Increasing heavy rainfall and extreme flood heights in a warming climate threaten densely populated regions across Sri Lanka and the Malacca Strait

A World Weather Attribution study examines the role of climate change and natural variability in the devastating floods of November 2025 across Sri Lanka and the Malacca Strait. While observational data indicate a significant increase in the intensity of extreme 5-day rainfall events—up to 160% in Sri Lanka and 50% in the Malacca Strait due to a 1.3°C rise in global temperatures—climate models failed to consistently capture these trends, preventing a definitive quantitative attribution. The study also notes that La Niña and a negative Indian Ocean Dipole contributed between 5% and 13% to the rainfall in the Malacca Strait, while rapid urbanization and infrastructure failures exacerbated the humanitarian impact.

• Observational data suggest that extreme rainfall events have become more intense due to the 1.3°C rise in global mean surface temperature (GMST). In the Malacca Strait region, the increase is estimated between 9% and 50%, while in Sri Lanka, heavy 5-day precipitation events are now approximately 28% to 160% more intense.
• Natural climate variability patterns, specifically La Niña and a negative Indian Ocean Dipole (IOD), enhanced the intensity of rainfall in the Malacca Strait, contributing an estimated 5% to 13% to the observed rainfall.
• A definitive quantitative attribution of the events to human-driven climate change was not possible because high-resolution climate models did not show consistent results regarding the direction of change and failed to capture the trends visible in observations.
• The humanitarian impact was worsened by socio-economic factors, including rapid urbanization in flood-prone areas and the disproportionate effect of cascading infrastructure failures on low-income and marginalized groups.
• Sea surface temperatures (SSTs) in the North Indian Ocean were approximately 0.2°C above the 1991-2020 average, increasing the energy available for evaporation and tropical storm development; without the 1.3°C global warming trend, these SSTs would have been about one degree colder.

APA

World Weather Attribution (2025). Increasing heavy rainfall and extreme flood heights in a warming climate threaten densely populated regions across Sri Lanka and the Malacca Strait. https://www.worldweatherattribution.org/increasing-heavy-rainfall-and-extreme-flood-heights-in-a-warming-climate-threaten-densely-populated-regions-across-sri-lanka-and-the-malacca-strait/

Chicago

World Weather Attribution. Increasing heavy rainfall and extreme flood heights in a warming climate threaten densely populated regions across Sri Lanka and the Malacca Strait. 2025. https://www.worldweatherattribution.org/increasing-heavy-rainfall-and-extreme-flood-heights-in-a-warming-climate-threaten-densely-populated-regions-across-sri-lanka-and-the-malacca-strait/.

Wikipedia

{{cite report |author=World Weather Attribution |title=Increasing heavy rainfall and extreme flood heights in a warming climate threaten densely populated regions across Sri Lanka and the Malacca Strait |date=10 December 2025 |url=https://www.worldweatherattribution.org/increasing-heavy-rainfall-and-extreme-flood-heights-in-a-warming-climate-threaten-densely-populated-regions-across-sri-lanka-and-the-malacca-strait/ |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{worldweatherattribution2025increasing, author = {{World Weather Attribution}}, title = {{Increasing heavy rainfall and extreme flood heights in a warming climate threaten densely populated regions across Sri Lanka and the Malacca Strait}}, institution = {World Weather Attribution}, year = {2025}, month = dec, url = {https://www.worldweatherattribution.org/increasing-heavy-rainfall-and-extreme-flood-heights-in-a-warming-climate-threaten-densely-populated-regions-across-sri-lanka-and-the-malacca-strait/}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }