Ocean warmed by climate change fed rainfall, deadly floods in Asia: Study

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 on Wednesday.

The rapid study by World Weather Attribution 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.

Warmer sea surface temperatures  Sea surface temperatures over the North Indian Ocean were 0.2 degrees Celsius 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 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 warmer than global average during pre-industrial 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.

Using tested methods to measure climate impacts quickly  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.

"Anytime we decide to do a study, we know what is the procedure that we have to follow," said Zachariah, who added that they review the findings in house and send some of their analysis for peer review, even after an early version is made public.

The speed at which the WWA releases their analysis helps inform the general public about the impacts of climate change, according to Zachariah.

"We want people everywhere to know about why something happened in their neighbourhood," Zachariah said. "But also be aware about the reasons behind some of the events unfurling across the world."  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.

Climate change boosts Asia's unusually heavy rainfall  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 prioritised 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 urbanisation, 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.