Nevertheless, because weather is the epitome of a complex, emergent system, no analytical models or methodologies existed that produced data conclusively, proving that weather modification worked. In the United States, research funding died down and commercial weather modification efforts became hemmed in by stringent regulation. A 2003 report from the National Academy of Sciences concluded that despite more than 30 years of efforts, "there is still no convincing scientific proof of the efficacy of intentional weather modification efforts."
Still, according to William Cotton, a meteorologist at Colorado State University, "as far as the science of weather modification is concerned, the evidence that it works in certain situations is very compelling." The Chinese are certainly in no doubt: once they have demonstrated their capabilities to the rest of the world at the Olympics later this year, the party's central planners intend to expand their national weather modification program in 2010, turning the Weather Modification Office into a separate government ministry that will double the amount of rain-making and other weather engineering that China is now doing.