Human-caused sea level rise drives 21st-century worldwide water level extremes

According to the press release, 58% of the extreme water level days observed at the study's tide gauges between 2000 and 2018 are attributable to human-caused sea level rise.¹ A human-caused signal in sea level shows up at 97% of the sites.¹ Averaged over all sites, the count of days above the extreme threshold has nearly tripled since the 1970s.^1,2

The paper appeared in Science Advances in June 2026.² Daniel M. Gilford of Climate Central is an author and Robert E. Kopp of Rutgers University a co-author.^1,2 It asks what share of the growth in extreme water level days, place by place and region by region, can be put down to human-caused climate change.¹ The press release says flood risk at the local and regional scale had not been studied this way before, leaving communities short of information.¹

The authors used two largely independent methods at 519 tide gauge sites, and both reach similar conclusions.¹ The first adds up the sea level rise attributable to four contributors:

• the ocean expanding as it warms
• mountain glaciers melting
• the Greenland ice sheet losing ice
• the Antarctic ice sheet losing ice¹

The second compares observed sea levels from 1900 to 2018 with a modelled version of the same period without climate-warming pollution.¹ This kind of modelled "what if" record is called a counterfactual.

A companion paper from Tulane University, "Human-driven sea-level rise has quadrupled the frequency of coastal sea-level extremes since 1900", came out at the same time in Nature Climate Change.¹ The Megalopolitan Coastal Transformation Hub (MACH) co-supported both studies. MACH is a consortium funded by the National Science Foundation and led by Rutgers.¹

The paper gives site-by-site attribution of extreme water level days at hundreds of tide gauges, data of the kind a coastal flood model draws on.¹ It also applies two attribution methods to the same question, one built from physical contributions and one from a counterfactual record.