200,000kg of salt have been scattered in clouds in Indonesia © AFP/Getty Images
200,000kg of salt have been scattered in clouds in Indonesia © AFP/Getty Images

Can cloud seeding stop Indonesia's forest fires?

2 October 2019

Putting out one fire can be tricky. Putting out 1,374 fires, as the Indonesian government is trying to do, is harder still.

Yet the Environment and Forestry Ministry seems to be succeeding, although it’s hard to say how much of the progress is down to the fact that 317m litres of water have been dropped over blazing rainforest and how much is due to the 200,000kg of salt being scattered to seed clouds and make them rain.

Forest fires are an annual crisis in Indonesia, most prevalent in the dry season which stretches from March to June (or September in some parts of the country). Climate patterns – especially El Nino – are partly to blame but slash and burn agricultural practices don’t help. The government is trying to crack down – the rate of deforestation fell by 60% in 2017 – but the fires still choke the region most summers.

Indonesia’s rainmaking efforts are on a large scale but seem decidedly old school in comparison to the United Arab Emirates which is dispersing specially-designed “shell composite nano-material” to seed clouds. The UAE’s National Centre of Meteorology says that such operations accounted for 10-15% of rainfall in 2018. That proportion is expected to rise as tests suggest that the new nanomaterial would be much more effective than the previous method: salt crystals, coated with nanoparticles of titanium oxide.

Controlling the weather seems like the megalomaniacal behaviour we would expect from a James Bond villain but for some governments, making rain could well be a question of survival. The World Resources Index estimates that 17 countries, home to a quarter of the world’s population, face what it calls “extremely high water stress”. That partly explains why at least 56 countries are now said to be investing in schemes to manipulate weather.

Making rain is one of homo sapiens’ longest held ambitions. In ancient India, mantras and offerings were made to encourage precipitation. In Europe in the Dark Ages, the superstition that Finnish people could control the weather was so prevalent that the Vikings, no wimps by any standards of masculinity, refused to allow them on their ships.

In the 1890s, testing a theory that battles ­– and shooting – provoked rain, American General Robert Dyrenforth fired $9,000 of gunpowder and high-explosives on a range in Texas. After a few barrels, it did rain a bit, but locals insisted that it would probably have rained anyway. The general acquired the nickname ‘Dry-Henceforth’. The difficulty of proving the efficacy of their experiments with hard data has bedevilled rain makers ever since.

The modern history of weather manipulation begins in the autumn of 1946 when keen mountaineer Vincent Schaefer sprinkled 1.4kg of finely ground dry ice on a watery, stratus cloud above Mount Washington, New Hampshire. Within five minutes, so many snowflakes were falling from the cloud that a hole opened up in it. The press hailed the experiment as conclusive proof that, as Schaefer’s collaborator, the Nobel Prize-winning chemist Irving Langmuir had argued, we could manipulate the weather.

In the 1950s, joint experiments by the US military, the Weather Bureau and private companies were so promising that, at one point, almost one-tenth of American land was being cloud-seeded. Unfortunately, as professional weather watcher Paul Simon has noted: “The bubble eventually burst when the results of seeding failed to meet its promises. Precipitation was often slight and unpredictable.” Some of the apparently impressive claims for cloud-seeding, he concluded, “still fall within the range of natural weather variations”.

Such doubts won’t stop governments from trying. Optimists take encouragement from a 2018 experiment in Idaho in which cloud seeders produced snowflakes that were 8mm in diameter – heavy enough to fall to the ground. Pessimists question the cost effectiveness. You can’t seed any old cloud – they have to be supercooled – and some scientists argue that the best results will happen around the poles in winter, where cirrus clouds form primarily without dust particles. Other experts, including those in the American military, say cloud-seeding is most effective in areas which already have heavy rain. As no two weather conditions are the same, replicating success is also something of a challenge.

There is also a fear that weather could be weaponised. The Pentagon tried to do so in Vietnam with Operation Popeye. Between 1967 and 1972, five US aircraft flew two sorties a day during the rainy season, to seed clouds above parts of the Ho Chi Minh trail, used to ship supplies and personnel between North Vietnam and the Vietcong guerrillas. The mission’s slogan was “Make mud, not war” and, although the US Defence Intelligence Agency claimed a 30% increase in rainfall, officers admit the effectiveness of the operation could not be “precisely quantified”.  (Such efforts are now illegal under international law.)

Some experts question whether rain making is the best way to combat water shortages. In the Middle East and North Africa, where water is especially precious, 82% of wastewater is not re-used. In India, which government researchers say is suffering “the worst water crisis in the country’s history”, a new ministry has been set up to coordinate a new water strategy which could involve better irrigation, conserving and restoring lakes, and the collection and storage of rainwater.

There are also those who argue that governments and companies should not ‘play God’ and try to manipulate the world’s climate. Ultimately, it comes down, as American scientist Alan Robock suggested in his 2016 study, to how we assess risk and reward. If climate change reaches crisis point, it may make sense to send planes, ships and drones to seed clouds across the planet to reduce the surface temperature and, in theory, help halt, or reverse, the impact of global warming. That process will have unexpected consequences but, with the planet in such peril, Robock suggests it would be worth the risk.

Until then, Robock argues the business of seeding clouds is something we should seriously study because, if it ever is going to save the planet, we need to become much better at it. From that point of view, Indonesia’s efforts – only 136 of the original 1,347 fires are still burning – could be significant not just for its rainforests but for the whole of the world.

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