How much can we really manipulate the weather?

Chinese scientists claim to be able to control the weather. But is so-called geoengineering more than wishful thinking? And, if so, should we be worried?

The unseasonal snow that fell on Beijing for 11 hours on Sunday was the earliest and heaviest there has been for years. It was also, China claims, man-made. By the end of last month, farmland in the already dry north of China was suffering badly due to drought. So on Saturday night China's meteorologists fired 186 explosive rockets loaded with chemicals to "seed" clouds and encourage snow to fall. "We won't miss any opportunity of artificial precipitation since Beijing is suffering from a lingering drought," Zhang Qiang, head of the Beijing Weather Modification Office, told state media.

The US has tinkered with such cloud seeding to increase water flow from the Sierra Nevada mountains in California since the 1950s, but there remains widespread scientific sniffiness in the west at such attempts at weather control. The chemicals fired into the sky, usually dry ice or silver iodide, are supposed to provide a surface for water vapour to form liquid rain. But there is little evidence that it works – after all, how do investigating scientists know it would not have rained anyway?

Such doubts have not stopped China claiming mastery over the clouds. Officials said the blue skies that brightened Beijing's parade to celebrate 60 years of communism last month were a result of the 18 cloud-seeding jets and 432 explosive rockets scrambled to empty the sky of rain beforehand. Last year, more than 1,000 rockets were fired to ensure a dry night for last year's Olympic opening ceremony.

"Only a handful of countries in the world could organise such large-scale, magic-like weather modification," Cui Lianqing, a senior meteorologist with the Chinese air force, told the Xinhua news agency after last month's parade.

Magic or not, there is growing interest in such attempts to deliberately steer the weather, and on a much larger scale. Next spring, a group of the world's leading experts on climate change will gather in California to plan how it could be done as a way to tackle global warming, and by whom. The ideas, some of which, similar to cloud-seeding, involve firing massive amounts of chemicals into the atmosphere, can sound far-fetched, but they are racing up the agenda as pessimism grows about the likely course of global warming.

For the more creative thinkers among you, here is a possible key to why chem trails have been going on and why they can't let on what we've been doing.

Unilateral geoengineering worries experts for two reasons. First, the massive side effects; what it could do to the world's rainfall, for example. Second, once started, geoengineering would probably have to be continued, as stopping could bring an abrupt change in climate. "One of the many dangers with unilateral geoengineering is that once a country starts, it becomes very hard to stop," Victor says. "Removing a warming mask, even if it is a flawed mask, would expose the planet to even more rapid and probably dangerous warming."

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Robock's new analysis still includes 17 reasons why geoengineering is a bad idea. Throwing sulphur into the atmosphere could slow down the world's water cycle and do more damage to rainfall patterns than the global warming it aims to prevent. And because techniques that focus on stopping sunlight do nothing to stop carbon dioxide pollution from cars, factories and power stations, they cannot address the looming disaster of ocean acidification. The surface of the world's ocean is slowly turning to acid as our extra carbon pollution dissolves in seawater. Coral reefs already appear doomed and many shellfish could follow. Altering the atmosphere could also weaken solar power and reverse years of work to close the hole in the ozone layer.

With such a catalogue of potential disasters waiting to unfold, there must be a law against geoengineering? The international rulebook is fuzzy on this issue. The only international framework that directly covers many geoengineering techniques, the 1976 Environmental Modification Convention, designed to stop nations at war from meddling with each other's weather, has never been tested. The 1982 UN Law of the Sea Convention and the 1967 Outer Space Treaty could be used to regulate activities and experiments in those shared spaces, but releases to the atmosphere are legally more problematic because nations have sovereignty over their own airspace.

via Can we manipulate the weather? | Environment | The Guardian.