Tropical cyclone climatology change greatly exacerbates US extreme rainfall-surge hazard

Changes to tropical cyclones will increase the risk to US coastlines. Under a high-emissions scenario, the joint hazards of extreme rainfall and storm tides increase, with the largest contribution being from increasing cyclone intensity and decreasing translation speed, rather than sea-level rise. Tropical cyclones (TCs) are drivers of extreme rainfall and surge, but the current and future TC rainfall-surge joint hazard has not been well quantified. Using a physics-based approach to simulate TC rainfall and storm tides, we show drastic increases in the joint hazard from historical to projected future (SSP5-8.5) conditions. The frequency of joint extreme events (exceeding both hazards' historical 100-year levels) may increase by 7-36-fold in the southern US and 30-195-fold in the Northeast by 2100. This increase in joint hazard is induced by sea-level rise and TC climatology change; the relative contribution of TC climatology change is higher than that of sea-level rise for 96% of the coast, largely due to rainfall increases. Increasing storm intensity and decreasing translation speed are the main TC change factors that cause higher rainfall and storm tides and up to 25% increase in their dependence.