Scientists are attempting to control the weather by using lasers to create clouds, induce rain and even trigger lightning.
Experts from around the world are to gather at the World Meteorological Organisation next month to discuss how powerful laser pulses can be used to generate changes in the atmosphere that influence the weather.
Their experiments have shown that intense pulses of light can cause ice to form and water to condense, leading to the formation of clouds.
The scientists have now begun testing their equipment outside for the first time with extremely short pulses of laser light were fired into the sky.
Researchers have also proved that lightning discharges can be triggered and channelled through the air using laser pulses.
They hope the technology could allow lightning during thunderstorms to be guided away from sensitive buildings such as power plants or airportsIt could also be used to manipulate the weather by creating clouds and triggering rainfall ahead of major public events.
Professor Jean-Pierre Wolf and Dr Jerome Kasparian, both biophotonics experts at the University of Geneva, have now organised a conference at the WMO next month in an attempt to find ways of speeding up research on the topic.
They said: “Ultra-short lasers launched into the atmosphere have emerged as a promising prospective tool for weather modulation and climate studies.
“Such prospects include lightning control and laser-assisted condensation.”
There is a long history of attempts by scientists to control the weather, including using techniques such as cloud seeding.
This involves spraying small particles and chemicals into the air to induce water vapour to condense into clouds.
In the 1960s the United States experimented with using silver iodide in an attempt to weaken hurricanes before they made landfall.
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The USSR was also claimed to have flown cloud seeding missions in an attempt to create rain clouds to protect Moscow from radioactive fallout from the Chernobyl nuclear disaster.
More recently the Russian Air force has also been reported to have used bags of cement to seed clouds.
Before the 2008 Olympic Games in Beijing, the Chinese authorities used aircraft and rockets to release chemicals into the atmosphere.
Other countries have been reported to be experimenting with cloud seeding to prevent flooding or smog.
However, Professor Wolf, Dr Kasparian and their colleagues believe that lasers could provide an easier and more controllable method of changing the weather.
They began studying lasers for their use as a way of monitoring changes in the air and detecting aerosols high in the atmosphere.
Experiments using varying pulses of near infra-red laser light and ultraviolet lasers have, however, shown that they cause water to condense.
They have subsequently found the lasers induce tiny ice crystals to form, which are a crucial step in the formation of clouds and eventual rainfall.
In new research published in the Proceedings of the National Academy of Sciences, Professor Wolf said the laser beams create plasma channels in the air that caused ice to form.
He said: “Under the conditions of a typical storm cloud, in which ice and supercooled water coexist, no direct influence of the plasma channels on ice formation or precipitation processes could be detected.
“Under conditions typical for thin cirrus ice clouds, however, the plasma channels induced a surprisingly strong effect of ice multiplication.
“Within a few minutes, the laser action led to a strong enhancement of the total ice particle number density in the chamber by up to a factor of 100, even though only a 10−9 fraction of the chamber volume was exposed to the plasma channels.
“The newly formed ice particles quickly reduced the water vapour pressure to ice saturation, thereby increasing the cloud optical thickness by up to three orders of magnitude.”
Another paper in the journal of Applied Physics Letters also indicated that ultraviolet lasers were far more efficient at producing condensation.
In March this year, Professor Wolf and his team also tested a high powered 100 terawatt laser in the field by firing it into the sky above a research centre in frascati, near Rome in Italy.
He said: “The aim of the experiment is to investigate the scaling up of the water condensation experiments already demonstrated at lower intensities.”
Professor Jean-Claude Diels, from the department of Physics at the University of New Mexico in Albuquerque, will talk at the conference on how laser pulses can be used to guide lightning.
Previous attempts to guide lighting have used rockets towing wires as they were fired into storm clouds.
Laboratory tests by Professor Diels, however, have shown that electrical discharges can be guided along the path of a laser beam.
Their work has raised hopes that pulses of light can be used to steer lightning strikes away from buildings, vehicles and areas where they would be dangerous to humans.
Professor Diels said: “We are investigating a scaling up of these experiments across larger gaps. An application being investigated is the triggering and guiding of lightning.”
