Super-Typhoon Ragasa likely strengthened by human-driven climate change 

Contact Authors

• Davide Faranda, IPSL-CNRS, France  📨davide.faranda@lsce.ipsl.fr    🗣️English,French, Italian

• Tommaso Alberti, INGV, Italy  📨tommaso.alberti@ingv.it 🗣️ English, Italian

• Gianmarco Mengaldo, NUS, Singapore 📨mpegim@nus.edu.sg  🗣️Italian, English

Citation

Faranda, D., Alberti, T., & Mengaldo, G. (2025). Super-Typhoon Ragasa likely strengthened by human-driven climate change. ClimaMeter, Institut Pierre Simon Laplace, CNRS. https://doi.org/10.5281/zenodo.17201652

Press Summary

• Cyclones similar to Super Typhoon Ragasa are locally up to 10 mm/day (about 10%) wetter, around 1°C warmer, and roughly 4% windier today than in the past.

• Super Typhoon Ragasa's exceptional intensity and track make it a rare weather event with limited past analogues, and observed changes remain scattered.

• We mostly ascribe the heavier precipitation in Super Typhoon Ragasa to human driven climate change and natural climate variability likely played a modest role

Event Description

Between 21 and 23st of September 2025, Super Typhoon Ragasa underwent rapid intensification to Category 5 strength before lashing northern Luzon and eastern Taiwan with torrential rain, floods, and landslides. Across those three days, authorities reported rising casualties as floodwaters and landslides swept communities—at least 11 deaths in the Philippines and 14 in Taiwan by the 23rd, with search-and-rescue operations ongoing. Hong Kong came to a standstill on the 23rd as Signal No. 10 was issued, public transport was curtailed and hundreds of flights were disrupted while hurricane-force gusts and pounding seas battered the territory. Seawater surged into waterfront buildings—including hotel lobbies—while more than 90–100 injuries were recorded and thousands sought temporary shelter as emergency crews responded to widespread flooding. On China’s Guangdong coast, officials ordered mass evacuations exceeding two million people ahead of landfall near Yangjiang, where streets were submerged and more than 10,000 trees were destroyed. Power outages affected nearly half a million households across southern China as communications failed in parts of Jiangmen and schools and businesses were shut across Guangxi. Storm-surge warnings were raised along the Guangdong coastline, with waves forecast up to nearly 3 meters as Ragasa tracked west along the Pearl River Delta. By the evening of the 23rd, Ragasa had weakened while pushing along China’s south coast toward Vietnam, but cleanup was only beginning amid significant infrastructure damage and lingering flood risk.

The surface pressure anomalies show a strong negative anomaly, up to -10 hPa, centered over Luzon and the Philippine Sea. Temperature anomalies display a warm core with positive anomalies of +2°C to +3°C, surrounded by cooler regions inland. Precipitation data indicate extremely high daily totals, locally exceeding 150 mm/day along the Super Typhoon track and over mountainous terrain. Windspeed data reveal strong sustained winds up to 80 km/h directed toward the island, with the most intense gusts near the eyewall. Our analysis is based on ERA5 data, which assimilates some station observations, especially rainfall, but values may differ from those observed locally at weather stations.

Climate and Data Background for the Analysis

The Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) highlights that tropical Super Typhoons in the western North Pacific are expected to become more intense under climate change, even if their total number decreases. The report projects stronger storms, bringing heavier rainfall and higher storm surges, particularly affecting countries like the Philippines. Observations since the 1970s show that while the annual frequency of tropical Super Typhoons in the region has not significantly increased, the proportion of Category 4 and 5 storms has risen. Rainfall associated with typhoons has also become more extreme, with higher flood risks in both rural and urban areas. Projections for the 21st century indicate a likely reduction in the overall number of storms but a further increase in the share of the most intense Super Typhoons, alongside heavier rainfall linked to warmer sea surface temperatures.

Our approach looks for past weather situations similar to those of the current event. For Ragasa, we have medium-low confidence in the robustness of our approach, as strong historical Super Typhoons exist in the observational record, but the scale of this event remains at the upper edge of intensity for the area. Furthermore, our analysis showed sensitivity to the choice of the domain.

ClimaMeter Analysis 

We analyze here (see Methodology for more details) how events similar to the meteorological conditions leading to the  Super Typhoon Ragasa have changed in the present (1987–2023) compared to what they would have looked like if they had occurred in the past (1950–1986) in the region [111°E 128°E 13°N 25°N]. The Surface Pressure Changes show that Super Typhoons similar to Ragasa are up to 1 hPa shallower in the present climate. Temperature Changes show that present-day events are up to +1°C warmer in the Super Typhoon core compared to similar past storms. Precipitation Changes show wetter conditions, with up to +10 mm/day (around +10%) more rainfall along the Super Typhoon track. Windspeed Changes show slight increases of up to +4 km/h in coastal and offshore areas.

We also note that similar past events occur with comparable seasonality in both periods, mainly between July and September. Changes in urban areas reveal that Kaohsiung and Calayan experience significantly wetter conditions in the present than in the past, while Hong Kong shows a slight reduction in wind intensity and minor temperature changes.

Finally, we find that natural variability drivers, particularly the Atlantic Multidecadal Oscillation, may have partly modulated Ragasa’s trajectory and rainfall. However, the long-term changes in pressure, precipitation, and temperature strongly suggest that the event’s severity is largely consistent with human-driven climate change.

Conclusion

Based on the above, we conclude that Super Typhoons similar to Ragasa are around 1°C warmer, up to 10 mm/day (10%) wetter, and slightly windier by up to 4 km/h in the present compared to the past. They contribute to more extreme rainfall and flooding risks, particularly in the Philippines’ mountainous terrain and neighboring coastal regions. We interpret Super Typhoon Ragasa as an event of exceptional meteorological conditions whose characteristics can mostly be ascribed to human driven climate change.