This post was originally published on here
Droughts and floods can disrupt daily life, damage ecosystems, and strain local and global economies. Scientists at The University of Texas at Austin set out to better understand these water extremes by studying how they develop and spread across the planet. Their work points to a powerful climate force that links distant regions in surprising ways.
A new study published in AGU Advances shows that during the past 20 years, ENSO, a recurring climate pattern in the equatorial Pacific Ocean that includes El Niño and La Niña, has played the leading role in driving extreme changes in total water storage worldwide. The researchers also found that ENSO tends to line up these extremes so that different continents experience unusually wet or dry conditions at the same time.
Why Synchronized Extremes Matter
According to study co-author Bridget Scanlon, a research professor at the Bureau of Economic Geology at the UT Jackson School of Geosciences, understanding these global patterns has real-world consequences.
“Looking at the global scale, we can identify what areas are simultaneously wet or simultaneously dry,” Scanlon said. “And that of course affects water availability, food production, food trade — all of these global things.”
When multiple regions face water shortages or excesses at once, the impacts can ripple through agriculture, trade, and humanitarian planning.
Measuring All the Water on Earth
Total water storage is a key climate indicator because it accounts for all forms of water in a region. This includes rivers and lakes, snow and ice, moisture in the soil, and groundwater below the surface. By focusing on this full picture, researchers can better understand how water moves and changes over time.
The study is one of the first to examine total water storage extremes alongside ENSO (The El Niño-Southern Oscillation) on a global scale. This approach made it possible to see how extreme wet and dry conditions are connected across large distances, said lead author Ashraf Rateb, a research assistant professor at the bureau.
“Most studies count extreme events or measure how severe they are, but by definition extremes are rare. That gives you very few data points to study changes over time,” Rateb said. “Instead, we examined how extremes are spatially connected, which provides much more information about the patterns driving droughts and floods globally.”
Satellites Reveal Hidden Water Changes
To estimate total water storage, the scientists relied on gravity measurements from NASA’s GRACE and GRACE Follow-On (GRACE-FO) satellites. These data allow researchers to detect changes in water mass over areas about 300 to 400 kilometers wide, roughly the size of Indiana.
The team classified wet extremes as water storage levels above the 90th percentile for a given region. Dry extremes were defined as levels below the 10th percentile.
Their analysis showed that unusual ENSO activity can push widely separated parts of the world into extreme conditions at the same time. In some regions, El Niño is linked to dry extremes, while in others the same dry conditions are associated with La Niña. Wet extremes tend to follow the opposite pattern.
Real-World Examples Across Continents
The researchers pointed to several striking cases. During the mid-2000s, El Niño coincided with severe dryness in South Africa. Another El Niño event was linked to drought in the Amazon during 2015-2016. By contrast, La Niña in 2010-2011 brought exceptionally wet conditions to Australia, southeast Brazil, and South Africa.
Beyond individual events, the study also identified a broader shift in global water behavior around 2011-2012. Before 2011, unusually wet conditions were more common worldwide. After 2012, dry extremes began to dominate. The researchers attribute this change to a long-lasting climate pattern in the Pacific Ocean that influences how ENSO affects global water.
Filling the Gaps in Satellite Records
Because GRACE and GRACE-FO data are not continuous, including an 11-month gap between missions in 2017-2018, the team used probabilistic models based on spatial patterns to reconstruct missing periods of total water storage extremes.
Although the satellite record covers only 22 years (2002-2024), it still reveals how closely climate and water systems are linked across the Earth, said JT Reager, deputy project scientist for the GRACE-FO mission at NASA’s Jet Propulsion Laboratory and JPL Discipline Program manager for the Water and Energy Cycle.
“They’re really capturing the rhythm of these big climate cycles like El Niño and La Niña and how they affect floods and droughts, which are something we all experience,” said Reager, who was not involved in the study. “It’s not just the Pacific Ocean out there doing its own thing. Everything that happens out there seems to end up affecting us all here on land.”
Preparing for Extremes, Not Just Shortages
Scanlon said the findings underscore the need to rethink how society talks about water challenges. Instead of focusing only on scarcity, she said, it is critical to plan for swings between too much and too little water.
“Oftentimes we hear the mantra that we’re running out of water, but really it’s managing extremes,” Scanlon said. “And that’s quite a different message.”
The research was funded by the UT Jackson School of Geosciences.
