India’s making a big, expensive stab at determining once-and-for-all whether man can make it rain. (No, not in the figurative sense.) Color us a little skeptical; we’ve always thought that positive cloud-seeding results were often due more to luck than the effects of sprinkled silver iodide. (For the umpteenth time, people, correlation is not causation.) And this recent Scientific American interview with an American cloud-seeding expert doesn’t do much to allay our suspicions. Note the man’s cautious hedging throughout:
What are the best results you can hope for with cloud seeding?
It depends on where you are, and the reasoning behind it. If you’re trying to increase rain or snowfall for the water supply, a 10 percent addition could do a lot. If you had a large basin like I work with, between 300,000 and 500,000 acre-feet, a 10 percent increase would equal 30,000 to 50,000 more acre-feet of water. If you can do that, it’s very economically sound.Can you attribute any one storm to cloud seeding?
Generally, you can’t look at one individual storm. Would it have snowed anyway? You don’t know. NCAR (the National Center for Atmospheric Research in Boulder, Colo.) is in Wyoming studying several seasons in comparison, where you seed one place and withhold another. Attributing one storm to seeding is very difficult unless the cloud system is incredibly simple, like fog that has no chance of precipitation. If you see snowfall then, that’s pretty demonstrative evidence that you succeeded.
Still, Malaysia evidently buys into the technology, as an anti-wildfire measure. Best of luck to them.
Brian Moore // Jul 17, 2009 at 6:32 pm
It’s definitely standard procedure in China, as the SA article notes. I remember reading they tried something to ensure sunny weather for the Olympics too — something about trying to make it rain with seeds (shot out of old 88mm artillery guns) so that all the precipitation would have fallen before the games began.
Brendan I. Koerner // Jul 17, 2009 at 7:23 pm
@Brian Moore: Yeah, I remember that pre-Olympics tale.
The thing about cloud seeding is that it’s impossible to do a controlled study. Weather is unique to a specific geographic location and time, so it’s not like you can send up “placebos,” then accurately measure how those results compare with actual silver-iodide dispersal.
My gut tells me that sometimes folks get lucky, and thus become evangelists of the technology. But given how little we seem to know about how weather works, I’m highly skeptical that we’re able to control it even a little bit.