A new study by Imperial College reveals that climate change has significantly increased both the intensity and economic damage potential of Typhoon “Ragasa,” providing a clear example of how global warming is exacerbating tropical cyclone hazards. Using advanced climate models and satellite data, researchers quantified the human influence on extreme rainfall and wind-driven destruction.
The study employed the metric of Fractional Attributable Risk (FAR) to estimate how much climate change has contributed to the probability of Ragasa-type events. FAR is calculated as the difference between the probability of an event occurring in today’s climate versus the pre-industrial climate, divided by the probability in today’s climate. For Ragasa, the FAR was determined to be 0.49, indicating that nearly half of the likelihood of such a storm can be attributed to climate change.
The researchers also analyzed the typhoon’s maximum eyewall rainfall, recorded at 17.1 mm per hour at landfall. The frequency of such intense rainfall events has risen sharply: the return period has dropped from 8.8 years in pre-industrial conditions to 6.7 years today, a 33% increase. The maximum rain rate itself has increased by 1.9 mm/h (13%) due to climate change, with a FAR of 0.25 for rainfall specifically. Projections for a +2°C warmer world indicate that Ragasa-type storms could become even more frequent, with a return period of 5.5 years and rainfall rates increasing by 3.7 mm/h, a 22% rise from pre-industrial levels.
Beyond meteorological impacts, the study assessed economic damages using the IRIS model, combining wind fields with a damage function calibrated for population growth and inflation. Wind speed increases alone have already intensified damage potential. To communicate climate change’s effect on losses, researchers introduced a new measure: Fractional Attributable Loss (FAL), which compares economic loss in today’s climate to a pre-industrial baseline.
For Ragasa, FAL is 0.36, meaning 36% of the storm’s median economic damage can be attributed to climate change. Sensitivity tests show this estimate is robust, ranging from 31% to 39%, even across a wide spectrum of possible losses. In a +2°C scenario, damages could rise by an additional 27%, nearly doubling compared to pre-industrial conditions.
These findings highlight the escalating economic and humanitarian costs of tropical cyclones in a warming world. As climate change continues to intensify storms like Ragasa, understanding both the meteorological and economic implications becomes crucial for policymakers, urban planners, and disaster response agencies. Coastal populations and infrastructure are increasingly vulnerable, emphasizing the urgent need for emission reductions and climate-resilient planning.
The study also provides visual data through return period curves and damage projections, clearly illustrating how even small increases in storm intensity due to climate change can lead to disproportionately higher economic losses, particularly in densely populated regions such as South China and Hong Kong.
This research underscores the tangible impacts of climate change on extreme weather events and the importance of integrating climate attribution into disaster risk management and economic planning.