Scenario Development

Developing Plausible Climate Futures for Hamburg 2050

Contact:  Dr. Franziska S. Hanf (UHH),  Linda Meier (UHH), Dr. Marita Boettcher (UHH), Dr. Benjamin Poschlod (UHH)

To contribute to answering the overarching CLICCS research question “Which climate futures are possible and which are plausible?” in context of climate change adaptation, water from 4 sides and sustainable urban development, the C1 project explores possible and plausible climate futures for the city of Hamburg. Thereby, C1 integrates social and natural sciences as well as qualitative and quantitative approaches to construct plausible climate change adaptation options.

Possible adaptation scenarios for Hamburg 2050 - Opening up the realm of the plausible:

We started the scenario building process with a qualitative approach. By asking “what could happen?” (Vergragt and Quist 2011, Spijkers et al. 2021) but also “what should happen?”, we escape deterministic forecasts of the future (“what will happen?”) and explore the tension between possible and desirable futures in order to open up the possibility range of uncertain futures. With this approach we attempt to explore the unforeseeable from the present to create scenarios that reflect possible futures irrespective whether they are desirable. The purpose of the scenarios is to trigger societal questions such as: what are desirable urban water futures, and how can we avoid undesirable trajectories?

In fact, we developed a set of three possible scenarios of the future by means of different climate adaptation strategies (i.e. coping, incremental, and transformative adaptation) for Hamburg 2050 (Hanf et al. 2024, accepted). For each scenario, we developed a narrative that takes into account the interdependencies of the water issue with other fields of the urban system of Hamburg. In addition, the narratives were professionally visualized to test new ways and means of communicating the “wicked problem” of climate change adaptation in urban areas through stakeholder dialogues.

Physically plausible future Hamburg-Lohbrügge events - Storyline approach:

Short-duration convective heavy rainfall events, such as over Hamburg-Lohbrügge in 2018 will be altered by a changing climate. Hence, applying a storyline approach, we want to generate a physically plausible future “Lohbrügge event”. Therefore, we analyze high-resolution climate simulations over northern Germany of present and future climate to identify and quantify the influence of a warmer climate on the intensity of convective extreme rainfall. Applying these changes on the experienced event under physically plausible constraints enables us to create a storyline for a future extreme event.

Scenario Matrix - Combining qualitative and qualitative scenario approaches for Hamburg-Lohbrügge:

The next step towards developing plausible adaptation scenarios for Hamburg-Lohbrügge is to combine the qualitative and quantitative scenario approaches. To numerical model possible adaptation futures in combination with physically plausible climate futures of Hamburg-Lohbrügge area, we will elaborate a 3x2-scenario matrix with the two axes structured as follows: (1) possible adaptation scenarios - ranging from coping to transformative adaptation and (2) physically plausible climate futures - ranging from present to future climate. The objective of this study is to quantify the effects of different adaptation measures on the heavy rainfall event Hamburg-Lohbrügge 2018 in the present and future climate.

References:

Spijkers, J., Merrie, A., Wabnitz, C. C. C., Osborne, M., Mobjörk, M., Bodin, Ö., Selig, E. R., Le Billon, P., Hendrix, C. S., Singh, G. G., Keys, P. W., Morrison, T. H. (2021). Exploring the future of fishery conflict through narrative scenarios. One Earth 4(3), 386-396, https://doi.org/10.1016/j.oneear.2021.02.004.

Vergragt, P.J. and Quist, J. (2011): Backcasting for sustainability: Introduction to the special issue. In Technological Forecasting and Social Change 78 (5), pp. 747–755. DOI: 10.1016/j.techfore.2011.03.010.