New project: Innovative measures to strengthen climate resilience

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Extreme weather events, such as the disastrous flooding in the Ahr Valley this summer and the episodes of severe drought in Europe in recent years, leave us in no doubt that climate change is now upon us. Coping with its consequences is perhaps our most urgent challenge in the coming years. Computer-based simulations of future climate are a vital tool for assessing the potential effects of interventions aimed at moderating the impact of global warming. LMU geographer Ralf Ludwig is an expert in environmental modeling, and leader of a project in the new EU-funded research program ARSINOE. The goal of ARSINOE is to develop innovative strategies that will make a positive contribution to climate resilience in nine regions in Europe, and suggest ways to implement them. In the following interview, Ludwig talks about the simulation of extreme weather events, and his ARSINOE project in which he plans to examine how climate resilience can be achieved in Main-Franken region.

Around the time of the flooding disaster in the Ahr Valley, you published a paper on the links between episodes of extreme precipitation and flood risk in catchment areas in Bavaria. Can your simulations contribute to improved forecasts of floods?

Ralf Ludwig: Generally speaking, one can assume that the more rainfall we get, the greater the volume of run-off. But things are not that simple. We have shown that there is a threshold at which the relationship between these parameters becomes nonlinear. Levels of precipitation that exceed this limit result in extreme flooding. Each of the hydrological regions in Bavaria that we studied has its own threshold level, below which the amount of rainfall is no longer the only determining factor. This is where the nature of the land surface, and water-management policies come into play.

In the case of the tragic events in the Ahr Valley this summer, the major contributing factor was an extreme precipitation event which took place within such a short time that it was essentially impossible to prevent the resulting deluge. But with the aid of the kinds of studies that we carry out, one can try to establish where the limits lie between the urge to protect and the practically feasible. For instance, under what circumstances is it justifiable to build barriers that offer protection against flash floods? What threshold does one set for the activation of alarm systems so that people can be successfully evacuated from danger zones? – Even where infrastructure cannot be saved, early-warning systems can save lives.

The fact that extreme events are by definition rare makes projections difficult. But can any inferences be drawn from this summer’s tragic floods?

Ralf Ludwig: Certainly. The more empirical data we have on the extremes of the distribution, the better our projections become in terms of their temporal range, and the greater is our ability to distinguish between genuine climate change and natural fluctuations. This holds for this year’s extreme floods, and for the severe droughts in 2015, 2018, 2019 and 2020. We in Southern Bavaria escaped the worst, but the condition of the forests elsewhere in Germany testifies to the damage done by droughts. It’s difficult to attribute individual spells of extreme weather to the process of climate change. What one can state with complete confidence is that the sequence of extreme events we have seen in recent years cannot be explained without invoking the factor climate change.

Adapting to climate change is the central theme of the EU-funded project ARSINOE, in which you are involved. What is its aim?

Ralf Ludwig: ARSINOE is a project that forms part of the EU’s Green Deal initiative. It‘s what is known in EU parlance as an innovation action – in other words, it includes a research component, but the main emphasis is on innovations. The purpose of ARSINOE is to develop – for regions that we have identified as particularly vulnerable to the impact of climate change – innovative, systems-level solutions that will help whole sectors of the economy to adapt successfully to the consequences of climate change. In effect, we must transform the insights gained in projects like our study of extreme precipitation events into guidelines for the decision-makers responsible for implementing adaptive responses to climate change.

Who are your partners in the venture?

Ralf Ludwig: Our sub-project focuses specifically on Main-Franken, a region in which we expect periods of extreme temperatures and summer droughts in the future. Our principal partners are public enterprises – such as local utilities – and energy companies that are directly affected by the impact of climate change on water supplies. This factor is of particular relevance for firms that generate power from renewable energy sources, because – with the exception of geothermal energy – the availability of these sources is critically dependent on climatic factors. I have often found it puzzling that this link is so often overlooked. Everyone talks of the role of the energy sector in driving climate change, but there has been very little discussion of the role of climate change in the renewable energy sector.

What kinds of challenges now face the energy sector?

Ralf Ludwig: Biomass, hydropower, solar power, wind – all of these power sources are at the mercy of climatic factors. Their potential and their efficiency are critically dependent on weather conditions. So, together with a broad spectrum of users and stakeholders, we need to look for solutions that make them more resilient to climatic variation. For example, municipal utilities have begun to realize that they are approaching the limits of their capacity and need to adapt in order to avoid hitting the buffers. How can they be reconfigured for what they may need to accomplish in 30-40 years from now? How can they ensure that adequate supplies of drinking water are available, if their energy supply is entirely based on renewables and they need to recycle waste water?

What exactly is planned?

Ralf Ludwig: We want to provide the Main region with a ‘hydroclimatic’ service package. We want to give municipal utilities the tools that will allow them to simulate their own scenarios, for instance – preferably integrative scenarios that reveal the diverse effects of an intervention on the system as a whole. At present, nobody can make any decision relating to the supply of drinking water which does not have repercussions for local agricultural, ecological and energy interests. It’s already an area in which water is in short supply, and water will become even less abundant in the future.

These models are intended to find responses to climate change that are acceptable to all the parties involved?

Ralf Ludwig: Exactly, agreed solutions rather than individual fixes. – I‘m not so naive as to believe that a single project in Franken can solve all the relevant problems. In consultation with our partners, we can at least decide on the services that are really required. We need customized and simple solutions. So we will either have to adapt our models, or we agree on standardized interfaces, and users then tell us which indicators they need at what levels of spatial and temporal resolution.

In order to avoid conflicts over water allocation, we have to act promptly – in other words, now – to restructure our water policies. As well as assessing the options available in their particular areas of responsibility, decision-makers must also be empowered to take the foreseeable consequences of their actions for other regions into account. If we cannot transform conflicts of interest into synergies between diverse interests, climate resilience will remain out of reach.