Yes, we can make it rain. But that won’t solve the drought.


Grappling with its worst heat wave on record, Chinese authorities are scrambling to dramatically expand the country’s “cloud seeding” programs – a controversial method of stimulating clouds to make them rain.

This is naturally a time for desperate measures. China’s mighty Yangtze River has slowed to a trickle in some stretches, destabilizing the country’s hydropower generation and leaving hundreds of thousands of people without clean water. But it’s also time to set the record straight on cloud seeding – a practice that is growing rapidly in the water-scarce American West.

Yes, forcing clouds to form rain and snow has actually been proven to increase precipitation by up to 15% in some areas, and the emerging industry of cloud seeding by the private sector deserves more research and investment in a climate-stressed world. But cloud seeding is not a silver bullet to a drought crisis: the process of injecting tiny particles or chemical vapors into clouds to trigger rain is not a guaranteed solution to Requirement. At most, it should be seen as a supporting measure in comprehensive, long-term water management plans.

A few years ago, I traveled to Maharashtra, India, to observe a cloud seeding program up close from the window of a turboprop flying through the belly of a monsoon cloud. Here’s what I learned: cloud seeding is a promising technology — and one that has seen rapid progress in recent years — but there are a lot of “ifs.”

Dan Breed, a scientist who led cloud seeding research at the National Center for Atmospheric Research, explains the challenge this way: “There is little dispute that if you get the seeding material inside clouds, it can increase precipitation. The question is, by how much, and do you have the right cloud conditions, and will those clouds be there when you need them? »

China has by far the largest cloud seeding program in the world. It is also common practice in countries ranging from Thailand and Australia to the United Arab Emirates and the United States. Over the past two years, Colorado, Idaho, Utah, Wyoming and California have expanded cloud seeding operations, including to build up snowpack on the Sierra Nevada mountains that merge into the tanks.

There are two types of cloud seeding. In India, I witnessed “hygroscopic” or water-attracting seeding, the method often practiced in China, in which rockets or flares on the wing of an aircraft blast billions of particles of superfine salt in a cloud. Water molecules are attracted to the salt, so they bind to the particles and turn into raindrops.

“Orographic” cloud seeding in cold weather has more proven results. Flares eject tiny flakes of silver iodide into the heart of clouds reaching 60,000 feet. Silver iodide has a molecular structure similar to ice. As the particles drift through the clouds, the water coats them like ice and snowflakes form. A recent study by the Center for Atmospheric Research used radar and weather modeling to definitively show that orographic seeding can increase snowfall.

In the decades since cloud seeding was introduced, fears that it could be toxic to the environment have dissipated. Sodium chloride is simply pulverized table salt, harmless to the environment, and can be washed from land below by additional rainfall. And while silver iodide in large concentrations can be harmful, the amounts found in the snowpack after cloud seeding are often undetectable. Studies have shown that there was no more silver iodide in snow and soil samples in cloud seeded areas than there was before the campaigns – probably because the additional rains have purged the system.

Technology is improving steadily. Most notably, scientists now have computer models to simulate the effects of silver iodide seeding, allowing scientists to identify the most opportune locations for weather enhancement. As processing power improves, these models will also increase.

But no matter how sophisticated the modeling, the method is unlikely to be useful in a drought emergency – mainly because you need storm clouds for successful seeding, and droughts by nature offer little. When storms occur, hot weather seeding needs a particular form of moisture-rich clouds to achieve substantial increases in precipitation. Even negligible increases might be worth the effort in a water-scarce region, but it won’t be a panacea.

In the long term, the most effective use of cloud seeding is to practice it continuously, seeding in wet and dry years to supply reservoirs and moisten the soil.

Here’s what investors need to know: Cloud seeding is a niche industry growing far beyond the United States and China. The United Arab Emirates, for example, recently built a facility producing hundreds of flares per week. Demand is likely to only increase: in India, for example, a recent government study predicts that demand for water in 2030 will be more than double the country’s available supply. In the United States, major drought events are expected to triple by mid-century.

But lawmakers and investors should proceed with caution: They can look to the Colorado River Basin Drought Contingency Plan for a good example of how cloud seeding can be integrated into a strategy. broader drought management that includes rigorous consumer efficiency programs, water infrastructure and rivers. – improvements in management and new sources of drought-proof water supply such as recycled wastewater. But mankind has been altering natural systems for centuries, redirecting rivers with dams and reshaping landscapes with ancient and modern irrigation canals. At this point, our reality is stark: we need every potential solution on the table, and that means cautiously using controversial technologies to tackle the much more blatant hubris of man-made climate change.

More other writers at Bloomberg Opinion:

Drought in Europe could have a long afterlife: Stephen Mihm

Iowa water crisis offers glimpse of future: Adam Minter

The Future of the American West is Central Oregon: Francis Wilkinson

This column does not necessarily reflect the opinion of the Editorial Board or of Bloomberg LP and its owners.

Amanda Little is a Bloomberg Opinion columnist covering agriculture and climate. She’s a professor of journalism and science writing at Vanderbilt University and author of “The Fate of Food: What We’ll Eat in a Bigger, Hotter, Smarter World.”

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