Climate: Climate change may increase risk of successive hurricanes in the United States

Climate change could increase the likelihood of two tropical cyclones impacting the same coastal region within 15 days across the US Atlantic and Gulf coasts by the end of the century, according to a modelling study published in Nature Climate Change.

Tropical cyclones are one of the most devastating natural hazards for coastal areas, causing damage through strong winds, heavy rainfall and storm surges. How climate change affects these features of storms is complex. Most studies focus on the impact of climate change on single storms, while the risk of compound events — an event where two tropical cyclones impact the same location within a short time period — is not well understood. These events can be particularly damaging, as buildings and infrastructure will be more vulnerable to further damage, which also puts the lives of affected populations at risk.

Ning Lin and colleagues used climate models to assess how the frequency of successive tropical cyclone impacts (within 15 days of each other) changes along the US Atlantic and Gulf coasts under different emissions scenarios. Currently, successive hurricanes can affect coastal regions once in every 10 to 92 years, depending on the location. The authors find that under a moderate-emissions scenario (where CO2 emissions start to fall after 2050 but do not reach net zero by 2100), this average drops to 1 to 3 years, and under a high-emissions scenario (where CO2 emissions double by 2050), which is generally considered unlikely, it becomes 1 to 2 years by the end of the century. This change is linked to a higher tropical cyclone landfall frequency, as well as sea-level rise and increased storm intensity.

The authors note that there are uncertainties about the climate warming impact on the frequency and intensity of tropical cyclones, but conclude that their findings indicate that coastal resilience and infrastructure planning needs to consider an increased risk from sequential tropical cyclones during the twenty-first century.