The influence of anthropogenic climate change on Super Typhoon Odette (Typhoon Rai) and its impacts in the Philippines

Abstract. Super Typhoon Odette (Typhoon Rai) made landfall in the Philippines as a category 5 tropical cyclone on 16^th December 2021. It brought the compounding effects of extreme rainfall, high winds and storm surge to large parts of the southern-central Philippines, particularly Cebu and Bohol. It was the second costliest typhoon on record for the Philippines up until 2021, causing nearly a billion dollars (US) in direct damage and widespread disruption. In this study, the extreme rainfall and high winds observed during this storm are assessed to determine the influence of anthropogenic climate change (ACC), using three different methods, which focus on the circulation patterns, high rainfall and strong winds associated with Odette, respectively. First, we check that the current generation of higher resolution models used in attribution studies can capture the low sea level pressure anomaly associated with Typhoon Odette and hence can be used to study this type of event. A short analysis then compares such circulation analogues and the associated meteorological extremes over three time periods: past (1950–1970), present (2001–2021), and future (2030–2050), finding evidence of an increase in large-scale precipitation between past and present periods. Second, a multi-method multi-model probabilistic event attribution finds that extreme daily rainfall such as that observed during Typhoon Odette has become about 2 (0.1 to 290) times as likely during the Typhoon season over the southern-central Philippines due to ACC. Third, a large ensemble tropical cyclone hazard model finds that the wind speeds of category 5 landfalling typhoons like Odette have become approximately 70 % (3 to 200 %) more likely due to ACC. The combined results show that both extreme rainfall and wind speeds in the Philippines due to storms like Odette have become significantly more likely and intense due to ACC, albeit with wide uncertainties on precipitation. Based on these results and compound event attribution theory, we further conclude that ACC has likely more than doubled the likelihood of a compound event like Typhoon Odette and played a key role in amplifying the damages from the event.