Seed capital

"Perhaps we overdid it"

There’ll be no raining on their parade next week, if Beijing’s rocket men have their way.

The city’s weathermen would normally estimate a 30% chance of drizzle at this time of year. But few expect that participants at the National Day celebrations are going to get wet. The government will just not permit it.

There were similar assurances for the Olympics last year, when dry skies were guaranteed too. More than a thousand rockets were launched from 21 sites in and around the city, to have the rain fall to order. Umbrella salesmen at the Games venues took the month off.

Chinese research into weather control dates back to 1958, under the Weather Modification Department. The division now employs at least 35,000 people, including the anti-aircraft gunners who propel silver iodide pellets into the clouds.

The strategy: to trigger a deluge now so as to ensure that it does not spoil a good day out later.

However, the main purpose of cloud seeding is to generate rain for drought-hit areas. The dry northern provinces are probably the keenest rainmakers. Officials in Beijing have previously told the Asia Times that water levels in the city’s basins have been increased by 13% due to seeding. The China Daily also reported last week that thousands of rain rockets have been fired in Henan province since August, where more than a million locals are struggling with low water supply.

Under the ‘static’ method of cloud seeding, silver iodide is fired skywards to create ice crystal nuclei around which water droplets can attach. When the droplet becomes large enough, it will fall as rain.

In the ‘dynamic’ technique, the seeders try to develop vertical air currents, to encourage water to move through clouds.

But in both cases the seeding is thought to increase the number of nuclei available, and thus take advantage of cloud moisture to form raindrops. That is the theory, and many countries have experimented with rainmaking. China already spends $100 million annually on it.

But some scientists question whether cloud seeding works as promised. Rival studies offer apparently contrary results; in 2003, the Associated Press reported that the United States National Academy of Sciences saw no “convincing” evidence that weather modification had been successful. But the American Meteorological Society has claimed that some studies show a 10% increase in rain volume.

The problem is that it is difficult to assess if it would have rained in a given area without the use of cloud seeding (or if would it have rained less).

Success also heavily depends on environmental conditions like temperature and cloud composition.

Perhaps this is the key point. The rainmakers are not actually creating clouds. But they are trying to make them more efficient in producing rain (or snow, in the case of ski resorts).

So is it worth the money? Supporters argue that it’s cheaper than other irrigation projects. But there are the wider questions about disturbing nature’s balance, especially if cloud seeding creates rain in one region that would more usually fall in another.

There is also the argument that seeding is a distraction from much bigger issues in our environmental future. If regions are experiencing drought due to climate change, wouldn’t resources be better spent tackling the causes of global warming? In this context, cloud seeding looks like more like a fig leaf than a fundamental solution.

And in China there are even more immediate dangers. The erratic firing of rockets has damaged property and even killed a person in 2006.

That’s the type of downpour that would have most people scurrying indoors.

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