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Gone But Not Forgotten
Aug 18, 2002
Seeds of doubt? Researchers question the science behind cloud seeding

By Greg Lavine
The Salt Lake Tribune

Since the first practical cloud-seeding experiments took place more than 50 years ago in upstate New York, groups around the world -- including some in Utah -- have embraced the goal of squeezing extra moisture from overcast skies.

Utah counties and water-conservation groups have been regularly seeding clouds since 1973 to build snowpacks. The idea is to enhance nature's winter precipitation to avoid water shortages in the summer.

But a report from the National Academies' National Research Council last fall calls into question whether attempts at cloud seeding to increase snowfall, reduce hail or suppress fog are scientifically valid. The report finds no hard, scientific evidence to prove or disprove the value of ongoing cloud-seeding efforts.

"There are still some fundamental questions that need to be answered," said Daniel Breed, a researcher with the National Center for Atmospheric Research in Boulder, Colo., who helped edit the report. "There really is a dying need for information in this area because people are doing these projects regardless."
More Information

The report has kicked up a flurry of controversy between some meteorology researchers and cloud-seeding backers. According to the report, 24 countries engaged in weather modification in 2001, including 66 programs in 10 U.S. states.

Cloud seeders argue that if meteorologists cannot even predict the weather with complete accuracy, then weather-modification advocates should not be required to meet science's exacting standards for proof. Weather-modification groups point to mathematical formulas that indicate the benefits of cloud seeding.

Part of the debate centers on what are known as confidence intervals. Scientists prefer research that shows at least a 95 percent confidence interval, meaning that there is only a 5 percent chance that any given action is doing nothing.

Don Griffith, of Salt Lake City's North American Weather Consultants, said that the 95 percent gold standard is unreasonable for activities such as cloud seeding. Griffith's company handles most of Utah's cloud-seeding programs as well as similar projects in Idaho and California.

"Weather forecasting is not always 95 percent right," Griffith said. "Does that mean we shouldn't do weather forecasting? I don't think so."

Breed said that while weather systems are complex to understand, more rigorous evaluation is needed to make better-educated guesses about whether cloud seeding actually brings rain or snow. Part of the report indicates a need for more research into the questions surrounding cloud seeding.

Improved radar and satellite technology could be employed to learn more about the physical processes going on inside the clouds, Breed said. Until then, it remains unclear whether all the predicted sequence of events involved in cloud seeding are in fact taking place.

Utah's cloud-seeding efforts normally take place between Nov. 15 and April 15, Griffith said. This year, programs are under way in Box Elder and Cache counties, the high and low Uinta Mountains and ranges in south-central Utah. There are no active cloud-seeding projects along the Wasatch Front.

Cloud-seeding generators are scattered among residential areas up to 20 miles west of the mountains. When the right cloud system approaches, Griffith's company tells residents to turn on seed generators installed on their property.

A propane flame burns a mix of acetone and silver iodide, the future nucleus of potential snowflakes. The acetone burns off, leaving the silver iodide to float up into the clouds.

These silver iodide seeds gather moisture in the cloud until they become heavy enough to form a snowflake that falls to the ground, adding to the snowpack.

In an average winter, about 25 such storms rumble across Utah. Nearly all of these cloud systems would have yielded snow even without the silver iodide. Griffith said that the seed generators aim to enhance the snowfall, not make precipitation from nothing.

But measuring success can be a problem.

"It's kind of the old question," Griffith said. "If we hadn't seeded the cloud, how much snow would we have gotten?"

Griffith said his company's analysis estimates a 10-18 percent increase in snowfall in any given year.

" It's by no means a drought-buster," Adams said. Still, even a modest increase in precipitation is worthwhile for those living in such a dry state, he said.

Utah officials see these and other statistics as being worth the 0,000 they spend each year on cloud-seeding projects, said Todd Adams of the state Department of Natural Resources' Division of Water Resources.

Adams said the state does not initiate any such programs, but it does offer a pool of money to share costs with counties and water-conservation districts who hire a weather-modification company. North American Weather Consultants is one of two companies licensed in Utah to provide cloud-seeding services.

The report will not affect Utah's future cloud-seeding plans, Adams said.

The Weather Modification Association, an industry advocacy group, is drafting its own report in response to the National Academies paper, said Griffith, whose company is a member. An initial statement from the group criticized the high scientific standards requested, but agreed with the need for more research.

Breed said he hopes funding will become available for research using today's technology, which could clear the air over the lingering cloud-seeding debate.

A storm is brewing in China as drought-plagued regions accuse each other of stealing clouds for rain-seeding.

With the help of modern technology, scientists can fire rockets filled with various substances into light, fluffy clouds to make them rain.

"But the practice has caused considerable controversy in recent days, with some saying that one area's success with rain has meant taking moisture meant for one place and giving it to another," the China Daily said on Wednesday.

The row over rainclouds was particularly heated in several cities in central Henan province.

"Meteorological officials in Zhoukou were soon accusing their counterparts in Pingdingshan of overusing available natural resources by intercepting clouds that would have likely drifted to other places, say, like Zhoukou," the newspaper said.

Much of China is short of water and cloud-seeding is common, especially over major cities.
Silver lining that could not find the right cloud

A CHINESE military aircraft trying to trigger rain over a sweltering Shanghai, the country’s financial centre, failed because it could not find the right clouds.
Demand for power during a three-week heatwave, as citizens cranked up the air-conditioning to offset the 35C (95F) heat, has caused an energy shortfall equivalent to a year’s supply for 40 million American households.

The lights have been switched off on Shanghai’s famous riverside promenade, the Bund, and the local government has told thousands of factories to work at night, when it is cooler. Restaurants and hotels in the city of about 20 million people have been ordered to keep air-conditioning to a minimum.

Runaway economic growth in China has led to an unprecedented rise in demand for electricity in the big cities and wealthy coastal regions.

However, a lack of significant investment in modern forms of electricity generation, combined with widespread inefficiencies in the energy industry, has led to regular power shortages. The energy shortfall in Shanghai this year could be as high as four million kilowatts.

Cloud seeding is an increasingly common practice in China to offset the effects of drought. Much of the country is short of water and many water tables are dropping at an alarming rate.

In many cities and regions, rockets and even anti-aircraft guns have been used to seed the clouds and many local governments have set up special weather bureaux to try to bring down the rain.

The seeding technique, invented in the 1940s, involves injecting particles into a cloud, which act as freezing nuclei. Cloud droplets stick to the injected particles and fall as rain or snow. But without the right sort of clouds, the seeding technique makes no difference.

The earliest attempts at cloud seeding involved dropping crushed dry ice, or carbon dioxide, pellets into the top of a cloud from an aircraft. Later, scientists started to use silver iodide because it was a better cloud-seeding agent.

There is a debate among meteorologists about the effectiveness of cloud seeding, although most agree that the principle is sound. Some studies show that cloud seeding can increase precipitation by up to 30 per cent, but others are wary of the overall effect on the environment.

A military aircraft took off this week from Wuxi near Shanghai and flew around for about an hour before releasing rain-inducing silver iodide, but it failed to raise an umbrella in the city. The Shanghai Daily newspaper said that the aircraft had failed to find clouds of the ideal type. The plan did prompt about 20 minutes of rain in the district of Fengxian near by, but not enough to bring the mercury down significantly.

According to local media, cloud seeding over Shanghai was first tried in 1960, when the military had just as little success in trying to make rain.

Another attempted cloud seeding this month failed when the aircraft ran into real clouds and a thunderstorm after take-off.

A power shortage in Shanghai last year forced hundreds of firms to trim output.

The local weather bureau in Shanghai has invited four meteorologists experienced in cloud seeding to visit the city from the northeastern


Kicking up a storm with the cloud seeders

* 16 April 2005
* From New Scientist Print Edition. Subscribe and get 4 free issues.
* Kate Ravilious
* Kate Ravilious is a science journalist based in Edinburgh in the UK

CANONS blazed and aircraft deployed their payloads, but not a drop of blood was shed in the battle between the cities of Pingdingshan and Zhoukou in Henan province, China, on 10 July last year. That's because their targets weren't people, but clouds.

The blistering dry spell that struck the province threatened to cause water shortages and ruin crops. The problem was frustratingly clear: though clouds drifted across the skies, too few would give up their water as rain. To coax the water out, Pingdingshan meteorologists decided to resort to a controversial practice they believed would help the heavens break, called cloud seeding. Anti-aircraft guns and rockets were used to bombard pregnant clouds with a fine spray of silver iodide crystals in the hope they would prompt large droplets to form in the cloud, and thus produce more rain.

A few hours later it looked like their gambit had paid off. Westerly winds blew the clouds over Pingdingshan, where they dropped 10 centimetres of rain. But later that day only 2.5 centimetres of rain fell over Zhoukou, further east.

Meteorologists at Zhoukou cried foul. In the war of words that followed, they claimed Pingdingshan's cloud seeding had caused rain that would have fallen over Zhoukou to fall early. Nonsense, Pingdingshan officials retorted: clouds are complex systems, and seeding shouldn't affect the chance of rain 120 kilometres away.

"There's no scientific evidence that cloud seeding can dry clouds out," says Yan Yin, an atmospheric physicist at the University of Wales in Aberystwyth, UK. "But I'm not surprised they quarrelled. In China the effectiveness of cloud seeding is an article of faith. They seed clouds all the time." Indeed, 23 of its 34 provinces have "weather modification bureaux" and routinely seed clouds. But does showering a cloud with chemical particles really cause more rain to fall?

Take a glance at many other countries around the world and you'd be forgiven for thinking the answer is a clear-cut yes. Australia, the United States, Israel, South Africa, Russia and India all have extensive private or public cloud seeding programmes, some of which have been operating for over 50 years (see Map). Governments and businesses spend millions in the hope of wringing moisture from the clouds.

In reality the facts are far from clear. "There's no good statistical proof that cloud seeding produces more rainfall than not seeding," says Phil Brown, manager of cloud physics research at the UK's Met Office in Exeter. And even though meteorologists know how cloud seeding is supposed to work, it is difficult to measure its effectiveness. "You have to prove it was your seeding that produced the rainfall increase rather than some other effect," says Brown. And that is no mean feat.

Proof that it works will bring great rewards. Fresh water is fast becoming one of the most valuable resources on the planet. That is why scientists all over the world have spent the past 50 years trying to prove cloud seeding works. To date, no experiment has proved conclusive either way. But now a team from South Africa has completed the first long-term study of cloud seeding, and the researchers believe they at last have the evidence that, under certain conditions, cloud seeding really does increase rainfall. They claim that their method can increase the mass of water droplets in a cloud - and therefore the amount of rainfall - by up to 60 per cent (see Graph).

Clouds form in two phases. When there is enough water vapour in the air, water can condense onto naturally occurring hygroscopic - moisture absorbing - particles (such as salt crystals or dust) called cloud condensation nuclei (CCNs), to form microscopic droplets.

If the droplets are lifted by air currents, the falling temperature and pressure increase the relative humidity to a point where they can absorb more water and grow far larger. These can fall as drizzle - 100-micrometre droplets - or rain, with droplets larger than 1 millimetre (see Diagram).

In really cold clouds (below -38 °C) there is an additional stage. As the moist air rises the droplets freeze. These ice crystals can continue to grow if they collide with other ice crystals. When they fall, the air temperature below the cloud determines whether they reach the ground as snow, or melt and fall as rain.
“Anti-aircraft guns and rockets were used to bombard pregnant clouds”

The aim of cloud seeding is to optimise the number of droplets that form in the cloud. This is tricky. Small cloud droplets tend to grow faster than large ones, so you often end up with droplets of similar size, which therefore fall at the same speed and seldom collide - meaning no rain. Only clouds with a variety of droplet sizes will produce rain. So, the key to cloud seeding is introducing the optimum number of CCNs into a cloud - too few and the droplets won't form, too many and you end up with lots of tiny droplets that don't coalesce enough to fall out of the sky.

Because of their differing precipitation mechanisms, cold clouds and warm clouds require different seeding methods. Cold cloud seeding was discovered accidentally in 1946 by Vincent Schaefer, a scientist working at the General Electric labs in New York. He observed that spraying crystals of frozen carbon dioxide into a cold cloud chamber helped ice crystals to form. He reasoned that scattering dry ice into cold clouds would have the same effect, helping initiate precipitation. In his first trial, he scattered 1.5 kilograms of crushed dry ice into stratocumulus clouds over western Massachusetts. Because dry ice is cumbersome to carry by plane, he later switched to silver iodide - a chemical with a similar molecular structure to ice crystals - as the seed, hoping it would kick-start crystal formation in a similar way to carbon dioxide. Though the experiments were inconclusive, the idea gained attention and became known as glaciogenic seeding.

Warm cloud seeding didn't arrive until 1989. A group of South African scientists, led by the late Graeme Mather, were using an aircraft to measure the droplet properties of various clouds as part of a cold cloud seeding study. One day they sampled a very unusual cumulus cloud above a large paper mill. It had exceptionally large droplets - around half a centimetre wide - in its updrafts and a surprisingly wide range of droplet sizes at its base.

Unlike other cumulus clouds they studied, the cloud above the paper mill was producing big drops of rain. Mather and his colleagues worked out that the paper mill was inadvertently seeding the cloud above because it pumped hygroscopic particles that acted as CCNs out of its chimney stack. They were the first to realise that the large particle size was crucial, and that mimicking these hygroscopic particles could be a way to seed warm clouds and produce large raindrops. The most hygroscopic natural CCN material is common salt, so they decided to test warm cloud seeding using flares stuffed with salt crystals strapped to an aircraft wing.
“Seeding a quarter of the clouds might increase rain by up to 10 per cent”

Early trials were encouraging, so in 1991 Mather and his team gave up on glaciogenic seeding and started an extensive long-term hygroscopic cloud seeding trial. They devised a blind, randomised, controlled experiment, and over the course of five summers in the Highveld region of South Africa they sampled 127 warm convective storm clouds - 62 seeded and 65 left as controls. Mather's team used airborne radar to measure the average density of droplets in the clouds, which they believed would give a good indication of how much rain the cloud would produce. When they compared the data from seeded and unseeded storm clouds, they found seeding really was having an effect. "Seeded clouds evolved to have a longer duration, larger area and higher liquid content," says André Görgens, a water resources engineer on the team. On average the total mass of water droplets formed in one hour inside a seeded cloud was 60 per cent larger than for an unseeded cloud.

As a result the South African government funded the team to carry out experimental seeding programmes in the drought-stricken Limpopo province in 1997. The aim was to seed as many suitable storm clouds as possible with full scientific monitoring, and then carry out a cost-benefit analysis and environmental assessment. Over the past four years Görgens and his colleagues have been analysing the data gathered during the programme and published several papers on their findings (Water South Africa, vol 30, special edition, p 88).

They calculated that seeding just a quarter of the storm clouds in the Limpopo province would increase average rainfall by up to 10 per cent. And Görgens's cost-benefit analysis concluded that the benefits of cloud seeding outweigh the costs by a factor of 1.7. "Cloud seeding helps to keep the reservoir levels up and enables an increase in rain-fed agricultural output, such as maize, grazing and timber production," he says.

Yin is impressed with Görgens's study. "These results are based on a statistically sound experiment and can be trusted," he says. And that's rare for cloud seeding experiments.
It's rain that matters

But there is one uncomfortable hole in Görgens's trial, as Peter Hobbs, an atmospheric physicist at the University of Washington in Seattle, points out. It's not enough to measure the density of drops in a cloud, he says. Where is the proof that the raindrops hit the ground? "Seeding can change the structure of clouds, but it is a different issue as to whether it increases rainfall." Hobbs thinks the only way to be sure is to design an experiment with a dense network of gauges to measure rainfall on the ground.

Görgens agrees that such measurements would be desirable, but says he has anecdotal evidence from local farmers that rainfall increased during storms he seeded. In future tests he hopes they will get a more accurate impression of rainfall thanks to a network of weather radars that is currently being set up across South Africa.

And of course, even if cloud seeding does work, it can only squeeze rain from existing clouds, not create new ones. "Most areas that are short of rain are also short of clouds, and you can't seed if there aren't any clouds," says Hobbs.

On the other hand, one of the major advantages of hygroscopic seeding is that warm cumulus clouds do tend to pop up in arid areas, unlike the large cold clouds required for glaciogenic seeding. Roelof Bruintjes, now at the National Center for Atmospheric Research in Colorado, and originally a member of Mather's South African cloud-seeding team, has exported the hygroscopic seeding method to other arid areas in the world.

Between 1996 and 1999 he reproduced Mather's South African experiments in Mexico and recorded increases in droplet density of up to 30 per cent. Last year he finished a feasibility study of hygroscopic seeding in the deserts of the United Arab Emirates. Clouds are rare in the UAE, but Bruintjes reckons he has found some suitable candidates. "During the summer months thunderstorms build over the Oman Mountains, and these are feasible clouds for hygroscopic seeding," he says. He is now analysing the results, and if they are positive, he expects to start a full seeding programme in the near future.

Glaciogenic seeding has had a more chequered past. To date, most studies appear to fall short in scientific rigour. Hobbs is dismissive of studies from Israel and Colorado. "When I re-analysed their results I found that the experiments hadn't been randomised properly and they didn't have enough trials to reach statistical significance," he says.

All this could be about to change. Up in the Snowy Mountains in New South Wales, Australia, hydroelectric power company Snowy Hydro is one year into a six-year trial to see if glaciogenic cloud seeding will make winter snows heavier. Rather than spray silver iodide from aeroplanes, they are using ground-based generators that spray it directly into clouds as they rise over the mountainside. Just like the South Africa experiments, they have designed their trials to be double blind. They will monitor the clouds with radar and use a dense network of snow gauges to measure any change in snowfall at the surface.

But could cloud seeding be dangerous? Some people worry that seeding a heavily laden cloud could cause flash floods (see "Murky past of cloud seeding"). "It is not beyond the bounds of possibility," says Hobbs, "but I personally doubt it." Görgens thinks that choosing your clouds carefully will eliminate the risk of floods. However, he admits the extra water could attract more insects. Others are concerned about silver iodide pollution. But Mark Heggli of Snowy Hydro says his ground measurements after seeding have barely detected even trace levels - too low to be a danger to human health. "You get a bigger dose of silver from fillings in your teeth," he says.

Perhaps the greatest worry is the potential for cloud seeding to be used as a weapon. In 1977 the UN General Assembly adopted a resolution prohibiting the hostile use of environmental modification techniques. Yet nine years ago the US air force commissioned a report entitled Weather as a Force Multiplier: Owning the weather in 2025. The report concludes, "Over the course of the next century, the weather will be our most powerful weapon. Weather modification can provide battlespace dominance to a degree never before imagined. By 2025 it will be in the realm of possibility."

Görgens prefers to focus on the benefits of cloud seeding. He cites indigenous tribes such as the Pedi, who live in the bushveld of the Limpopo province, as potential beneficiaries. "These people live by subsistence farming and they are very vulnerable to a shortfall in the rain. Warm cloud seeding would bring more reliable rains for them."

When Snowy Hydro's experiment is concluded we should also have a clearer picture of the effects of glaciogenic seeding, by far the most popular method around the world at the moment. But even if the results are positive, it won't clear up the controversy around cloud seeding. Just ask the people of Zhoukou.
From issue 2495 of New Scientist magazine, 16 April 2005, page 40
Murky past of cloud seeding

On 15 August 1952, the people of Lynmouth in south-west England experienced a downpour like never before. The ensuing floods killed 34 people and left 420 more homeless. At the time rumours circulated that the flood could have been the result of cloud seeding trials that the Royal Air Force was conducting nearby. However, few people now think that the cloud seeding was to blame, because the RAF was seeding cumulus clouds, while the rain that deluged Lynmouth came from a large depression sitting over the region.

In 1966 the US military began operational flights on the CIA-inspired, top secret "Project Popeye". Their aim was to extend the monsoon season over south-east Asia, thereby increasing the amount of mud on the Ho Chi Minh Trail and flooding critical routes between what were then North Vietnam and South Vietnam. For seven years, aircraft flew more than 2600 sorties to disperse silver iodide into the clouds over the region, and initial results were positive, although analysts remain divided as to whether the extra mud on the trail really made much difference.

On 9 June 1972, 238 people lost their lives in floods in Rapid City, South Dakota, when nearly a year's worth of rain fell in just a few hours. Cloud seeding had been carried out nearby earlier in the day and many people believed this triggered the storm. But Harold Orville, who was involved with the seeding programme, is certain that it was not responsible. "Our seeding was done on the plains, 20 or 30 miles from the area where the heavy rains fell. Numerical simulations of the weather that day suggest that the flood would have happened anyway," he says.


Silver nitrate

Hey there,

I'm sure I read in some sci-tech paper that there was a process that involved loading clouds with silver nitrate to induce rain to fall. A crude type of weather control and a long way from the sort of thing shown in Back to the Future II!!!!!!

Wasn't it Artur C Clark who prophesised man controlling the weather??
AFAIK, it's disputed. People selling rain-seeding gear talk it up; others talk it down. The bottom line is that it's very hard to prove a correlation between seeding and rain; how can you prove that it would not have rained then anyway? It doesn't help that it's generally used in unusual circumstances.

The military have tried it - there was an unsuccessful attempt to close the Ho Chi Minh trail this way. But it's currently illegal and takes a lot of resources.
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Seeding for rain is not illegal, at least not here. Many drought affected areas of the country have been using it to try and induce rain.

The idea behind it is sound. Rain needs something to act as the nucleus to the droplets, in order for them to condense and precipitate from the water vapour in clouds. So, in order to force clouds to drop their water, spray some fine particles into them, hopefully forcing drops to form. (Silver nitrate is used because of the size of the particles - they're nice and small and, in theory, should prompt rain to form well.)

The problem is that seeding is only about 50% effective. Or, more accurately, only about 50% of clouds that are seeded produce rain where it is wanted. There is a distinct possibility that the seeding is having absolutely no effect at all, and that the rain attributed to it is just coincidental.
Futuristic fleet of 'cloudseeders'

Some experts are proposing radical ideas to save us from disastrous climate change. But would they work? Professors John Latham and Stephen Salter have designed a fleet of yachts that would pump fine particles of sea-water into clouds, thickening them to reflect more of the Sun's rays. Here, Professor Latham talks about the proposal.

It was in 1946 that scientists first began trying to manipulate clouds.

They found that by firing tiny particles of silver iodide into rain-bearing clouds, they could induce rainfall.

Our idea of a fleet of "cloudseeders", however, was largely born from a remark made by my son Mike, decades ago.

We were on a mountainside in North Wales, looking west towards Ireland.

He asked why clouds were shiny at the top but dark at the bottom.

I explained how they were mirrors for incoming sunlight.

He pondered for a while, then grinned: "Soggy mirrors, Dad," he said.

The idea my colleagues and I are pursuing is to increase the amount of sunlight reflected back into space from the tops of thin, low-level clouds (marine stratocumuli, which cover about a quarter of the world's oceanic surface), thereby producing a cooling effect.

Calculations show that if we can increase the reflectivity by about 3%, the cooling will balance the global warming caused by increased CO2 in the atmosphere (resulting from the burning of fossil fuels).

Cloud-seeding yachts

In order to deploy our scheme and produce adequate cooling, we would need to spray sea-water droplets continuously over a significant fraction of the world's oceanic surface, at a total rate of around 50 cubic metres per second.

Professor Stephen Salter has developed plans for a novel form of spray-droplet production (involving high-velocity propulsion of sea-water droplets), and has designed a wind-powered unmanned vessel which can be remotely guided to regions where cloud seeding is most favourable.

Instead of sails, these vessels use a much more efficient technique to power the yacht - Flettner rotors.

These spinning vertical cylinders mounted on the deck, are named after their inventor Anton Flettner. They also house the spraying system which sprays sea water droplets from the top of the rotors.

The power required for spraying, communications and so on, comes from electricity generated by turbines dragged along by the vessels.

We envisage that about 1,000 such vessels would be required to make the scheme effective.

Under control

The ideal solution to the global warming problem is that the burning of fossil fuels be drastically reduced.

But our scheme offers the possibility that we could buy time within which catastrophic warming could be staved off while carbon dioxide levels are being reduced to acceptable levels.

One advantage of our plan is that it is ecologically benign, the only raw material required being sea-water.

The amount of cooling could be controlled, via satellite measurements and a computer model, and if an emergency arose, the system could be switched off, with conditions returning to normal within a few days.

In addition to global temperature stabilisation, we also envisage that the technique could be used to remedy more regional problems, such as the dying of the coral reefs as a result of ocean warming.

Long road ahead

But while it is all very well spraying the clouds, what effect will this have on the world's fragile eco-system, and do we have the right to interfere with the planet in this way?

Before we could justify deploying such a scheme on a global scale we would need to do several things.

We would have to complete the development of the required technology, and conduct a limited-area field experiment in which the reflectivity of seeded clouds is compared with that of adjacent unseeded ones.

We would also have to perform detailed analysis to establish whether there might be serious or harmful meteorological or climatological ramifications (such as reducing rainfall in regions where water is scarce) and if so, to find a solution for them.

But bearing all this in mind, we have been encouraged by the consistent response we have received to our scheme - for example at a recent Nasa meeting - and it seems likely to be a strong contender in the fight to improve the current global warming problem worldwide.

When the planet is in such a dire situation, I am convinced it is simply irresponsible not to at least examine our options.

Full text at link.

Cloud-seeding ships could combat climate change

Cloud seeding on the high seasIt should be possible to counteract the global warming associated with a doubling of carbon dioxide levels by enhancing the reflectivity of low-lying clouds above the oceans, according to researchers in the US and UK. John Latham of the National Center for Atmospheric Research in Boulder, US, and colleagues say that this can be done using a worldwide fleet of autonomous ships spraying salt water into the air.

Clouds are a key component of the Earth’s climate system. They can both heat the planet by trapping the longer-wavelength radiation given off from the Earth’s surface and cool it by reflecting incoming shorter wavelength radiation back into space. The greater weight of the second mechanism means that, on balance, clouds have a cooling effect.

’Twomey effect’ boosts reflectivity
Latham’s proposal, previously put forward by himself and a number of other scientists, involves increasing the reflectivity, or “albedo”, of clouds lying about 1 km above the ocean’s surface. The idea relies on the “Twomey effect”, which says that increasing the concentration of water droplets within a cloud raises the overall surface area of the droplets and thereby enhances the cloud’s albedo. By spraying fine droplets of sea water into the air, the small particles of salt within each droplet act as new centres of condensation when they reach the clouds above, leading to a greater concentration of water droplets within each cloud.

Latham and co-workers, including wave-energy researcher Stephen Salter of Edinburgh University, claim that such spraying could increase the rate at which clouds reflect solar energy back into space by as much as 3.7 Wm-2. This is the extra power per unit area that scientists say will arrive at the Earth’s surface following a doubling of the concentration of atmospheric carbon dioxide compared to pre-industrial levels — 550 ppm vs 275 ppm (Phil. Trans. R. Soc. A DOI:10.1098/rsta.2008.0137).

Moscow's leaders propose playing God with the clouds
Thu, Dec 10, 2009

Scientists are cooking up a plan to cut the cost of tackling snowbound streets – by clearing clouds from the skies, writes MEGAN K STACK in Moscow

IN THE snow-hushed woods on Moscow’s northern edge, scientists are decades deep into research on bending the weather to their will.

They’ve been at it since Soviet dictator Joseph Stalin paused long enough in the throes of the second World War to found an observatory dedicated to tampering with climatic inconveniences.

Since then, they’ve melted away fog, dissipated the radioactive fallout from Chernobyl and called down rains fierce enough to drown unborn locusts threatening the distant northeastern grasslands.

Now they’re poised to battle the most inevitable and emblematic force of Russian winter: the snow.

Moscow’s government, led by long-reigning mayor Yuri Luzhkov, has indicated that clearing the capital’s streets of snow is too expensive. Instead, the city is weighing up a plan to seed the clouds with liquid nitrogen or dry ice to keep heavy snow from falling inside its limits.

Word of the proposal has sent a shudder through Moscow just as the first dark, snowy days have fallen on the capital. It has also piqued the surrounding region, which would receive the brunt of the displaced snowfall, and has raised concerns among ecologists.

“I was very surprised, because [the mayor] never even asked us,” says Alexei Yablokov, who sits on the mayor’s ecological council and has concerns about the proposal, including the environmental effects and pressure on surrounding villages. “We never discussed it at all.”

The city government says it hasn’t reached a decision. But scientists at the Central Aerological Observatory say they are deep into negotiations with city authorities and expect the cloud-seeding plan to go forward.

The city has hit upon a splendid idea, the scientists say. Labouring against the uncomfortable sense that their observatory’s import has waned since its Soviet heyday, they are eager to unleash their many and various technologies.

They already seed the clouds for political effect, clearing the skies over Moscow twice a year to ensure sun-drenched celebrations of patriotic holidays. In Russia, nobody rains on the parade – because the Russian government doesn’t allow it.

“Victory Day is the most sacred holiday for us,” says Bagrat Danilian, deputy chief of cloud-seeding at the observatory. “When veterans go out to celebrate in Moscow, we create good weather for them.” All it takes, he says, is sacks of cement – 500 grade, to be precise.

Drop the powder down into the clouds, and they vanish.

Soviet scientists learned how to disperse clouds by accident 40 years ago: they had flown overhead and dropped powdered blue paint into the clouds to tag them for observation. Instead, the powder melted the clouds away.

A dark-haired, solid man with a quick grin, Danilian was born to an Armenian family in Soviet Georgia and studied physics at Tbilisi State University. He moved to Moscow in 1979 to work for the observatory and has been here ever since.

In Soviet times, when Danilian was younger and funding more plentiful, he was sent off to Vietnam, Cuba and Syria to study the clouds. He has flown into hurricanes; bounced through airstreams like a ping-pong ball; and survived lightning strikes on turbo-prop planes.

“You won’t find a more interesting profession,” he enthuses. “You can’t compare it with anything. You just float on your own adrenaline.”

There is something almost godlike about interfering in the weather. It was a need to rationalise the whims of storm, heat and climate that inspired the notion of deities in ancient times, and there is still an inherent sense of helplessness before nature’s force.

Russian cloud-seeding, however, is done in moderation, the scientists insist.

“You shouldn’t overstep the threshold over which the weather would change globally,” Danilian says. “We’re trying to look for that threshold in a very careful way.” Sometimes, despite their efforts, nature wins. And, in one instance last year, gravity.

As the Russian airforce toiled to chase the clouds out of town for last year’s independence day celebrations, a clump of cement tumbled to earth instead of dissipating into the clouds. It crashed through the roof of a house on the city’s outskirts.

Rather than accept the $2,000 (€1,400) compensation offered by the military, the homeowner huffed to reporters that she would file a suit for “moral suffering”.

It’s unlikely that Muscovites would agree to forgo snow altogether. During the long, dark months of Russian winter, the flicker of clean flakes against the sky is one of the few recurrent graces, creating a vast playground for children and briefly coating the drab winter days.

But Luzhkov is prepared to choke off any particularly massive snowfalls, which usually unleash battalions of snow ploughs, flanked by armies of workers hoisting ice picks and shovels. The city government believes it can save more than $13 million (€8.8 million) with cloud-seeding.

“In the movies, the snow looks very beautiful with St Basil’s Cathedral in the background,” Azarov, the senior scientist, says. “But this snow costs a pretty penny to Moscow authorities.”
http://www.irishtimes.com/newspaper/wor ... 24690.html
... Physicists have discovered that firing short laser bursts into the air can trigger the formation of water droplets. The breakthrough technique could help stimulate rainfall in the future.

Scientist Jerome Kasparian and his team from the University of Geneva wanted to find a more environmentally friendly alternative to cloud seeding. This 50-year-old process attempts to artificially induce showers.

Rockets carrying silver iodide particles are scattered in the sky. The particles act as 'condensation nuclei' around which water drops can form.

Dr Kasparian said cloud seeding is not an efficient method despite decades of development.

He added: 'There are also worries about how safe adding silver iodide particles into the air is for the environment.'

Read more: http://www.dailymail.co.uk/sciencetech/ ... z0mxFyFBq5

There are probably other rain-making tales out there, some not so scientific!
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Pollution levels reached a new record high for a third day in a row in Singapore, as smoky haze from fires in Indonesia shrouded the city state.

The Pollutant Standards Index (PSI) hit 401 at 12:00 on Friday (04:00 GMT) - the highest in the country's history.
The haze is also affecting Malaysia, with another 100 schools closed in the south of the country. ...

Singaporean Prime Minister Lee Hsieng Loong warned on Thursday that the haze could remain in place for weeks. ...

A PSI reading above 300 is defined as "hazardous", while Singapore government guidelines say a PSI reading of above 400 over 24 hours "may be life threatening to ill and elderly persons". ...

The fires are caused by illegal slash-and-burn land clearance in Sumatra, to the west of Singapore. ...

Indonesia says two helicopters with cloud seeding equipment were deployed early on Friday to try and create artificial rain to put out the fire, AFP reported.

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... The notion that we can alter the weather dates from the 19th century. Then, the belching factories of the Industrial Revolution caused profound changes in weather, creating darker skies over areas with a high density of factories and increasing rainfall.

Meteorologists of that era noted that public holidays tended to be sunnier and drier than working days, while during the First World War soldiers soon learned that a really big artillery barrage could trigger a thunderstorm

But it wasn’t until the 1940s that concerted attempts were made to change the weather. This was an era of incredible technological progress and innovation when there seemed to be no limits to what mankind could achieve. New jet aircraft were breaking the sound barrier, and scientists were making atomic weapons capable of destroying civilisation.

The logical next step, according to the US physicist John von Neumann, was to take control of the skies – whoever did so, he said, would control the world.

Another American, atmospheric scientist Vincent Schaefer, is credited with the first ''cloud-seeding’’ attempts. This involves spraying tiny crystals of substances such as silver iodide or frozen carbon dioxide into the air, using rockets or cannons from the ground or sprayed directly into the clouds from aircraft. The aim is to give nature a helping hand or hinder it.

Natural raindrops are created when water vapour in a cloud forms a droplet around ''condensation nuclei’’ – minute dust particles in the air. (It was the soot from those belching Victorian factories acting as condensation nuclei that generated those downpours.)

Cloud-seeding remains the basis of most weather-modification programmes. It is supposed to either create rain (as described above), or to prevent it by ''super-seeding’’ the cloud so that instead of raindrops, a mist of water droplets too light to fall is formed. An additional refinement would be to seed a cloud in one place, hoping that it ''dumps’’ its water vapour as rain before it gets a chance to do so over the place you want to stay dry.

Since the 1950s, the Americans and Russians have used cloud-seeding techniques to improve irrigation in arid regions, the dustbowl states of the Midwest for example – and, in the case of the latter, to guarantee blue skies over Moscow during the annual May Day parades. At the height of the Cold War, both sides enthusiastically embraced the technology as a possible weapon – knowing that a severe drought or series of storms could cause as much damage to a nation as a bombing campaign. The Americans later used cloud-seeding during the Vietnam War, hoping to trigger torrential downpours to make life unbearable for North Vietnamese troops in the jungles.

China, too, is a fan of weather-modification. More than a thousand rockets laden with iodide crystals were fired into the skies over Beijing ahead of the 2008 Olympic opening ceremony to ensure clear skies and no rain.

Only yesterday Indonesia’s national disaster agency deployed two helicopters to create rain to fight raging fires across hundreds of acres of carbon-rich peatland that have led to choking levels of dangerous smog in Singapore. “Hopefully, we will be able to create artificial rain,” said spokesman Sutopo Purwo Nugroho. ...

Worse than it not working, some say, is the fact that attempts to make it rain or stop raining could be dangerous. Rumours persist that the devastating floods which nearly washed away the town of Lynmouth in Devon in August 1952 were caused by secret cloud-seeding experiments by the RAF. A BBC documentary on the tragedy, which cost 34 lives, claimed that some residents had smelt sulphur in the air before the flash-flood.

For what it is worth, I have never met a serious meteorologist who believes that cloud-seeding has done more than perhaps trigger the occasional shower, and perhaps not even that. According to Helen Chivers of the Met Office, no form of weather modification is practised in this country. ''The UK is in a part of the world that sees mobile weather – weather which is driven by the jet stream and changes quickly – so, any attempt at modification would be pointless.”

She’s right. We are a nation occupying a northerly archipelago on the edge of a large ocean, after all. We should remember that there is no such thing as bad weather, only the wrong clothes. 8)

http://www.telegraph.co.uk/topics/weath ... shine.html
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A conspiracy theory has circulated that the [Lynmouth] flood was caused by secret cloud seeding experiments carried out by the Royal Air Force (RAF).[5][6]

The theory was fuelled by a 2001 BBC Radio 4 documentary, suggesting that the events of 1952 were connected to Project Cumulus. The programme alleged that "the infamous Lynmouth flood disaster came only days after RAF rain-making experiments over southern England", and that secret experiments were causing heavy rainfall.[7] According to the programme, "classified documents on the trials that Project Cumulus contributed to the conditions that caused this flood have gone missing."[7] A few days before the disaster a seeding experiment was carried out over southern England. Alan Yates, an aeronautical engineer and glider pilot who was working with the operation, sprayed salt in the air and was "elated" to learn of a heavy rainfall in Staines shortly after.

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May as well lob this in here: :twisted:

A conspiracy theory has circulated that the [Lynmouth] flood was caused by secret cloud seeding experiments carried out by the Royal Air Force (RAF).[5][6]

The theory was fuelled by a 2001 BBC Radio 4 documentary, suggesting that the events of 1952 were connected to Project Cumulus. The programme alleged that "the infamous Lynmouth flood disaster came only days after RAF rain-making experiments over southern England", and that secret experiments were causing heavy rainfall.[7] According to the programme, "classified documents on the trials that Project Cumulus contributed to the conditions that caused this flood have gone missing."[7] A few days before the disaster a seeding experiment was carried out over southern England. Alan Yates, an aeronautical engineer and glider pilot who was working with the operation, sprayed salt in the air and was "elated" to learn of a heavy rainfall in Staines shortly after.


So it's all Kate Bush's fault in that case .. we've solved it then .. I'm off to make my sandwich.

On this occasion it's to stop rain.

Indonesian authorities are turning to the technique of cloud seeding to try to stop more rain falling in the flood-hit capital Jakarta.

Planes have been sent to inject chemicals into clouds in an effort to alter precipitation. Jakarta and surrounding districts have struggled to cope since a storm on New Year's Eve left large areas underwater. At least 43 people are known to have died, with some 192,000 evacuated, and more rain is expected.

According to Reuters news agency, two planes have been sent up to shoot salt flares into the clouds, which will hopefully make them break before they reach the Jakarta region.

"All clouds moving towards the Greater Jakarta area, which are estimated to lead to precipitation there, will be shot with NaCl (sodium chloride) material," Indonesia's technology agency BPPT explained in a statement.

That's awful - is there anywhere not afflicted by a natural disaster recently? It's a pity they can't move the clouds to Australia.
The topic of cloud seeding has been much on my mind of late, especially as it relates to the Australian Bushfires. I have a number of old friends in danger in NSW and Victoria. Apparently nature uses bacteria to create rainfall (link), and maybe that is the key to getting cloud seeding to work reliably?
Interesting article in the FT this month suggests this is pure pseudoscience, and seeding doesn't work. Also, if it does, it's only moving rain from one region to another, not creating new rain.
Here's a rare mention of cloud seeding in the mainstream news. Putin ordered a fleet of Russian aircraft to "spike" the clouds around Moscow to prevent rain showers spoiling the annual (WW2) Victory Day parade. Either the rain threat was overestimated or the chemical spiking worked.
Putin had ordered rain clouds to be spiked ahead of today’s vast commemoration - to stop a downpour ruining his parade.

A fleet of Antonov-26 aircraft were deployed to ‘spike’ clouds with a chemical cocktail of weather-changing silver iodide, liquid nitrogen and dry ice, a Soviet technology developed in the Cold War which often drenches villages in Moscow region.
FULL STORY (About the Parade): https://www.thesun.ie/news/world-news/6967416/putin-vows-to-protect-russia-at-victory-day/
That's the thing, good weather might have happened anyway. You'd need to spike clouds and not spike clouds on the same day and in the same location to be sure. Which is impossible.
Try Googling weather modification company, lots of company's buggering about
with the weather as well as the usual suspects, he that controls the weather controls
the world, they have messed about with it for years I don't think anyone as the slightest
idea what the natural weather is really like.
Not that it will stop them blaming someone else and slapping a big tax on them.
I dunno, I'm reminded of Sean Connery the OTHER Avengers movie!
Kurt Vonnegut's brother, Bernard Vonnegut, was important in the early development of cloud seeding in the 1940s and 50's. Bernard Vonnegut wanted to develop this technique as a peaceful method for assisting crop growth; the US industrial-military complex wanted to develop a 'weather-bomb', that could be used in the coming war against the Soviets.

Scientists with similarly conflicted goals turn up regularly in Kurt Vonnegut's novels, based, it is said, on his brother Bernard.
China rules the skies.

Chinese weather authorities successfully controlled the weather ahead of a major political celebration earlier this year, according to a Beijing university study.

On 1 July the Chinese Communist party marked its centenary with major celebrations including tens of thousands of people at a ceremony in Tiananmen Square, and a research paper from Tsinghua University has said an extensive cloud-seeding operation in the hours prior ensured clear skies and low air pollution.

The Chinese government has been an enthusiastic proponent of cloud-seeding technology, spending billions of dollars on efforts to manipulate the weather to protect agricultural regions or improve significant events including the 2008 Olympics.

Cloud-seeding is a weather modification technique, which sees the adding of chemicals like small particles of silver iodide, to clouds, causing water droplets to cluster around them and increasing the chance of precipitation.

The Tsinghua study’s reported findings add to a small but growing body of scientific evidence around the success of the technology. Other countries have also invested in cloud seeding technology, but China has invested billions despite questions over the degree of its effectiveness, and debate about whether manipulating the weather in one area could disrupt weather systems elsewhere.

Read a article a wile ago that it was cheaper to change the weather so it didn’t snow in Moscow than pay for the snow to be moved I have thought for a time that the odd weather we get is due more to it being messed with than the things that get blamed or even weather wars going on
Now we have cloud seeding conspiracy theories emerging in Australia in response to recent torrential rainfalls.
Torrential rains hit Australia as conspiracy theorists blame aviation company for floods

AN AUSTRALIAN AVIATION company says it has received more than 100 threats following an online conspiracy theory that its pilots unleashed a flooding disaster by cloud seeding.

Conspiracy theorists spread the false claims after weeks of torrential rains led to deadly east coast floods over the past two months, engulfing homes and sweeping cars from the roads.

Posts shared online alleged aerial survey pilots from Handel Aviation caused a second deluge in the flood-ravaged New South Wales town of Lismore on March 31 by cloud seeding — dispersing a substance into the clouds to prompt rain. ...

Handel Aviation operator Mark Handel told AFP that the company does not seed clouds.

The flight was collecting images for aerial maps provided to Australian mapping company, NearMap, he said. ...
FULL STORY: https://www.thejournal.ie/cloud-seeding-australia-rains-5733332-Apr2022/
Try Googling weather modification company, lots of company's buggering about
with the weather as well as the usual suspects, he that controls the weather controls
the world, they have messed about with it for years I don't think anyone as the slightest
idea what the natural weather is really like.
Not that it will stop them blaming someone else and slapping a big tax on them.
I've seen quite a few royal events/war anniversaries etc over the last few years and it does seem to usually be a lovely sunny day, no matter the time of year. For the more senior royals/events anyway.