European cities are experimenting with hundreds of climate solutions, from green roofs to electric vehicles, all in the hopes of adapting to the warmer world around us. But despite more and more research on these solutions, we still only barely have an idea of what actually works in practice. That’s according to a study published in Environmental Research Letters today, co-authored by researchers at Radboud University.
The study reviewed more than 1600 papers about climate mitigation and adaption measures in more than 1200 European cities. “We wanted to identify which climate actions work best in which type of city, and what cities can learn from each other,” explains Natascha Wagner, one of the authors of the study, professor of Development Economics at Radboud University and director of the Global Data Lab .
“Something that works for a big, growing metropolis in Spain might not work for a shrinking, older town in Poland. They may face very different problems: Southern Europe is dealing with extremely high temperatures and water scarcity, while Eastern European cities are more likely to be affected by flooding and high-intensity industrial emissions”, adds Olexiy Kyrychenko, assistant professor at Radboud and a co-author. “By looking at cities with similar characteristics across Europe, policymakers can get a better understanding of what measures might succeed, because they’re already successful in comparable locations.”
However, the researchers also realized that the studies they looked at were rather fragmented. Wagner: “One study looks at electric vehicles in one specific city, while another might look at renewing the infrastructure in a different, completely dissimilar location. That makes it a lot harder to identify broader patterns, and to learn from what works.”
In addition to being fragmented, most of the studies were based on models and simulations, rather than on observations of real-world outcomes. Wagner points out that those studies often provide limited insights into the effectiveness of adaptation and mitigation strategies: “Some models are based on situations that are extremely unlikely to happen in the real world, such as a study on what would happen if the entire population of a city like Amsterdam switched to vegan food.“
If we want climate policy to be more effective, we need observational data, the researchers argue. “Many studies estimate what should happen under certain assumptions, but we have far fewer assessments of what happens on the ground. To understand possible changes, we need local data on behaviour, health, mobility and environmental conditions, for example”, says Kyrychenko. Wagner adds: “What we need now, in particular in response to the recent heat wave, is the systematic collection of observational data across cities to determine what truly works, under which conditions, and for whom. The next step for climate research isn’t necessarily about developing more new solutions, but about evaluation existing ones more rigorously.”
Environmental Research Letters
Climate mitigation and adaptation strategies tailored for different types of European cities: a typology and associated systematic review