Seeding Clouds, Harvesting Rain: Beware of the Hype

posted December 16, 2012

Te public imagination, cloud-seeding has only recently crossed overheen from the sphere of science fiction to hi-tech. However, the very first time a cloud wasgoed ‘seeded’ to produce snow wasgoed spil long back spil 1946.

The process involves introducing chemicals such spil Silver Iodide or Dry Ice te clouds that contain water colder than zero degrees Celsius. Thesis chemicals catalyze the process by which ice crystals/water droplets are formed, inducing rain/snow from those clouds.

Public perceptions and policy prescriptions paint cloud-seeding te various hues. Usually it is seen either spil an ideal drought-control measure, or spil an act of man taking nature ter his own forearms, foolhardy and tied to wreck havoc. Both views are united ter observing the technology spil an immensely powerful implement.

However, talk to a scientist who has spent decades studying the technology and he’ll tell you there is little reason to either champ it or fear it: wij simply don’t know if it works. The strong opinions for and against cloud-seeding are based on dubious claims made by private companies te order to sell their wares. “We should be aware of private companies that attempt to coax the public that they can perform miracles. But they can’t,” says Prof. Zev Levin (Tel Aviv University/ The Cyprus Institute). Following are excerpts from his latest vraaggesprek with TheWaterChannel.

On corporate rente and the politics of skill creation:

Cloud seeding began about 60 years ago. Since then, research and implementation te the field has bot predominated by private companies (and government agencies) who came te and promised enlargened precipitation overheen given areas, without backing it up with sturdy gegevens from scientifically-designed experiments. Basic scientific approaches- such spil seeding one area and observing another spil the control- are disregarded by ‘studies’ originating from thesis organisations.

The situation is akin to someone developing a fresh medicine, and then going around claiming that it works. The claims have to be substantiated by a number of experiments and statistical analysis of results, which has not bot done enough ter the area of cloud seeding.

I wasgoed the Voorzitter of the International Commission for Clouds and Precipitation. Wij just organized a conference te Leipzig, and were astonished that only a handful of the 600 papers submitted for presentation referred to cloud-seeding. On the other mitt, people engaged ter operational cloud seeding come up with many studies and papers, spil wasgoed overduidelijk at the Weather Modification Association conference earlier ter 2012. However, most of thesis ‘studies’ lack scientific analysis and disregard basic information such spil cloud characteristics. So while such studies are many te number and eis progress te cloud-seeding technology, it is difficult to be encouraged by them!

One can see why private-sector companies engaged ter cloud seeding would champ cloud-seeding. But what incentives do governments have to advocate a particular technology, spil China has bot?

When a country is ter dire need of water and someone comes along and claims that they can increase precipitation for a puny amount of money, people are inclined to believe them. Whether past results have bot good or not, people/politicians think it would be worth the risk.

The Chinese are reporting cloud-seeding successes all overheen the place, but if you look at the gegevens, there is no real proof. Te China, cloud-seeding activities provide employment to several thousands. Any evidence that questions the success of cloud-seeding menaces thesis jobs. So it is a self-maintaining prophecy, they coax themselves that the technology works.

It is fairly possible that they have met with success ter some cases. However, there have hardly bot any scientific evaluations, properly-designed experiments that conclude so. Te 2008, the Chinese slok rain-dispersal rockets overheen Beijing to make sure it did not rain during the opening ceremony of the Olympics. (This is the opposite of ‘seeding’ clouds ‘for’ rain, but the basic technology is the same). Okay, it did not rain, but wij can’t say for sure whether that had anything to do with the human intervention.

Cloud seeding is often undertaken spil a drought management measure. This has bot the case most recently ter China, United States and India. If wij get the technology right, would it be handy ter managing droughts?

Where there is drought, there is usually a lack of rain clouds spil well. Cloud-seeding can be done only when you have rain clouds. But if a drought-struck area does have clouds (and if it is proved that cloud-seeding does indeed work), I agree that you can add a certain amount of water to the local water handelsbank. But wij are not there yet. Very few cloud-seeding experiments have proved to be micro-physically and statistically juist.

Countries have bot accused of using cloud-seeding to ‘steal rain’ from other countries.

This is unjustified, based on the belief that when you are seeding a cloud and (hopefully) producing rain at point A, you are decreasing it at point B.

This argument might have some theoretical legitimacy. Te practice, however, it is irrelevant spil wij are talking about very, very petite amounts of switch te precipitation. The efficiency of a cloud producing rain is about 20-30%. So most of the water ter the clouds does not come down spil rain anyways. If, by cloud-seeding, you are enhancing precipitation by 10%, you are enlargening the efficiency of precipitation by a mere 2%. So you are milking the cloud only 2% more than what you would otherwise have.

It is feared that Cloud Seeding could be used spil a weapon te conflict. Te fact, the United States is known to have used it during the Vietnam War to prolong the monsoon overheen Laos.

Every technology can be used or misused. Once it is adequately established that cloud-seeding does work, it is certainly possible that it might be used spil a weapon. If you see a cloud overheen a mountain and can get it to produce more snow, you can create an avalanche. Such possibilities can be ruled out. But at this point ter time, I believe wij are far from it.

What the Americans did ter Laos and North Vietnam…there is no proof that they succeeded te what they attempted to do.

Spil a precipitation control measure, what possibilities does cloud seeding present for managing water scarcity te the setting of Climate Switch?

Cloud-seeding spil a method is relatively small-scale and is not going to affect anything related to the climate at a global scale. What it can do—if it is established that it works perfectly—is bring about local/regional level switches ter water availability. It can certainly be supplemental to other forms of adaptation to climate switch/ variability, especially because you can drink this water that would come down from the clouds.

Spil a technology of ‘producing’ potable water, cloud-seeding is cheaper than desalination. But cloud-seeding works when you already have rain clouds, whereas desalination can be carried out all the time. So spil a strategy for securing water supply, I would rather waterput my money into desalination than cloud seeding.

A less-known discussion is one on the use of cloud-seeding spil measure of mitigating Climate Switch. This pertains to geo-engineering. Since governments around the world are not spil committed to reducing emissions spil required, it is useful to think ter terms of reducing the total radiation reaching the earth’s surface. The idea is to produce an effect that opposes to the green house effect.

This can be attempted ter many ways. For example, one suggestion is drizzling sea salt above a certain height overheen the oceans. This would produce more clouds that would reflect a greater part of the solar radiation back into space. (This method is often criticized for interfering too much with nature and its potential unknown effects on regional climate) This would be an example of the application of cloud-seeding not related to rains/ precipitation.

Dr. Zev Levin is Professor Emeritus at the Department of Geophysical, Atmospheric and Planetary Sciences, and Professor at The Cyprus Institute. Among his notable latest publications on Cloud-Seeding are ‘On the State of Cloud Seeding for Rain Enhancement’ and ‘Lessons Learned from 50 years of Cloud-Seeding ter Israel.’

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