China says its scientists make enough rain to fill the Yellow River; Moscow claims credit for sunshine for Red Square parades — but confidence in other nations that humans can alter the weather has almost dried up.

If it worked reliably, the use of aircraft and rockets to spread tiny chemical particles into the sky to ”seed” or disperse clouds could be the answer to famine, drought, desertification, even global warming.

However, lack of proof that it works means that funding by many governments has fallen sharply, after millions of dollars were spent on teasing rain from clouds in arid regions of West Africa, or on research into trying to prevent hurricanes.

”There used to be big optimism about weather modification in the 1960s and 1970s,” said Slobodan Nickovic, the World Meteorological Organisation”s expert on changing the weather.

”But so far fog dispersal…is the only activity where we have a high level of confidence in the technology,” he said.

Dispersing fog is useful, especially around airports, but hardly a solution to humanity”s wider woes with the weather.

A 2005 WMO report expressed confidence that human use of chemicals could affect cloud formation but said there was only ”medium” or ”low” confidence that the changes lead to significant changes in rains, hail or snow on the ground.

It said the ”unsatisfactory status” of weather research reflected a lack of understanding of the complexities of clouds.

Rain dancers can sometimes claim credit for a downpour, even when clouds were about to burst.

”Most questions about weather modification are still open,” Nickovic said, adding that more research was needed.

Some countries disagree.

Russia claimed credit last year for drying up rains that had threatened a Moscow parade celebrating the end of World War Two, attended by President George W Bush and other world leaders.

Eleven planes seeded clouds with chemical dispersal agents under techniques Moscow says it has perfected over decades and that it says were used to keep the 1980 Moscow Olympics sunny.