Cloud seeding program suspended over Snowy Hydro

The following year, the CSIRO began flying dry ice and silver iodide into the clouds using Air Force jets to test whether they could trigger rain.

In the decades that followed, some results were promising – CSIRO scientists reported 30 percent more rainfall in cloud-covered areas over Tasmania – but many of the experiments were inconclusive and the method remained controversial.

Part of the problem was that when conducting experiments in such a variable natural environment, it was extremely difficult to determine whether cloud seeding resulted in more rain and snowfall.

But over the past decade, advancing research has confirmed that cloud seeding can produce 5 to 30 percent more snow and can even produce precipitation where none would otherwise have fallen, says Professor Steve Siems, a cloud seeding expert at Monash University.

How does cloud seeding work?

Cloud seeding cannot conjure up a rain cloud out of thin air, but it can help trigger rain or extract snowfall from an existing cloud that might not have otherwise produced precipitation.

The technique used by Snowy Hydro is called glaciogenic seeding. When water levels in clouds are below freezing but have not yet formed ice, the silver iodide particles act as ‘ice nuclei’, providing a structure on which ice crystals can grow.

Once the ice crystals are large and heavy enough, they fall as rain or snow. This only works under certain conditions, but the two locations in Australia where cloud seeding has been deployed – via Snowy Hydro and Hydro Tasmania – offer some of the best conditions in the world for cloud seeding, according to Siems.

“We get very, very clean air from the Southern Ocean. We don’t have a lot of dust or pollution in the air. We get some of the cleanest air in the world from the Southern Ocean, so there are no ice cores there.”

While aircraft distributed the vaccine in Tasmania, Snowy Hydro sprayed tiny amounts of silver iodide over a propane flame on the ground to raise the particles into suitable clouds.

Controversies and conspiracies

Although research over the past decade has shown that cloud seeding can produce precipitation, there is widespread public skepticism about the practice and it is a popular bogeyman for conspiracy theorists.

This practice came under fire in 2016 when it was revealed that Hydro Tasmania had carried out cloud seeding the day before the deadly floods. An independent investigation found that the seedings had no effect on the extreme weather that caused the floods. However, the reputational damage was done and Hydro Tasmania suspended its seeding program.

Siems has been involved in numerous efforts by news organizations to debunk myths and show that various natural storm disasters, from Dubai to Lismore, are not the deliberate doing of a government cloud-seeding. “I think that’s part of the world we live in today, with QAnon and misinformation,” he said.

More valid concerns relate to the environmental impacts of silver iodine and the disruption of natural weather systems.

Is loading

Silver concentrations in the Snowy Mountains have increased since 2013, but are still “several orders of magnitude” below guideline levels, according to the Environmental Protection Agency. Silver occurs naturally in the environment and Siems said the amount spread over the mountains each year is equivalent to the amount a dust storm could transport.

The effect of cloud seeding on reducing downwind rain or snowfall is currently being researched, although the precipitation caused by cloud seeding often would not have fallen anyway, Siems said.

Some jurisdictions in the U.S. use cloud seeding to prevent hailstorms because these seedings produce many small hailstones rather than large, destructive chunks of ice. Other applications being considered include using cloud seeding to create rain over wildfires, which would likely not work.

“These are rare events,” said Siems. “I am more skeptical about these things because it is so much more difficult to achieve statistical certainty.”

The Examine newsletter explains and analyzes scientific findings, focusing consistently on the evidence. Sign up to receive it every week.