What are cloudbursts and why climate change may make them more destructive

Sudden and intense downpours known as cloudbursts are triggering deadly floods and landslides across South Asia, with scientists warning that a warming climate is likely to make them more frequent and severe.

In northwest Pakistan, flash floods killed at least 321 people in 48 hours last week, local officials said. "Entire villages have been wiped out. People are still trapped under thick mud and debris," said Abdul Nasir Khan, a senior disaster management official in Khyber Pakhtunkhwa province, reports CNN.

In India-administered Kashmir, at least 60 people died and more than 200 were missing when torrents of mud and water swept through the Himalayan town of Chashoti. "We watched the flood swallow houses within minutes. It was like the mountains themselves were falling," said resident Bashir Ahmed.

Authorities in both countries said much of the devastation was caused by cloudbursts — violent bursts of rain that can overwhelm mountain valleys and destroy entire communities.

What are cloudbursts?

The India Meteorological Department defines a cloudburst as rainfall exceeding 100 mm an hour over a small area. They strike most often in the summer monsoon, when moisture-heavy winds from the Indian Ocean collide with steep mountain ranges.

"The Himalayas, Karakoram and Hindu Kush are especially vulnerable because of their steep slopes, fragile geology and narrow valleys that funnel storm runoff into destructive torrents," said Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology.

In Pakistan's hard-hit Salarzai, residents said a wall of water and mud carried massive boulders through the valley. "The ground shook like an earthquake. We had no time to run," said villager Rahmatullah Khan.

Why are they so destructive?

Cloudbursts are notoriously hard to forecast. "The storms are too small and fast for precise prediction," said Koll. "This is also a data-sparse region, which makes it harder to understand, monitor and forecast these events."

Poor communications and infrastructure leave communities more exposed. "The bigger gap is not the technology gap, it's the communication gap," said Islamabad-based climate expert Ali Tauqeer Sheikh. "People living in hazard zones often don't get warnings in time."

Sheikh said deforestation and unplanned development amplify the impacts. "Because of heavy deforestation, any torrential rain will result in landslides and mudslides. They'll bring boulders and timber with them," he said.

"There are often heavy casualties because so many people live along rivers and streams, and the preparedness time is extremely limited," he added.

Role of climate change

Scientists say global warming is intensifying rainfall extremes. "Warmer oceans are loading the monsoon with extra moisture, and a warmer atmosphere holds more water, fueling intense rainfall when moist air is forced up steep mountain slopes," Koll said.

Sheikh noted that South Asia's searing heatwaves also contribute. "For each degree above average temperature, there's about 7% more moisture in the air. Stronger heatwaves in India or Pakistan mean heavier rainfall."

Glacial melt is worsening risks by destabilising lakes and terrain. "While glacial melt does not directly cause cloudbursts, it creates unstable lakes and fragile terrain that can worsen their impacts," said Koll.

Pakistan, which produces less than 1% of global emissions, has already suffered repeated climate shocks. "Average rainfall seems to have decreased in Pakistan, but the frequency of torrential rains has increased," Sheikh said. "We now see drought and flooding within the same month."

Regional cooperation

Experts say shared threats demand cross-border solutions. "It is super critical for the governments of South Asian nations to come together," Sheikh said. "We face the same set of problems, and there are similar solutions. But our ability to learn from each other is handicapped."

That cooperation has been undermined by political tensions. India suspended part of the Indus Water Treaty with Pakistan earlier this year after renewed clashes in Kashmir. "The Indus Water Treaty needs another lease of life to tackle emerging climate threats," Sheikh said.

Resilience measures, scientists say, include restricting settlements in hazard zones, enforcing climate-resilient infrastructure and strengthening early warning systems. "Avoiding construction in high-risk areas and improving early warnings are essential," Koll said.