South-east Asia reels as rare cluster of storms claims more than 800 lives

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Flooding across much of south-east Asia fuelled by a rare cluster of three tropical storms has claimed the lives of more than 800 people in five countries, with Indonesia the worst hit so far.

Meteorologists say the region’s most recent extreme weather appears to be driven by the interactions between Cyclone Senyar over the Malacca Strait and Typhoon Koto over the South China Sea. Cyclone Ditwah also formed over the Bay of Bengal towards the end of the week.

Exacerbating these weather patterns, meteorologists said, was the coincidence of two naturally occurring phenomena — La Niña in the Pacific Ocean and the Indian Ocean Dipole.

The La Niña cycle involves cooling across the central Pacific, which can then strengthen monsoon rains across south-east Asia. While the cycle is relatively weak this year, it has lingered.

At the same time, the western Indian Ocean Dipole is in its so-called negative cycle. This circulation pattern means sea-surface temperatures will be warmer than average in the eastern Indian Ocean, near Indonesia.

While these phenomena occur in separate basins with unique circulation patters, they can influence each other and create complex interactions.

In addition, sea surface temperatures in parts of the world have remained unusually warm this year. The rise in global average temperatures reached a record last year of more than 1.5C since the pre-industrial era, as a result of human-caused climate change. This is distinct from the 1.5C threshold set down in the Paris agreement, which is measured over two decades.

Oceans absorb about 90 per cent of the world’s excess heat trapped by greenhouse gases in the atmosphere, while warmer air holds more moisture.

Across south-east Asia, the incessant rains during the monsoon season have led to floods and landslides because of already saturated ground.

In Indonesia, rivers burst their banks on Sumatra, swept away villages and submerged tens of thousands of houses. Authorities said the death toll in the country by Saturday had risen to more than 400 and scores missing, AP reported. Almost 60,000 had been displaced.

Indonesia’s President Prabowo Subianto said many roads were cut off and survivors isolated, as rescue services were hampered by the conditions. “Even our helicopters and planes sometimes struggle to land,” he said.

In Thailand, the heaviest single rain event in what has been estimated to be three centuries was recorded. Severe flooding across nine southern provinces had killed at least 160 people and affected more than 3.2mn people, officials said.

A mass evacuation was ordered around the southern city of Hat Yai and a disaster zone was declared.

In neighbouring Malaysia, tens of thousands were displaced and rains were forecast to continue, with a severe weather alert remaining in force.

In Vietnam, weeks of heavy rainfall continued to batter the country, leading to at least 98 fatalities. Nearly 120,000 people have been displaced and more than 800,000 are thought to be affected.

In Sri Lanka, Cyclone Ditwah hit the central-eastern coast on Friday morning, bringing torrential rainfall and sustained wind speeds of 65km an hour. The government disaster-management centre estimated more than 190 people had died.

Richard Nugee, a retired lieutenant-general in the British Army and a national climate and security adviser, was among nine experts at a briefing in London this week to warn about the consequences of climate change.

“What concerns me most is not any single crisis. It’s crises cascading together,” he said. “Multiple crises, food, health, infrastructure, migration, energy, extreme weather . . . all hitting at the same time; eroding trust in government by slow or failed responses.”