The Impact of the El Niño-Southern Oscillation on Tropical Cyclone Socio-Economic Risks

Abstract

The El Niño-Southern Oscillation (ENSO) is the most important inter-annual signal of climate variability on the planet. It affects many natural hazards, including tropical cyclones (TCs), which are known for causing severe economic losses and many fatalities. However, although research efforts have examined ENSO’s influence on TC characteristics in different basins, the transfer from findings on ENSO’s impact on TC hazard into global TC risk assessments has yet to been undertaken. To address this, in this thesis we assess TC risks on physical assets under ENSO’s influence on a global scale using the International Best Track Archive for Climate Stewardship (IBTrACS), based on the risk assessment platform CLIMADA. Based on successful replication of existing state-of-the-art findings on TC characteristics (frequency and intensity) during historical ENSO events across ocean basins, we found differences in anomalies of TC risks relative to all years in El Niño years and La Niña years in the North Atlantic and Eastern Pacific basins. We observe higher-than-average 10- year impact on physical assets in La Niña years, and lower-than-average in El Niño years in the North Atlantic basin, while a reversed situation shows in the Eastern Pacific basin. Mexico experiences higher TC damages in the east coast in La Niña years, and in the west coast in El Niño years, while the United States experience higher (lower) TC damage in La Niña (El Niño) years. Furthermore, we quantify the uncertainties of TC landfall locations using probabilistic TC tracks generated by a random walk algorithm, and find the noise of random tracks dominates in basins and regions with scarce TC data. Our results show the potential of including climate variability such as ENSO into TC risk analysis. The quantification of TC risk anomalies in El Niño and La Niña years not only provide a valuable foundation of seasonal TC risk prediction for both policy makers and insurance industry, but also for the establishment of more balanced and diversified multi-hazard risk portfolios.