Study: Warmer oceans fed intense rainfall, deadly floods in Asia
Ocean temperatures warmed by human-caused climate change fed the intense rainfall that triggered deadly floods and landslides across Asia in recent weeks, according to an analysis released Wednesday.
The rapid study by World Weather Attribution (WWA) focused on heavy rainfall from Cyclones “Senyar” and “Ditwah” in Malaysia, Thailand, Indonesia, and Sri Lanka starting late last month. The analysis found that warmer sea surface temperatures over the North Indian Ocean added energy to the cyclones.
Floods and landslides triggered by the storms have killed more than 1,600 people, with hundreds more still missing. The cyclones are the latest in a series of deadly weather disasters affecting Southeast Asia this year, resulting in loss of life and property damage.
“It rains a lot here but never like this. Usually, rain stops around September but this year it has been really bad. Every region of Sri Lanka has been affected, and our region has been the worst impacted,” said Shanmugavadivu Arunachalam, a 59-year-old schoolteacher in the mountain town of Hatton in Sri Lanka’s Central Province.
Heat and moisture
Sea surface temperatures over the North Indian Ocean were 0.2 degrees Celsius (0.3 degrees Fahrenheit) higher than the average over the past three decades, according to the WWA researchers.
Without global warming, the sea surface temperatures would have been about 1 degree Celsius (1.8 degrees Fahrenheit) colder than they were, according to the analysis. The warmer ocean temperatures provided heat and moisture to the storms.
When measuring overall temperatures, the world is currently 1.3 degrees Celsius (2.6 degrees Fahrenheit) warmer than global average during preindustrial times in the 19th century, according to the National Oceanic and Atmospheric Administration.
“When the atmosphere warms, it can hold more moisture. As a result, it rains more in a warmer atmosphere as compared to a world without climate change,” said Mariam Zachariah, with the Centre for Environmental Policy at Imperial College London and one of the report’s authors.
The WWA is a collection of researchers who use peer-reviewed methods to conduct rapid studies examining how extreme weather events are linked to climate change.
Planetary debt
The WWA often estimates how much worse climate change made a disaster using specific probabilities. In this case, though, the researchers said they could not estimate the precise contribution of climate change to the storms and ensuing heavy rains because of limitations in climate models for the affected islands.
Global warming is a “powerful amplifier” to the deadly floods, typhoons, and landslides that have ravaged Asia this year, said Jemilah Mahmood, with the Sunway Centre for Planetary Health, a Malaysia-based think tank that was not involved with the WWA analysis.
“The region and the world have been on this path because, for decades, economic development was prioritized over climate stability,” Mahmood said. “It’s created an accumulated planetary debt, and this has resulted in the crisis we face.”
The analysis found that across the affected countries, rapid urbanization, high population density, and infrastructure in low-lying flood plains have elevated exposure to flood events.
“The human toll from Cyclones Ditwah and Senyar is staggering,” said Maja Vahlberg, a technical adviser with the Red Cross Red Crescent Climate Centre. “Unfortunately, it is the most vulnerable people who experience the worst impacts and have the longest road to recovery.”
