Did a cloud-seeding start-up really increase snowfall in part of Utah?

States like Utah in the western US have been suffering from a record snow drought, raising fears of wildfires and low flow in the crucial Colorado river. But a start-up that releases negatively charged aerosols that can be carried up into clouds claims it has increased snowfall by 20 per cent in one Utah mountain range.

Rain Enhancement Technologies compared snowfall in the La Sal mountains and the Abajo mountains 70 kilometres to the south during five recent dry winters. When the company was operating its high-voltage ionising array upwind of the La Sal mountains in January, the range received 9 centimetres more snow than would have been expected given the amount of snow the Abajo mountains got, the company says.

But scientists caution that these results could have occurred by chance and it is too early to tell how well the technique works.

“Cloud-seeding operations have been active for quite some time and we are offering another means of enhancing precipitation… but one which doesn’t involve any chemicals,” says the company’s meteorologist Jeff Chagnon. “We also don’t have to fly into clouds… We can just flip a switch from anywhere in the world and operate for about 48 hours at a time.”

The United Nations warns that the world is entering an era of “water bankruptcy”, with up to 3 in 4 people facing water scarcity or contamination. Countries like Iran, where water shortages helped fuel bloody protests, have been trying to induce more rain by spraying salts such as silver iodide from aeroplanes. Nine US states also have cloud-seeding programmes.

But the public has often been concerned by the unknown health effects of silver iodide being released in large quantities, while conspiracy theories around “chemtrails” fuel mistrust about supposed weather modification programmes. Ten US states have banned or considered banning cloud seeding.

Rain Enhancement Technologies has been running 10,000 volts of electricity through a coiled wire suspended between a pair of 8-metre pylons. Tiny aerosols like dust, soot or salt pick up electrons when they blow near this wire, much like your feet can pick up charge when they rub on a carpet. The wind then carries some of these ionised particles up into clouds.

Water naturally condenses onto aerosols in clouds to create droplets that move around and collide with each other. If they stick together, they can fall to Earth as rain. Droplets often don’t stick, however, and so remain too small for gravity to overcome the updraft keeping them aloft.

But electrically charged droplets – even those of the same charge – interact to form a polarity, with the negative side of one droplet attracting the positive side of another. When droplets condense around Rain Enhancement Technologies’ negatively charged aerosols, the attraction between them speeds up the rate of collision and coalescence that produces rainfall, according to Chagnon.

The technology can’t drive the upward movement of air that generates clouds and rain. “But once the cloud is formed, we can get a little more water out of that cloud,” says Chagnon.

Evidence from the cold war suggested that electric charge can enlarge cloud droplets. A 2020 analysis found there was 24 per cent more rain over the Shetland Islands in the UK on days when radioactivity from nuclear bomb tests had ionised the air.

A Rain Enhancement Technologies trial in Oman from 2013 to 2018 increased rainfall by 10 to 14 per cent, depending on the statistical analysis used, a study found. An experiment that dispersed negative ions from a similar array in China claimed to have boosted precipitation by about 20 per cent.

But the World Meteorological Organization warns that while spreading salts in winter clouds has been shown to affect precipitation, the ionisation approach still lacks scientific proof.

“It’s interesting that they have seen something that is consistent with a modification of clouds,” says Edward Gryspeerdt at Imperial College London. “But because precipitation, snowfall, rainfall is incredibly variable, there is always a significant chance that the effect they’ve seen has just happened by chance.”

The five dry years that Rain Enhancement Technologies used to set the baseline in the Utah mountain ranges may not be enough to fully account for how much difference can be seen in the snowpack across seasons, says Jeff French at the University of Wyoming.

“I would wait for further experimental studies and for more years to confirm the validity of ionisation as a catalyst for additional snow,” says Ibrahim Oroud at Mutah University in Jordan.