In conversation with Lisa Thalheimer: uncovering the human fingerprint in climate disasters

  • 2023•03•16     Bonn, Germany

    © UNU-EHS / Lisa Thalheimer

    Lisa Thalheimer is a senior researcher at UNU-EHS. Her research focuses on the links between extreme weather and climate change and resulting human responses such as migration and displacement: climate mobility in short. Lisa is part of an international scientific initiative called World Weather Attribution, a group of scientists working on attribution science.

    Can you explain the concept of attribution for us?

    The public and the media often ask: “Does that drought, fire or storm we just lived through have anything to do with climate change or human activity? And if so, how much?” Scientists wondered what would happen if they could uncover the human fingerprint in a climate disaster. This is exactly what attribution science does. It measures how climate change affects extreme weather events by tracking changes in the environment, the oceans, glaciers, forests and the atmosphere. Many factors drive the frequency and severity of extreme weather events and socio-economic impacts. Attribution science checks a list of possible explanations using computer models and lots of data. These are also used to compare what changes have happened and what could happen in the future regarding climate change impacts.

    We can think of attribution science with an analogy of a smoker’s risk to develop lung cancer. Public health officials look at groups of non-smokers and groups of smokers to understand how their change in risk evolves. In this analogy, the smoker is our current planet and the non-smoker an imaginary Earth on which humans are not pumping greenhouse gases into the atmosphere. Just as medical researchers can predict how smoking changes the risk of lung cancer, climate attribution delivers the tools to estimate how human-induced climate change affects the magnitude and probability of an event. For instance, the India-Pakistan heatwave and floods in 2022 caused 30 billion dollars in economic losses as well as non-economic impacts, such as the displacement of people, health impacts, and pressure on healthcare facilities. The heatwave was attributed to climate change, which made its occurrence thirty times more likely. The floods that hit Pakistan a few months after were disastrous as the country was unprepared and was still dealing with the aftermath of the heatwave. This allowed a hazard to turn into a disaster of enormous magnitude.

    Climate models help us to calculate the role climate played in an extreme event by modelling worlds with and without climate change. We tend to think of climate change as something happening in the future and in other parts of the world. It is of key importance to highlight that climate change is already happening, and that it is happening in our own backyards. It therefore affects us all, and it causes more than just the economic losses that are usually highlighted in the media. Attribution science actually helps us to estimate how much extra damage and loss climate change causes.

    Can you give an example of that?

    We observe long-term changes in climate that essentially change the occurrence of extreme weather circumstances. In addition to the occurrence, climate change affects the frequency and magnitude of these events. Sometimes this is reflected in shifts in seasons. For instance, Somalia usually experiences two rainy and two dry seasons. With the impacts of climate change, local weather conditions shift, causing more extreme dry and extreme wet events to occur.

    Another example is the estimation of mobility outcomes. In addition to economic losses, with attribution science we can study whether climate change was a decisive factor in people getting displaced from extreme weather. We can also look at people’s (im)mobility, which indicates to what extent people were able to leave affected areas. To illustrate, the Western European floods in 2021 also affected the Ahrtal here in Nordrhein-Westphalia, Germany, where my great-grandfather is from. A large proportion of the elderly population did not want to evacuate. They feared being more at risk outside their homes, although staying inside led to significant higher risks than evacuating to shelters. This is an interesting angle of mobility and human responses when being hit by an extreme event.

    How can attribution science help prevent the severity of disaster impacts?

    In the 2021 Ahrtal flood example, the event was well-forecasted. The problem of information not trickling down from the national weather service to the actual communities on the local level allowed the natural hazard to develop into a disaster. The weather warnings were not taken seriously because people did not believe that extreme weather would actually affect them personally. Additionally, another important factor was the lack of a centralized warning system that clearly outlined potential impacts and the actions people should take to limit these impacts. To prevent similar scenarios for the future, the German government used the awareness gap to develop better response plans. Education materials and a centralized app for smartphones have been developed as useful tools for the public. Through the app, people receive a notification on their smart phone with weather warnings and instructions on what to do in case of extreme weather.

    Ultimately, pinpointing the role of climate change in extreme weather events, weather shocks and resulting societal impacts helps plan for future disaster risk reduction. We can improve how we respond, increase our resilience and reduce future impacts. Developments in the field are crucial in spurring climate action. The evidence is clear and climate science tells us we need urgent action, and we can all contribute to climate action. It is up to us.