New research has shown that cloud-seeding, the process through which precipitation is controlled by dispersing chemicals into clouds, may not actually have any real effect.
According to scientists at Tel Aviv University it seems that, despite hope that chemicals such as frozen carbon dioxide and silver iodide would be able to stimulate rain fall in desired areas, any apparent successes can be explained by natural phenomena.
The expensive process of cloud-seeding is practised across the world, even being employed at the 2008 Beijing Olympics, so it will be disappointing news for the countries which have invested heavily in the technology. According to a World Meteorlogical Organisation report there are 80 such projects currently taking place.
Prof Pinhas Alpert, Prof Zev Levin and Dr Noam Halfon of Tel Aviv University’s Department of Geophysics and Planetary Sciences, pored over fifty years of cloud-seeding data, predominantly in an area north of Israel in the Sea of Galilee, noting the amount of rainfall over extended periods of time.
The scientists also compared the data with periods when cloud-seeding was not being attempted and with nearby areas where seeding did not take place.
“By comparing rainfall statistics with periods of seeding, we were able to show that increments of rainfall happened by chance. For the first time, we were able to explain the increases in rainfall through changing weather patterns,” said Prof Alpert.
Professor Alpert noted that a specific period of six years where there was significantly increased rainfall – formerly thought to be conclusive proof of the method succeeding – could in fact be attributed to natural causes.
The scientists managed to prove that the rainfall was actually caused by cyclones which commonly caused increased rainfall in mountainous areas. The rainfall was very similar to that of similarly increased precipitation in the Judean Mountains region where cloud-seeding had never taken place.
It was concluded that increased rainfall was in fact attributed to natural weather conditions, though the scientists did comment that in the case of orographic clouds, which form briefly having condensed over mountains, it may be possible to accelerate the formation of precipitation.