El Nino fires test limits of Southeast Asia’s cloud-seeding bet

Cloud-seeding missions in the skies above Southeast Asia have done little to snuff out wildfires or disperse the haze that’s cloaked the region for months, exposing the limitations of attempts to modify the weather.

Between them, Indonesia and Malaysia have conducted more than 100 operations this year in an attempt to engineer rain to combat extreme dryness — exacerbated by El Nino — that has parched soils across the islands of Sumatra and Borneo. Toxic smog from the worst wildfire season in a decade has disrupted oil palm harvests, forced schools to close and reduced air quality to unhealthy levels in neighboring Singapore and Kuala Lumpur.

But the costly missions — which even included the use of dry ice to break up areas of warm air that trap smog near the ground — have so far brought little in the way of lasting results. As countries spend more trying to alter increasingly erratic rainfall patterns, that raises questions about the payoff for such investments when weather is at its extremes.

“Sometimes, there’s a lot of political pressure to do things that may not be really well-founded scientifically,” said Steven Siems, a professor at Monash University in Melbourne, Australia, and co-chair of an expert team on weather modification at the World Meteorological Organization.

Worldwide, demand for cloud-seeding technology has grown in recent years as the weather becomes more volatile, according to the WMO. That includes Southeast Asia, where the technique is used primarily to replenish reservoirs and aid crop development, as well as for dispersing smog during the annual wildfire season.

But tropical regions face additional challenges. Nearer the equator, cloud formations change more rapidly than in cooler mid-latitude regions, where more established research exists to quantify increases in precipitation as a result of seeding.

“There’s just so much natural variability” in the rain-bearing clouds being targeted in Malaysia and Indonesia, Siems said. In the tropics, specifically, the “full sequence of science” — from seeding to higher precipitation — “hasn’t really been demonstrated for the wider scientific community,” he added.

This year, rain has been particularly scarce across swaths of Southeast Asia. Against a 30-year average, Indonesia received just a fifth and Malaysia a third of normal levels from June through Oct. 25, data from weather analytics firm Atmospheric G2 showed. In such abnormally dry conditions, the effectiveness of cloud seeding is naturally limited.

“As the name suggests, cloud seeding requires clouds in the first place,” said Budi Harsoyo, director of weather-modification operations at Indonesia’s Meteorology, Climatology and Geophysics Agency. “When atmospheric conditions are dry, suitable clouds, such as cumulus clouds, are very difficult to find.”

Harsoyo didn’t provide a quantitative estimate of how much rainfall this year’s interventions might have generated. To assess its missions, he said, the agency compares flight paths and seeding locations with radar and satellite data to determine whether rainfall may have been influenced by the cloud seeding.

Less conventionally, Indonesia has also trialed the use of dry ice to free haze trapped near the ground. Unlike cloud seeding, the technique is aimed at rapidly cooling the surrounding air, weakening temperature inversions and allowing the smog to disperse.

After the first trial flight over South Sumatra province this month, the agency reported localized improvements in visibility and a decline in the concentration of fine-particle air pollution. However, it added that further evaluation was needed to determine how much of the improvement was attributable to dry ice rather than other atmospheric factors.

In the meantime, both countries are pressing on with their cloud-seeding efforts. As of Oct. 23, Indonesia had conducted 56 operations this year, involving 777 flights. That’s nearly triple the number of flights last year and more than seven times the total for 2024, according to data from the weather agency. The expansion comes despite limited cloud formations as a result of the dry atmospheric conditions.

Flying such missions isn’t cheap: in Indonesia, they cost the agency between 200 million and 300 million rupiah ($11,100 to $16,600) a day, assuming around two hours of flying time, Harsoyo said. Private operators generally charge up to 40% more to cover taxes, salaries and other costs.

In Malaysia, a single cloud-seeding operation costs, on average, some 100,000 ringgit ($24,500), local newspaper The Star quoted Natural Resources and Environmental Sustainability Minister Arthur Joseph Kurup as saying earlier this month. The country has carried out 65 operations so far this year, the most in a decade, according to data from MetMalaysia, the national weather agency.

They’re conducted “not only for the haze, but also to increase water levels and for dams,” said Ambun Dindang, MetMalaysia’s deputy director general for operations. Each mission is assessed by observing the growth of a cloud on radar, he added, as well as by pilots who fly into recently seeded clouds to observe additional moisture on the cockpit windshield.

Of course, weather-modification techniques are just one way that Indonesian authorities are attempting to put out the wildfires. In addition, the country has deployed firefighters at ground level and conducted water bombing from the air.

“The top priority is still to extinguish the fires at their source,” Harsoyo said. “Wildfires can’t be tackled through a single intervention alone.”