Study Finds Extreme Coastal Flooding Now 12 Times More Likely Due to Rising Sea Levels

Research led by Sönke Dangendorf of Tulane University, published June 10 in Nature Climate Change, found that extreme coastal flooding events — defined as those with a 1-in-100-year historical probability — are now roughly 12 times more likely globally, with human-driven climate change responsible for approximately a fourfold increase since 1900. The study drew on long-term tide gauge records from more than 130 sites and climate model simulations to isolate the contributions of human activity, natural variability, and local land subsidence. At nearly half of the sites analyzed, what was once a 100-year flood now occurs at least once per decade; in Wellington, New Zealand, such an event now happens roughly twice per year, while in Manila, groundwater-driven land subsidence has amplified flood frequency more than 300-fold. The study's analysis runs through 2005, and the authors note their findings likely understate current risk given accelerating human contributions since then. A companion study published simultaneously in Science Advances found that climate change was responsible for approximately 58% of extreme flood days between 2000 and 2018, and has nearly tripled the number of days exceeding extreme flood thresholds since the 1970s. Although natural forces dominated sea-level changes earlier in the 20th century, human-caused warming has been the primary driver since the 1960s, with greenhouse gases from fossil fuel combustion identified as the dominant factor since the 1970s. Experts not involved in the research cautioned that existing coastal protections — including those in New Orleans — may be inadequate within the next few decades without sustained investment and forward-looking adaptation.