Washington, April 23 : With advanced technology, the practice of cloud seeding to create rain, mitigate hail or even quell hurricanes is now on the road from science fiction to fact.
According to a report in Discovery News, doppler radar, advanced weather satellites and sophisticated weather models, combined with a lot of accidental, human-caused weather modification, make it finally possible to assess whether humans are having any effect on clouds.
"There was a lot of excitement in the 1950s," said Roelof Bruintjes of the National Center for Atmospheric Research.
But without any information about what was happening inside the clouds, it was impossible to tell if a shot of silver iodide into a cloud was really forming rain, or not, he added.
"What's more, a cloud-seeding technique that might appear to work one day might not work on another day, from season to season, or from place to place," said Bruintjes. his made it very hard to move ahead with any genuine science of weather modification.
Now, however, it's possible to see changes on the order of 10 to 15 percent in rain or snowfall when silver iodide is used to stimulate rain formation or when special salts are used to increase the size of existing raindrops.
"These are the only two cloud-seeding techniques with any scientific backing," said Bruintjes.
"It's also getting easier to see how air pollution particles, called aerosols, and urban heat are modifying the weather," said Joe Golden, senior researcher for the National Oceanic and Atmospheric Administration's Earth System Science Laboratory.
"This pollution in regions that depend on uplift of air (over mountains) for precipitation has caused a systematic decrease in snow packs," he added.
According to Golden, "These are two examples of human-caused effects on weather that concern us."
So much so that he and other scientists are beginning to collaborate with the US Department of Homeland Security to see if there may be ways to modify weather - especially hurricanes - that decrease hazards.
"Now we have much better observing tools for looking at hurricanes," said Golden.
On the other hand, there is little hope that China's efforts to keep rain from falling on the Olympics will succeed, according to scientists.
"China has spent 100 million dollars and employed 30,000 people in weather modification projects, but they are using old techniques from the 1960s and 1970s and have no way of evaluating whether their efforts are working," said Bruintjes.