” and “Particles, Strings & Cosmology 2018,” is especially oriented on the needs of international students and researchers, and introduces them to Universität Hamburg’s primary research areas.

Climate Change Summer School 2018 (Englisch)

Stressed street trees: Lindens, oaks, or maples facing premature death in the future

16. Juli 2018 - 11:27

From glacial materials and recent sedimentation—for instance, due to the Elbe’s tidal conditions—about 30 different soil types have developed, representing almost all soils occurring in Germany. Very few people have heard their names: Regosol, for example, is a plain, carbonate-poor soil, whereas Podzol is acidic and sandy, and Gley groundwater-saturated.

Together with my team from the Center for Earth System Research and Sustainability (CEN) at Universität Hamburg I am exploring how the various soils react to climate change and how their roles in the ecosystem and human well-being are altering. The rising temperatures and longer dry spells in summer predicted for North Germany will dry out local soils with poor water storage and transmission abilities such as the sandy areas of the Lüneburg Heath. Dehydration will also make them susceptible to wind erosion. More extreme rainfall may effect waterlogging in the less permeable soils in northeast Hamburg — plus water-induced erosion.

These changes will also impact the City’s vegetation, particularly urban trees. They are already forced to withstand difficult conditions: A warmer local climate than in the countryside, higher pollution levels, and sealed, compacted soils. Currently, 60 percent of urban Hamburg are covered by settlements and areas constructed for traffic, more than one third is sealed.

My team and I collected soil samples across the city and analyzed them. In 9 out of 10 places we found substances dumped by humans, mostly mineral-poor sand that can scarcely store any water. Almost every third sample contained building rubble, waste, slag, and ashes.

Young trees can hardly grow roots in such soils. Thus, street tree seedlings are often placed into pits with a planting depth of 1.5 meters. But these pits will soon be too small; after all, a tree root system requires about as much space as its visible part, its crown. If tough conditions worsen on account of climate change, future street trees will be prone to short life spans. We expect newly planted trees to last no more than 40–50 years.

This would be tragic for Hamburg. No prospect of regrowing a well-established stock of trees; a dramatic loss, as ancient and mighty linden, oak, or maple trees help humans thrive by producing oxygen, providing shade, and cooling their surroundings through evaporation.

Hence, I am investigating how we can improve living conditions for trees in urban settings. We need, for instance, suitable growing mediums for planting holes which can store or drain water as needed. Assigning specially trained soil guards to roadside construction sites might help, too. We should all learn how to better protect and value soils; they are the bread and butter of plant life and animals aplenty—an all-too-exhaustible resource.

This content was first published as a guest article in the newspaper Hamburger Abendblatt in July 2018.

Annette Eschenbach is a professor of soil protection and soil technology and a member of Universität Hamburg’s Center for Earth System Research and Sustainability (CEN).

Go to whole Abendblatt-series.

OceanRAIN project collects unique data on precipitation over the world’s oceans

10. Juli 2018 - 11:19

Over the past seven years, Christian Klepp has installed specially developed devices on board eight research ships to record the along-track precipitation. To date, the devices have gathered more than 6.8 million individual measurements, which were also used to calculate evaporation. The difference between the two values (precipitation and evaporation) tells us how much water evaporates from the oceans and how falls back into them – an important parameters for climate models.

In the past, these models used data from satellites. However, Christian Klepp’s dataset allows for the first time to verify and calibrate this satellite-based information; e.g. that provided by NASA’s Earth observation satellite program Global Precipitation Measurement (GPM).

Fundamentally speaking, information on the global water cycle is important for two reasons: On the one hand, many researchers believe that climate change will change the amount, spatial distribution patterns, and extremes of precipitation. Accurate measurements can help us to verify this theory.

On the other hand, understanding the links between precipitation and vertical air motion yields insights into how local and global air circulation interact. This interaction is likely to have a significant influence on climate sensitivity; in other words how much increased CO2 levels in the atmosphere affect the temperature at the Earth’s surface.  

Researchers can access OceanRAIN data online via the ICDC (Integrated Climate Data Center) and the WDCC (World Data Center for Climate).

Link to article: 

35 years of marine conservation: the lack of a strategy increases the need for protected areas

27. Juni 2018 - 14:25

International agreements like the Sustainable Development Goals (SDGs) and the United Nations (UN) Aichi Biodiversity Targets specify that, by 2020, at least ten percent of the world’s coasts and oceans are to be protected areas – and today, with ca. 16.8 percent, that goal has already been reached. Further, the areas protected weren’t chosen at random: a further specification is that all marine habitats be included, in an effort to stem the loss of biodiversity around the globe.

Together with experts from the University of Queensland, Australia, the environmental researcher Kerstin Jantke analyzed marine protected areas, from their origins in 1982 to 2016. In this regard the team only examined national waters (39 percent of the total ocean), as international waters have proven difficult to protect. These national waters consist of 258 ecoregions – comparatively large areas that can be geographically demarcated on the basis of their local species and environmental conditions. For each region, ten percent should be protected. Yet the study shows that more than half of the ecoregions (157) are not sufficiently protected; ten of them aren’t protected at all.

It is particularly important that these areas be strategically selected in the future. The team compared their size from year to year, and simulated an optimal expansion of protected areas. If tactical planning had begun in 1982, only 10.3 percent of the national waters would have sufficed; in 2011, 13 percent would have been enough to provide the agreed-upon ten percent protection for all ecoregions. As such, the goal could have been long-since reached and the follow-up costs, e.g. those resulting from limitations on fishing, would have been far lower.

“The individual countries need to proceed systematically and pursue strategic collaborations. Only then can we address the massive gaps in the current system,” says Jantke. “But in most cases, national and commercial interests are what come first. In the future, first of all new protected areas need to be established in the less-protected ecoregions.”

In 2020, new nature conservation goals will be negotiated in China, under the auspices of the UN. Many experts believe the future of a given ecoregion can only be safeguarded if at least 30 percent of its area enjoys protected status. As Jantke explains, “I’m in favor of protecting additional areas. After all, biodiversity is essential to our livelihood. Another aspect to consider is that, even if these areas aren’t completely immune to climate change, their protected status improves their chances of adapting to new climatic conditions.” The current study lays the groundwork for a future approach to marine conservation that is more systematic. 

Original article: Jantke K., Jones K.R., Allan J.R., Chauvenet A.L.M., Watson J.E.M., Possingham H.P. (2018): Poor ecological representation by an expensive reserve system: evaluating 35 years of marine protected area expansion. Conservation Letters, DOI: 10.1111/conl.12584

Images for download:
Photo: Great Barrier Reef ©UHH/CEN/K.Jantke
The Great Barrier Reef in Australia, one of the 258 marine ecoregions examined
Map: Protection of ecoregions ©K.Jantke
The chart shows the ecoregions in 2016, light grey = 10% or more protected, dark grey = less than 10% protected, red = no protection. Ecoregions not sufficiently protected (dark grey) are mostly found in the marine areas of densely populated countries.

Dr. Kerstin Jantke
Center for Earth System Sciences and Sustainability (CEN)
Universität Hamburg
Phone: +49 40 42838 2147

Stephanie Janssen
Outreach CliSAP/CEN
Center for Earth System Sciences and Sustainability (CEN)
Universität Hamburg
Phone: +49 40 42838 7596

Hamburg-based “agents” in the service of climate research. Agent-based modeling allows researchers to simulate human behavior.

27. Juni 2018 - 13:21

Day in and day out, Bob, Alfred and Earl commute to work in Hamburg’s Hoheluft district, bring their children to the daycare, or go shopping. But they don’t actually exist. They are “agents,” who move through a virtual Hamburg in a computer model. My team and I use this model to explore how agents’ typical living situations and attitudes influence e.g. their choice of commute: Bob doesn’t have much time, Earl doesn’t have much money, and Alfred is very environmentally aware. In addition, factors like the weather, gasoline and bus prices shape their decisions.

Thanks to the model, we can also estimate how the agents are affected by “environmental stresses,” i.e., by environmental factors that are potentially harmful to their health, like heat, noise, air pollution or the impacts of climate change. In cities characterized by a high density of people, buildings and traffic, these stresses are especially dangerous: around the globe, air pollution alone is responsible for an estimated two million deaths every year. Further, because buildings store heat, extreme heat waves — which are likely to become more frequent in the future — can make cities far warmer than the surrounding countryside. 

More than half of the global populace already live in cities, and that number is rising. For urban planners and politicians, making cities healthy and worth living in is a key priority. And the insights that we glean from agent-based modeling can help them achieve that goal. On the computer we can experiment to see how annoying construction sites, rising costs for public transportation, or additional bike paths affect the choices of individual citizens – and what that means for their health, and for the health of the city as a whole.

The method was made possible by the rise of computers. I first took advantage of it for my doctoral dissertation in 1989, where I used a self-programmed model to simulate the outcomes of various scenarios in the East-West conflict. Given the two main possibilities — escalation and de-escalation — my model predicted that growing trust between the two superpowers would likely produce a chaotic transitional period. And, just a few weeks after the simulation, the cold war ended with the collapse of the Eastern Bloc. Even I was amazed to see how quickly the reality caught up with my forecast.

Today, agent-based modeling has become indispensable for researchers. If our goal is to understand how a specific group will behave in a given setting, the method can offer valuable insights. It’s also well suited to researching the effects of urban environmental stresses — as the test with the representative agents Bob, Alfred and Earl shows. The results produced to date have laid the groundwork for expanding the model using real-world behavioral data. We could then e.g. simulate the consequences of extreme weather events, to determine whether or not urban evacuation and supply routes actually work as they should in a crisis. Another possibility would be to apply the method to other metropolitan areas – after all, cities around the world have to adapt to climate change.

This content was first published as a guest article in the newspaper Hamburger Abendblatt in June 2018.

Jürgen Scheffran is a Professor of Integrative Geography and a member of Universität Hamburg’s Center for Earth System Research and Sustainability (CEN), where he leads the Climate Change and Security (CLISEC) research group and presents joint modeling outcomes from the URBMOD project.

Go to whole Abendblatt-series.


Liang Emlyn Yang, Peter Hoffmann, Jürgen Scheffran, Sven Rühe, Jana Fischereit, Ingenuin Gasser (2018) An Agent-Based Modeling Framework for Simulating Human Exposure to Environmental Stresses in Urban Areas. Urban Science 2, 36. Read Online.

Todd BenDor and Jürgen Scheffran: “Agent-based Modeling of Environmental Conflict and Cooperation” will be released in September 2018 by Taylor & Francis.

Is there a specific Hamburg approach to climate science?

26. Juni 2018 - 12:32


Prof. Dr. Jochem Marotzke
Prof. Dr. Martin Claussen
Prof. Dr. Johanna Baehr
Prof. Dr. Beate Ratter
Prof. Dr. Hermann Held

Moderation: Prof. Dr. Anita Engels

Monday, 9.7.2018
6:30 p.m.

Heilwigstrasse 116
20249 Hamburg

Internal event for CliSAP and CEN. This event takes place in English.

Invitation (pdf)




Der Hamburg-Tornado vom 7. Juni 2016 – Vorhersage wäre möglich gewesen

11. Juni 2018 - 10:57

Meteorologe Dr. Peter Hoffmann: „Als ich an dem Tag von der S-Bahn nach Hause ging, habe ich das Gewitter gesehen. Es war nicht weit entfernt, ich schätze etwa drei Kilometer. Normalerweise wäre ich stehen geblieben und hätte gewartet, um mir das Schauspiel anzusehen. Denn ich bin auch Storm Chaser und habe in Texas, USA, einmal einen Tornado live gesehen. Aber ich wollte nach Hause, zu meinem kleinen Sohn. So habe ich den Tornado vor meiner eigenen Haustür tatsächlich verpasst!
Hätte ich das nur vorher gewusst. Ich erinnerte mich dann an das Rechenmodell zur Wettervorhersage, mit dem ich während meiner Zeit in Australien gearbeitet hatte. Es ist frei verfügbar, ich hatte es auf meinem Laptop installiert und probierte es kurze Zeit später aus: Die Vorhersage für Hamburg sah vielversprechend aus!“

Zur gleichen Zeit zeichnete auf dem Dach des Geomatikums der Universität Hamburg das Regenradar den Tornado detailliert auf. Für die Meteorologinnen und Meteorologen vom CEN ein seltener Glücksfall, dass er sich im Einzugsgebiet des Hamburger Radars befand.

Meteorologe Prof. Felix Ament: „Unsere Radarbilder sind die einzigen professionellen Aufzeichnungen, auf denen der Tornado im Detail zu sehen ist. Weil nur wenige Gebiete weltweit von hoch aufgelösten Radaren beobachtet werden, verpassen wir diese Ereignisse in der Regel. Von vielen gibt es dann nur Handyvideos im Internet. Durch die wissenschaftlichen Aufzeichnungen wissen wir jetzt genau: Der Hamburg-Tornado dauerte 13 Minuten und legte eine Strecke von 1,3 Kilometern zurück.“

Der Tornado wurde mit der Stärke F1 auf der Fujita-Skala (F0-F5) bewertet, ein eher leichtes Ereignis. Obwohl er in einer dicht besiedelten Gegend auftrat, entstanden nur Sachschäden. Peter Hoffmann passte das bestehende Vorhersage-Modell namens CCAM (Conformal Cubic Atmosphere Model) in mehreren Rechenschritten so an, dass es den Niederschlag mit einer Auflösung von einem Kilometer Maschenweite wiedergeben kann. Startet man das Modell mit den Informationen aus der Nacht vom 6. auf den 7. Juni, 2 Uhr, kann es eine Gewitterzelle über Hamburg gegen 17 Uhr nachmittags mit Potenzial zu einem Tornado vorhersagen. Doch wie exakt ist diese Prognose?

Der Vergleich mit den hoch aufgelösten Daten des Radars vom Geomatikum zeigt: Das Modell hätte das Ereignis bis zu zwölf Stunden vorher, zeitlich auf eine halbe Stunde genau und räumlich mit nur etwa drei Kilometern Abweichung vorhersagen können. Mit einfacher Technik lassen sich also bereits erstaunlich exakte Ergebnisse erzielen. 

Ob sich vorhergesagte Gewitterzellen tatsächlich zu einem Tornado entwickeln, lässt sich aus dem Modell nicht ableiten. Tornados entstehen aus Superzellen, das sind hoch strukturierte Gewitterzellen, die rotieren. Doch Studien aus den USA zeigen, dass sich nur aus 26 Prozent aller Superzellen auch tatsächlich ein Tornado bildet. Für Europa wurde dies noch nicht untersucht. Zur genaueren Analyse müssten kurzfristig aktuelle hoch aufgelöste Radardaten einfließen. Ament und Hoffmann haben gemeinsam mit den Kolleginnen Claire Merker (CEN, MeteoSwiss Zürich) und Katharina Lengfeld (Deutscher Wetterdienst) nur dieses einzelne extreme Ereignis untersucht, für routinemäßige Vorhersagen ist weitere Forschung nötig – Potenzial dafür ist eindeutig vorhanden.

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Dr. Peter Hoffmann, CEN, Universität Hamburg (bis 04/2018)
Climate Service Center Germany, GERICS (ab 05/2018)
Tel.: 040 226 338 457

Prof. Dr. Felix Ament, CEN, Universität Hamburg
Tel.: 040-42838 3597