The climate service of the European Earth observation program Copernicus now offers a comprehensive dataset that documents changes in water storage worldwide. The data show how much the current volume of water in a region—in soils, groundwater, lakes, rivers, snow, and ice—deviates from the long-term average.

The University of Bern plays a central role in this effort: Researchers at the Astronomical Institute (AIUB) are providing key calculations for the dataset, which is now continuously updated and freely accessible via the Climate Data Store of the Copernicus Climate Change Service (C3S) (see info box).

Adrian Jäggi, co-director of the AIUB, explains: “The dataset is of great importance to anyone who needs to know where water is disappearing or increasing over the long term on a large scale across the Earth—for example, for weather and climate services, for decision-makers in politics and administration, for insurance companies and NGOs, as well as for climate research and hydrology.”

Satellites Measure Water Shifts

The Earth has an uneven gravitational field, meaning the force of gravity varies from place to place. This gravitational field changes when large volumes of water shift. Special satellite missions such as GRACE and GRACE-FO can measure these minute changes in gravity.

Jäggi says: “At the University of Bern, these measurements are used to create global gravity field models that show where water is decreasing or increasing on a large scale. To ensure these models are as robust and accurate as possible, the Astronomical Institute operates a combination center that integrates the models—based on slightly different approaches—from all international research groups in this field into a final model. This makes it possible to create maps that depict changes in water storage even more accurately compared to a long-term average.”

Significance for Climate Monitoring and Society

Water is essential for life, and climate change is significantly affecting the global water cycle: Droughts are becoming more frequent or more intense, glaciers are melting , and heavy precipitation and flooding are on the rise. To understand these changes and adapt to them, reliable and long-term comparable data are needed.

Jäggi says: “The new dataset helps identify regions that are losing water and supports policymakers and the private sector in planning irrigation and infrastructure. The data is therefore also of great importance for global climate monitoring.”

With the new Copernicus dataset, the University of Bern’s research findings are being integrated into a permanent European climate service. This improves the accessibility and reliability of the data for users worldwide. “The University of Bern is thus contributing directly to the Copernicus Earth observation program. It is doing so free of charge, as the work of Bern researchers on Copernicus will no longer be funded starting in 2023 because Switzerland is not participating in Copernicus,” says Jäggi.

The University of Bern is also involved in developing the data processing system for the next ESA gravity mission, scheduled to launch in 2032. Similar to GRACE/GRACE-FO, it will measure minute changes in Earth’s gravitational field, thereby providing an even more precise picture of how water and ice are changing on Earth. This will make it easier to detect changes in individual river basins, mountainous regions, or groundwater reservoirs and to determine long-term climate trends with greater certainty. “The goal is to establish a continuous, decades-long data series on changes in water and ice masses—as a solid foundation for climate research and climate policy,” says Jäggi. “In this way, the University of Bern is actively shaping the future of climate research and contributing to the monitoring of global water storage,” Jäggi concludes.