From decades to years: Rising seas and cyclones amplify Bangladesh’s storm-tide hazards in a warming climate

Science for society

Bangladesh’s low-lying coast, home to 8 million people, is highly vulnerable to tropical cyclones and storm tides. The government has implemented proactive policies and preparedness programs to enhance the country’s resilience and protect against loss of life. However, under a warming climate the sea level will rise and tropical cyclones will intensify, likely elevating the risk of coastal flooding and overwhelming existing flood defenses. In the absence of observational data and powerful computational models, risk assessments adequate to inform infrastructure development are lacking.

Using a physics-based approach that accounts for changes in cyclone activity and sea-level rise, we present a storm-tide hazard risk assessment for Bangladesh under different warming scenarios and reveal an urgent need to update existing coastal defense strategies. Policymakers can use our assessments to enhance resilience, ensuring projects such as the Coastal Embankment Improvement Project and Multipurpose Disaster Shelter Project protect vulnerable communities.

Highlights

• TC climatology change and SLR worsen storm tides in Bangladesh in IPCC AR5 & AR6

• Storm-tide season widens, with peak intensification in late monsoon and post-monsoon

• Cyclone-monsoon cascades and sequential post-monsoon extremes deserve attention

• A joint sampling method integrates TC, SLR, and tides probabilistically in simulations

Summary

Rising sea levels and intensifying cyclones threaten Bangladesh’s low-lying, densely populated coast in a warming climate, putting millions at risk. Yet future risks remain poorly understood, limiting available guidance for climate adaptation. Here, we present a comprehensive storm-tide risk assessment for Bangladesh using a coupled statistical-physical downscaling and hydrodynamic framework that integrates projected cyclone activity and sea-level rise across multiple climate scenarios. Our scalable large-ensemble multimodel approach reveals a significant and previously unrecognized 10-fold drop in average late-century storm-tide return periods under middle- to high-emission pathways, with notable regional and seasonal variations. Two emerging risks require urgent attention: cascading cyclone-monsoon hazards in the late monsoon and sequential extremes in the post-monsoon. Our findings index storm-tide hazard estimates to climate scenarios to inform policymakers and planners on climate adaptation, infrastructure planning, and resilience strategies, and underscore the need to reassess ongoing coastal protection efforts.