Science and Innovation

M. Carme Llasat Botija is a Professor of Atmospheric Physics at the University of Barcelona (UB). Specialised in extreme weather events, climate change and hydrometeorology, her research has focused on the study of heavy rainfall, floods, and their impact on the territory. She is a member of the Adverse Weather Situations Analysis Group (GAMA) at UB, where she combines scientific research with public outreach and social awareness about meteorological risks. In addition, she promotes citizen science through projects such as Floodup, supported by the Barcelona Citizen Science Office, which involves the public in the collection of flood data. With a scientific career spanning over 30 years, she has published numerous studies and actively participates in initiatives aimed at improving climate change adaptation and the management of meteorological risk.

You have devoted much of your career to studying extreme weather events. How did your passion for this field begin, and what are you currently working on?

It all really began when I decided to study Physics. At first, a professor of Geophysics encouraged me to explore the mechanisms behind earthquakes and volcanism. However, once I began to specialise, I came across subjects related to atmospheric physics and felt more drawn to that branch of the discipline. In my fifth year of university, I took part in a research project focused on precipitation intensity, and that’s what ultimately steered me toward the field of meteorology. But it was the severe floods of October 1982 in Valencia, and those in November of the same year in the Pyrenees, that definitively motivated me to study these phenomena. It felt like the right moment to carry out research that could be directly useful to society. I wanted to identify and predict all the factors that lie behind such catastrophic floods.

Later on, I realised that the Earth–atmosphere system was more complex than I had initially thought. That this goal could serve as the driving force for many years of research. That it could even inspire the work of my PhD students — and of their own students, in turn. More than forty years later, my field of action has expanded to include other extreme weather events, the impact of climate change on natural hazards, and the improvement of public knowledge and awareness around these issues. All of this while embracing the interdisciplinary and holistic approach necessary to build comprehensive understanding that supports prevention, early warning systems, and climate change adaptation.

What is the research group you work with currently focused on?

At present, we are working on a wide range of areas, such as developing a model for predicting convective rainfall and extreme weather using meteorological radar; applying artificial intelligence and complex systems theory to forecast the impacts of heavy rainfall; analysing the socioeconomic impact of floods and coastal storms; forecasting wildfires and water resources months in advance; and developing and updating the AGORA Flood Observatory of Catalonia. The latter is the result of decades of work, systematically collecting information on all flood events that have occurred in Catalonia, along with a wealth of supporting materials aimed at raising public awareness about a risk that appears to be on the rise. Within the framework of the European project I-CHANGE, we have created the Barcelona Living Lab on Extreme Events, a participatory and co-creative initiative applying citizen science — involving public administrations, businesses, academia, the media, and society at large — with the ultimate goal of improving public habits for better climate change mitigation and adaptation.

In recent years, we’ve seen an increase in the frequency and intensity of extreme weather events. How might these changes affect us in the coming years?

One of the consequences of anthropogenic climate change is the rise in intense precipitation. Indeed, the increase in greenhouse gases causes both the atmosphere and oceans to warm. This rise in air temperature enhances its capacity to hold moisture, while the warming of both continental and maritime areas increases water vapour loss through evaporation and evapotranspiration. As a result, the amount of water vapour in the atmosphere increases. By the end of 2024, it was already 4.9% higher than the previous decade. Under these conditions, the amount of energy available in the atmosphere also increases. Together, these two factors lead to more intense and abundant rainfall, which can result in flooding. We saw this with the floods last October in Valencia, and more recently with heavy rainfall in Catalonia. Furthermore, even when catastrophic flooding doesn’t occur, such rainfall can still trigger landslides.

Climate change also affects atmospheric circulation and the formation and movement of high- and low-pressure systems. This can influence rainfall-generating conditions by increasing, decreasing or altering their timing. In the Mediterranean region, models point to a rise in the frequency and intensity of droughts, which could affect all ecosystems and productive sectors.

We must also consider temperature-related extremes, such as the increase in tropical and torrid nights, heatwaves, and marine heatwaves — all of which have a serious impact on human health and ocean life. Another direct consequence is the increased risk of wildfires. It is worth noting that, in recent decades, the burned area in Catalonia has decreased thanks to improved wildfire prevention and suppression measures. However, the burned area could double if the temperature difference relative to the pre-industrial period exceeds 3 ºC.

Barcelona is a city particularly vulnerable to the effects of climate change. What strategies or measures should we prioritise to reduce the risk of flooding?

Due to its location, Barcelona is exposed to river flooding, coastal flooding, and sudden flash floods from torrents. In the case of coastal flooding, these events are usually accompanied by wind storms. In such cases, rising sea levels will contribute to higher waves during maritime storms. Possible strategies to reduce this risk include structural measures such as dikes, as well as non-structural measures like preventing development in flood-prone areas or even freeing up land to create wetlands — as could be done in the Llobregat area. In fact, there are already numerous studies and actions addressing this issue.

On the other hand, Barcelona has been recognised by the United Nations as a “flood-resilient city”, thanks to improvements in its drainage network and the construction of stormwater retention tanks. However, a key weakness was also identified: the public’s lack of knowledge about how to act — both to reduce flood risk and to improve self-protection. Therefore, enhancing public awareness and understanding should be the first step, as it could help avoid the loss of assets located in flood-prone areas, traffic congestion during heavy rain, or ensure storm drains are kept clean. Another important point is that floods do not affect all areas or assets within a city equally, and that — even if we don’t always realise it — they continue to cause significant economic damage. To illustrate this, between 1981 and 2010, the city of Barcelona experienced 63 flood events, and between 1996 and 2014, the Insurance Compensation Consortium paid over seven million euros in flood-related damages within the Barcelona Metropolitan Area.

How does academic research translate into real-world action on the ground?

We have been collaborating for some time now with the companies responsible for the city’s drainage network. In fact, the current operator, BCASA, is part of the Barcelona Living Lab on Extreme Events. This partnership has allowed us to experience firsthand the progress, challenges, and nuances of the socio-economic framework and how it influences flood vulnerability. We have identified “storm hotspots,” the extreme variability in rainfall intensity within Barcelona, the challenges of forecasting at the urban scale, and the behavioural patterns among the population that should be changed to reduce risk. This collaboration has shown us, for example, that it would be necessary to build more stormwater retention tanks in certain strategic locations, to incorporate nature-based solutions, and to improve the forecasting and monitoring of heavy rainfall.

Do you think smart city technologies can help mitigate the effects of extreme events such as flooding? What would be their key role?

To answer this question, we first need to understand the full meaning of the term “smart city.” According to the Catalan Terminology Centre (Termcat), a smart city is defined as one “that has a solid network of telecommunications and information systems, and an innovative technosocial fabric that increases the social capital and learning capacity of the entire city, responding to economic, social, political, and environmental challenges, while placing the citizen as a central reference point.” It is a comprehensive challenge that brings together ICT, sustainability, social justice, lifelong learning, and respect for individuals.

In this context, technology must go beyond developing automated systems that decide whether to open gates in different parts of the drainage network or divert water flows based on current or even forecasted rainfall. While these are significant advances, they are not enough — and may not even be strictly necessary. It all depends on the city’s characteristics, flood-prone areas, size, the type of flooding it faces, and the feasibility of implementing nature-based solutions or combining them with structural measures.

Therefore, the first step is to thoroughly understand the city and its inhabitants, the traditional flood management strategies, the types of floods that may occur, and the areas most likely to be affected. It’s about knowing the maximum level of risk that could arise and providing people with the tools to know how to act — both preventively and during an emergency. It also involves deciding the philosophy behind the system being implemented, and defining thresholds where decisions should be made by on-site experts rather than AI or other automated systems.

This is not to say that technology isn’t necessary. Without a doubt, it can help improve every part of the process — starting with observation systems such as automatic rain gauge and hydrological networks, which provide updates every 5 or 10 minutes, and meteorological radar; continuing with short- and medium-term hydrometeorological forecasting models; and concluding with alerting the public through mobile phones, also known as “reverse 112” systems.

What research lines do you consider a priority for better understanding extreme weather events and helping cities adapt to climate change?

In general, what is now known as an early warning system can help us respond to such events. This system is based on four pillars: risk knowledge and management, observation and prediction, communication and dissemination, and response capacity. All research lines that address any of these four pillars are important, and their priority will depend on each city and the specific risk in question. However, to be effective, a multidisciplinary collaboration and an open mindset are required — one that fosters a holistic dialogue. Above all, it is essential to have a deep understanding of the city and its space-time dynamics, the extreme weather events that may affect it, and the potential influence of climate change on these events, bearing in mind that any measure to be implemented must align with climate change mitigation. In other words, it must not contribute to an increase in greenhouse gas emissions.

The GAMA research group at the University of Barcelona carries out highly relevant work in both research and outreach. How has this combination helped improve preparedness for climate anomalies?

Public response capacity is essential. This goes hand in hand with raising awareness of the role individuals play in both change and self-protection. The research we carry out at GAMA focuses on natural hazards and climate change — from building fundamental knowledge to implementing solutions — which allows us to engage in every link of the chain. Our outreach efforts have always carried a strong awareness component, grounded in a deep commitment to society and the environment.

Let me give the example of floods in the context of climate change. As part of the European project SPHERE — led by the CSIC — and later through research led by the Technical University of Vienna (Austria), we analysed floods across Europe and their evolution since the 15th century. This allowed us to detect whether there had been events more severe than those of the 20th century and to determine whether there was clear evidence of the anthropogenic climate change footprint on their intensity and frequency in Europe. The answer was yes in both cases, which calls for a potential rethinking of preventive measures and gives us stronger grounds to affirm the role that climate change is playing in the increasing frequency and intensity of floods.

The Floodup project promotes citizen science as a way to better understand flooding. What are the main challenges and lessons learned when it comes to involving the public in projects like this?

There is a common misconception that confuses citizen science with awareness-raising or outreach. In citizen science, non-scientists actively participate in a scientific research process, usually in observation or data collection. For example, in a study on complex systems, citizens might record the number and location of butterflies or tiger mosquitoes in a specific area over a given period of time. While it’s true that knowledge often leads to a kind of awareness — in the sense of “becoming aware” or “realising” — it doesn’t necessarily mean that the project’s goal is to increase environmental sensitivity. Nor is it a requirement for citizen science that participants be familiar with the latest advances in butterfly research. However, scientists who promote citizen science are often strongly committed to outreach, which frequently becomes embedded in the process.

Floodup is, in fact, a tool that brings together all three elements. It is a mobile app linked to a web platform that combines outreach, awareness, and citizen science. Through the app, users are introduced to the essential aspects of natural hazards — especially floods — as well as climate change. The platform also shares some of the latest research in the field. In this way, it helps raise awareness, encourages behavioural change, and promotes better self-protection. Moreover, the app has an interactive component that allows users to upload comments and images related to hydrometeorological risk situations, examples of good and bad practices, and more. The tool is available in Catalan, Spanish, English, French, and Basque, and allows information to be uploaded from anywhere, at any time — data that can later be used to identify hazardous situations or critical points. It is also used in specific campaigns, such as the identification and mapping of plaques and signs commemorating historical floods, the “Floodup Francolí” campaign developed after the torrential rains of October 2019, and various citizen science campaigns carried out in schools.

What could be done to improve communication about meteorological risks and raise public awareness?

First and foremost, I believe it is essential to raise awareness among citizens about the role they can play in reducing risk — both by taking preventive measures and by acting during emergency situations. We need to move from a passive mindset, which places full responsibility in the hands of third parties charged with protecting us and our property, to an active mindset that prompts us to ask: “What can I do?” Naturally, this requires a basic understanding of risk and a potential capacity for response and decision-making over the medium term. Awareness-raising efforts around weather-related risks should begin in schools — as is the case in many parts of the world — and be complemented with information made available in public spaces such as town halls, logistics centres, and so on. All of this should be supported by specific information tailored to the characteristics of each location, such as evacuation points or — as is already the case in some cities — climate shelters, so that residents know how to act when an alert is issued. Throughout this entire process, special attention must be paid to people in more vulnerable situations.

Another key area for improvement is the set of internal processes that precede or accompany public alerts. These start with meteorological, hydrological, or geological warnings (such as avalanche risk), issued directly by the relevant authority — in this case, the Servei Meteorològic de Catalunya and its hazardous weather warnings. These processes become more complex as various agencies become involved — civil protection, fire services, municipal authorities, and so on. We must also not overlook the messages that need to be communicated, how they are communicated, the channels used, and, above all, the connection with the final recipient: citizens