As the reality of a changing global climate manifests in severe flooding and intensifying droughts, the risk and preparedness for these extreme weather events is distributed unevenly worldwide. Panama City, Panama, for example, is becoming increasingly vulnerable to floods, while Amman, Jordan, is becoming more susceptible to droughts. Before local stakeholders can address these water-related vulnerabilities, however, they must know about them.

A new study from researchers at the University of Notre Dame addresses a critical gap in the development of globally comparable, usable knowledge to prioritize investment and planning to increase overall water security and reduce vulnerability to extreme events. The pilot study, published in the journal Earth Systems and Environment, developed a comprehensive, scalable method for assessing a city’s vulnerability and resilience to water-related climate trends.

The research was conducted as a part of Notre Dame’s Global Urban Climate Assessment (GUCA), a pilot tool inside of the Notre Dame Global Adaptation Initiative (ND-GAIN).

“In developing countries, not only is the data inconsistent, its reliability is limited and not suitable for rigorous analysis,” said Mohamed Aboelnour, postdoctoral scholar at Notre Dame’s Environmental Change Initiative (ND-ECI) and lead author of the study. “The challenge was to find accessible, reliable precipitation data that included all major cities across the globe, and then make sure the analysis we did was replicable.”

To address the first challenge, Aboelnour and colleagues turned to reanalysis data produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). Reanalysis data combines historical weather observations from sources like satellites, weather balloons, and weather stations with physics-based climate models to create a consistent record of past weather conditions. The team selected the ECMWF’s ERA5-Land precipitation dataset for its fine resolution and inclusion of surface water data.

“You get the many advantages of a physically based climate model implemented at global scale, combined with the reliability and specificity of on-the-ground, or in this case, in-the-atmosphere, observations,” explained Alan Hamlet, associate professor in the Department Civil and Environmental Engineering and Earth Sciences and co-author. “These global simulations of historical weather are updated regularly, and bring the data together in one self-consistent global package, including places that are typically data-scarce, or suffer from poor data quality. Reanalysis products also save time and human resources by putting everything in one comprehensive package in a common archival format.”

Replicability and city-wide comparability are crucial dimensions for the GUCA framework, a pilot decision-support tool aimed at tracking climate vulnerability and resilience for cities around the world. The GUCA pilot study selected 12 cities with varying climate and socioeconomic characteristics to explore differences in measuring climate-related hazards across contexts.

“The main goal with the GUCA pilot was to develop an approach to providing equivalent vulnerability and resilience data so that you could compare cities,” said Danielle Wood, associate professor of practice at the ND-ECI and faculty director of ND-GAIN. “Although the purpose is comparison, we’ve designed it so that low-capacity cities would have valuable core information for analysis.”

With this design aim in mind, Aboelnour and Hamlet set out to develop a water resilience index based on the selected data. In this index, flood hazard risk serves as a measure of vulnerability, and water security serves as a measure of adaptive capacity.

Changing flood hazards were quantified by analyzing changes in peak annual precipitation over time, proximity to a river or a stream, and the magnitude of the historic 25-year daily precipitation event— an extreme daily event occurring once every 25 years on average.

Water security was assessed by taking into account average annual precipitation, trends in annual precipitation, rate of population change, as well as freshwater withdrawal rates at the country scale.

To calculate the latter two dimensions, the ERA5-Land reanalysis data was supplemented with country-level data from WorldPop. Aboelnour also verified the ERA5-Land precipitation metrics with other online sources, as well as ground truth precipitation data from the National Oceanic and Atmospheric Administration (NOAA) for Berlin, the only city not in the Global South in the pilot study.

The results, published in the journal Earth Systems and Environment, can be viewed alongside other GUCA indices for the 12 cities on the pilot dashboard: Abuja (Nigeria), Amman (Jordan), Beijing (China), Berlin (Germany), Bogotá (Colombia), Jakarta (Indonesia), Kinshasa (DR Congo), Mogadishu (Somalia), Mumbai (India), Panama City (Panama), Rio de Janeiro (Brazil), and Shenzhen (China).

“We hope that the GUCA pilot can be a conversation starter for the next iteration and expansion,” Wood said. “We’re interested in collaborating with stakeholders to better understand the strengths and limitations of its applications to make it a more effective tool.”

Publications on other dimensions of the GUCA framework, including methodologies for measuring heat and governance capacity, are in process as well. Similar to Aboelnour and Hamlet’s work on water, these took into account the aim of replication and expansion when designing and implementing the pilot analysis.

“We now have a robust code structure that can pull data, run the analysis, and generate outputs for any city by simply inputting its latitude and longitude,” Aboelnour explained. “In order to make expansion feasible, replicability is essential, and we’ve done that work already.”

Wood reflected, “For more than a decade, ND-GAIN has served as a trusted data source, providing updated, reliable, and accessible information for decision-makers. We’re excited about the potential that a GUCA expansion has to become a resource for the common good by serving the needs of those investing in climate adaptation, including identifying the most vulnerable cities.”

About ND-GAIN

ND-GAIN is a program of the Notre Dame Environmental Change Initiative (ND-ECI). At ND-ECI, more than 60 faculty across several disciplines are pursuing research solutions for many of the key environmental challenges of our time. ND-ECI focuses on globally significant, multidisciplinary research that can be translated into management and policy solutions to help make the world a better place for humans and the environment upon which people depend.

The GUCA pilot is the latest addition to ND-GAIN’s already robust suite of climate tools and intervention resources, which also includes the ND-GAIN Country Index and the U.S. Urban Adaptation Assessment, a tool assessing over 270 U.S. cities’ climate risks and social vulnerabilities by neighborhood.

Contact

Erin Fennessy / Writing Program Manager

Notre Dame Research / University of Notre Dame

efenness@nd.edu / +1 574-631-8183

research.nd.edu / @UNDResearch / linkedin.com/company/undresearch

About Notre Dame Research

The University of Notre Dame is a private research and teaching university inspired by its Catholic mission. Located in South Bend, Indiana, its researchers are advancing human understanding through research, scholarship, education, and creative endeavor in order to be a repository for knowledge and a powerful means for doing good in the world. For more information, please visit NDR's website or NDR's LinkedIn.

Originally published by Erin Fennessy at gain.nd.edu on October 14, 2025.