Human-driven sea-level rise has increased frequency of extreme coastal flooding, study says

A study released Wednesday in *Nature Climate Change* revealed that extreme coastal flooding events, once rare with a 1% annual probability, now occur on average 12 times more frequently worldwide. The research attributed fourfold of this increase to human-driven climate change, using tide gauge records from over 100 locations spanning 1900 to 2005. While natural forces dominated earlier in the 20th century, human-caused warming became the primary factor behind rising sea levels after the 1960s, according to the study’s lead author, Sönke Dangendorf, an associate professor at Tulane University. The findings highlight the growing threat to coastal communities, where flooding endangers hundreds of millions of people and causes billions in damages annually. Hurricane Ian in 2022 exemplified how climate change intensifies such events, with scientists confirming its strength was amplified by global heating. The study’s authors noted their results were conservative, as human contributions to coastal extremes have risen further since 2005. A complementary study in *Science Advances* reinforced these conclusions, identifying climate change as the root cause for 58% of extreme water-level days between 2000 and 2018. It also found that the number of days exceeding extreme thresholds has nearly tripled since the 1970s. Ben Strauss, chief scientist at Climate Central and a co-author, stated that nearly every coastal flood today bears the ‘fingerprints’ of human-induced sea-level rise, emphasizing that without climate change, many would not qualify as floods. The research underscored the urgent need for adaptation, as current protections—such as those in New Orleans—may become inadequate within decades. Jeff Williams, a retired US Geological Survey oceanographer, warned planners to account for rising risks and address the financial burden of coastal defenses. Dangendorf stressed that greenhouse gas emissions from fossil fuels remain the dominant factor, demanding immediate action to mitigate future risks. While global renewable energy adoption has surged—clean power generation surpassed overall electricity demand growth last year—the studies serve as a stark reminder of the consequences of inaction. The findings call for stronger coastal infrastructure planning and global efforts to curb emissions to prevent worsening extremes.