Researchers Find Human-Caused Sea Level Rise Is Behind the Most Recent Increases in Extreme Water Levels

A study supported by a Rutgers-led consortium shows climate change is reshaping coastal flood risks worldwide

Rising seas are increasing the frequency of coastal flooding in many parts of the world, prompting researchers to better understand the role of human-caused climate change in those regions.

Until now, scientists have had limited ability to quantify how much climate change contributes to coastal flooding at local and regional scales. But a new study helps fill that gap by identifying the extent to which human-caused sea level rise is driving increases in extreme water levels around the globe.

"Sea level rise is making both tidal flooding and storm-driven flooding more frequent, extensive and expensive," said Robert Kopp, a Distinguished Professor in the Department of Earth and Planetary Sciences at the School of Environmental and Biological Sciences, the director of the Megalopolitan Coastal Transformation Hub (MACH) at Rutgers University and a coauthor of the study. "This work allows us to pinpoint the human role in driving these changes."

This work allows us to pinpoint the human role in driving these changes.

Robert Kopp

Distinguished Professor, Department of Earth and Planetary Sciences

The research, published in Science Advances and led by Climate Central, a nonprofit organization that conducts climate science research and public outreach, used two independent approaches to identify the role of climate change in rising sea levels. One estimated how much sea level rise resulted from warming oceans and melting land ice, both driven by human-caused warming. The other compared observed sea levels with a modeled version of the world in which climate-warming greenhouse gas pollution had never occurred.

Despite taking different approaches, both methods reached similar conclusions, providing evidence that human-caused sea level rise is responsible for much of the increase in extreme water levels observed throughout the world.

Scientists found that human-caused sea level rise is detectable at 97% of global tide gauge sites investigated and that climate change was responsible for 58% of the observed days with extreme water levels during 2000 to 2018. Averaged across all locations, climate change has nearly tripled the number of days exceeding extreme water level thresholds since the 1970s.

"This highlights how we've loaded the climate dice against not only our children and grandchildren, but ourselves," said Daniel Gilford, a climate scientist at Climate Central and an author of the study. "The effects of human-caused climate change are already here. We will continue to face growing threats like increasing coastal flood risks unless we immediately and sharply reduce our climate pollution."

Those findings are echoed by a complementary study published concurrently in Nature Climate Change by researchers at Tulane University. That study examined the contribution of human-caused sea level rise to changes in storm-driven coastal flooding.

Together, the two studies provide some of the clearest evidence to date that climate change is increasing coastal flood risks worldwide, Kopp said.

Both studies were co-supported by MACH, a National Science Foundation-funded, Rutgers-led consortium focused on advancing the science of coastal climate risk and helping communities adapt to rising seas and increasing flood hazards. Through partnerships among researchers, practitioners and community leaders, MACH works to improve understanding of coastal change and strengthen resilience across vulnerable regions.

Explore more of the ways Rutgers research is shaping the future.