For centuries mankind has dreamed of changing the weather at will, to reverse drought, stave off destructive storms or to water crops.
Climate change aside, most of those attempts have been little more than wishful thinking. But when the snow begins to fall in Kosciuszko National Park in a few short months time, it will be getting a helping hand – from a utilities company.
Officials with electricity generator Snowy Hydro are installing a series of burners along the western edge of Kosciusko national park. Those burners are part of a large network of equipment and expertise the company plans to use to increase the amount of snow falling in the NSW alps this winter.
With more than 10 years of scientific trials complete, the company has been given the green light by the NSW Government to conduct regular cloud seeding operations, a move that has some environmentalists worried, despite the strict operating restrictions placed on the program.
Snowy Hydro manager of scientific services Karen Kemsley says while there has been much debate in the past about whether cloud seeding actually works, the extensive trials have proven the company can increase the amount of snow falling by about 14 per cent by targeting the right clouds as they pass overhead.
"It's not that we're actually making it snow, because we're only allowed to cloud seed into clouds that were going to snow anyway. What we're doing is squeezing a little extra out of those clouds."
Experiments with increasing rain or snow date back to the 1940s, when American scientists working for General Electric discovered that dropping dry ice into a box containing chilled water vapour caused ice crystals to form.
Atmospheric tests soon followed with mixed success, as planes loaded with dry ice were flown into clouds to release their payloads.
Initial excitement about the potential for the technology to be used as a drought-breaker soon followed, and regions around the globe, from Russia to Asia, began to roll out large-scale cloud-seeding programs either to create rain, or to try and prevent it.
Rumours have long persisted that the Americans, one of the most enthusiastic adopters of the technology, also invested heavily in research during the Cold War era into weaponising the weather so it could be used to direct destructive storms over hostile territory.
While little evidence exists to support the conspiracy theories, the US did use cloud seeding for military purposes during the Vietnam War, according to The New York Times.
In July 1972 legendary journalist Seymour Hersh reported that the US had been conducting a highly classified cloud-seeding program known as Operation Popeye on a massive scale over North Vietnam, Laos and South Vietnam to increase and control rainfall. By dumping silver iodide and lead iodide into clouds, the Americans were reportedly able to extend the monsoon season by more than a month over the Ho Chi Minh Trail, softening roads to cause disruption to military trucks using the area.
China too, has been one of the most enthusiastic adopters of weather modification. The world was given a glimpse of that enthusiasm in the lead-up to the 2008 Olympics when Beijing's Weather Modification Office launched a barrage of 1100 rockets containing silver iodide into the sky from 21 sites across the city the day before the opening ceremony to disperse clouds and keep the event rain-free. China has high hopes the technology will help alleviate drought in the country's north.
China reportedly employs about 50,000 people in various cloud seeding programs and hopes to generate up to 55 billion metric tons of artificial rain a year. There are even private companies in some countries offering a service to brides that claim to be able to seed clouds to ensure it doesn't rain on the wedding day.
While Australia's programs have not been as ambitious as the Chinese, the country has also long dabbled with cloud seeding, investing significantly in studies run by the CSIRO and others since the 1940s.
Promising results in the 1960s and '70s led Hydro Tasmania to set up a cloud seeding program which last year resulted in 30 cloud seeding flights over the island state's water catchments. There have also been trials of warm cloud seeding (a different technology to that used in NSW) over Queensland and other parts of the country in recent years.
Victoria, along with NSW and Tasmania, is regarded as one of the few locations in the country where cold cloud seeding is potentially viable, due to its weather and geography. According to the Department of Sustainability and Environment, a number of cloud seeding trials have been conducted in the state, including over the Thomson catchment from 1988-1992, that it was hoped would boost water storage levels.
In 2008 the Victorian state government issued a paper announcing it had decided against pursing the technology any further, citing ongoing uncertainties about the efficacy of cloud seeding and its commercial viability, although the paper said authorities would watch with interest results from other states and continued advances in the technology.
In NSW, attempts to bring cloud seeding back to the high country after some ambiguous early experiment results began in earnest in 2004 with the start of the Snowy Precipitation Enhancement Research Project. Initial trials were extended to 2014, but the program was given an early go ahead in 2013 when the NSW Parliament fast tracked its approval, citing overwhelming evidence of its success and scientific findings that it did not harm the environment.
The Snowy Mountains operation is limited to ground based generators that target cold fronts sweeping over from the west during the colder months and can only operate under specific weather conditions. Smallish green sheds with a short tower on their side mix silver iodide with a solvent and spray them into a gas burner. Winds sweeping up the side of the mountains carries the seeding agent into the clouds.
In the winter of 2013 Snowy Hydro spent 106 hours burning nearly 45 kilograms of silver iodide into passing clouds, and a further 68 hours during the winter of 2014.
This year, the network of 23 cloud seeding generators are again being positioned along the western edge of the park, and will be ignited when clouds likely to produce snow down to 1400 metres pass overhead.
Kemsley says unlike during the trials, they will be using every available opportunity to get the maximum amount of extra precipitation out of the passing cold fronts.
"One of the biggest concerns that people have raised in the past has been environmental concerns.
"But we have strict environmental management plans that we have to report to government that impose a lot of requirements on us."
Those reports have to date found no elevated levels of silver iodide in or downwind of the 2100sq km target area, and no evidence that increased amounts of snow were having a negative impact on wildlife or plants in the park.
The studies have also dismissed concerns that taking extra moisture out of clouds in one location may rob those downwind of rain.
But some, including NSW Greens MP Mehreen Faruqi, remain wary of the program.
In the latest National Resources Commission report into the trial released in 2010, the authors raised concern that there was not enough information on what happened to the cloud seeding agents once they were dispersed.
"Although no adverse environmental effects have been detected to date, it is an important matter for future risk analysis to understand the ultimate fate of these seeding chemicals," the report said.
Dr Faruqi says the program should never have been allowed to move out of the trial phase before answering those concerns.
"There is nothing to tell us how those chemicals accumulates in the environment. We are worried about those chemicals entering the food chain of critically endangered animals like the pygmy possum and the corroboree frog.
"When we don't know longer term impacts we have to take a precautionary approach, not just 10 years. We have to learn our lessons from the past, things like DDT, asbestos, CFCs, the impact of these chemicals accumulating became apparent decades after they started being used."
Dr Faruqi believes that rather than try to alter natural weather patterns to create energy, the focus should be shifted to well-established alternatives like solar and wind power that do not require tampering with the environment's natural cycles.
Snowy Hydro senior atmospheric scientist Andrew Peace says in the overall scale of the winter weather systems of the region, cloud seeding plays a relatively small role.
"We get accused of some interesting things like chemtrails (chemical or biological agents believedly sprayed into the atmosphere for sinister purposes) but the scope of where cloud seeding can be used is fairly limited, basically just where it is used now in NSW, Tasmania, and also parts of Victoria."
One of the biggest problems cloud seeding advocates have faced, is proving that the recorded snow wouldn't have fallen naturally anyway.
In 2010 researchers at Tel Aviv university examined over 50 years of data on cloud seeding and concluded that in most cases, measured increases in precipitation could be explained by changes in weather patterns, rather than direct intervention by cloud seeding. The notable exception to their findings was in places where extra rain could be coaxed out of orographic clouds formed by air being pushed up over mountains – as happens in the Snowy Mountains.
Under the operating conditions imposed on Snowy Hydro, scientists are only allowed to target clouds likely to produce snow down to 1400 metres, making it difficult to determine how much would have fallen without human intervention.
Elaborate wind fences have been set up around measuring stations and trials deliberately left some clouds unseeded to measure the difference between those that had been targeted. Operators measuring snowfalls were also kept in the dark about when clouds were seeded as part of blind tests.
Despite the confidence scientists involved with the program have in the 14 per cent increase figure they have arrived at, just how much extra water is produced (and more importantly for Snowy Hydro how much money can be earned sending that water through its turbines) remains a difficult question to answer.
"There are many things to consider, for example, how much and where the snow has fallen, how much snow evaporates, melts or replenishes groundwater storage," says Kemsley.
Then deputy Premier Andrew Stoner was less conservative with his figures when making a case to the NSW Parliament in 2012 for allowing the program to move from its trial phase.
"The additional amount of electricity is estimated at 36 gigawatts per annum which, if produced by a NSW coal plant, would emit the equivalent of over 28,000 tonnes of carbon dioxide emissions annually and burn more than 12,000 tonnes of black coal."
Figures provided to Mr Stoner's office also predicted the move to full operation would lead to an extra 20 gigalitres of water being produced every year.
And while the ski resorts and downstream irrigators welcome any increase in precipitation, Snowy Hydro still can't say exactly what the program costs, or how much money they make out of it.
"It's something that we're still working on. I guess the answer is we wouldn't be doing it if it wasn't (profitable)," says Kemsley.
And while the trial has been deemed a success, Kemsley says it is important people understand the scale of the operation and that it is not going to guarantee a bumper ski season or solve the next 10-year drought.
"It's more an incremental effect, it's obviously boosting the snow pack, but it's not doubling it.
"What you try and do is seed when there are ample opportunities so you augment water supplies so there is extra storage to use during droughts, you can't create clouds when there's a drought on."
Barring major changes to the weather that would make the technology unviable, Kemsley expects cloud seeding to be a part of the long-term management of water storages in Kosciuszko region.
"The plan is to keep going as we are, because of the results we've had from the trial. I think it's a testament to Snowy that it has been a project with an innovative vision, with all the spin-off research projects that have come out of it, it has been a great achievement that I hope keeps going."
