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It's been ages since I looked into cloud seeding, so maybe my knowledge is just incredibly out of date... but is there any high quality evidence that it works?

It's been ages since I looked into cloud seeding, so maybe my knowledge is just incredibly out of date... but is there any high quality evidence that it works? I mean, to be clear, working at the scale required for agriculture. By the same token if it does work, doesn't this open a potentially brutal avenue for hydrological warfare/competition? Edit: Great responses, I learned a lot, thanks!

earthscienceman 3y ago
I'm an atmospheric scientist who has written/contributed to papers on cloud microphysics, albeit in the Arctic. I have not directly researched cloud seeding but do have the background to understand the dynamics at play. The answer is, at agricultural scales, absolutely not. What I think is interesting though is that your comment on "hydrological warfare/competition" is extremely relevant. Geo-engineering is almost always a hack with "no free lunch" impacts. For cloud seeding specifically, there is only ever so much water vapor available in the atmosphere and the efficacy of seeding depends on the dynamics/microphysics at play in the region of interest. If there is a lack of the specific aerosols necessary for condensation and precipitation, cloud seeding has shown to be effective to the tune of 5-15% increase in precip in certain regions. Water vapor doesn't like to hang out available in the atmosphere in large quantities so squeezing it out by forcing precipitation via "seeding" isn't really a reasonable concept. But to the degree that you do succeed, you are extracting water vapor that would have been transported by the atmosphere to other neighboring regions. While there is little evidence that cloud seeding can be done at-scale, in a world where someone comes up with a novel+clever idea this would mean that the impacts on precipitation in other regions would be significant. Again, no free lunch. It's not a stretch to imagine turning that into a competitive advantage or using it as a warfare tactic. If there were large bands of moisture just waiting to fall out of the sky we would be living in a very different climate. Aerosols are far too common on earth. In fact, the Arctic is one of the only places seeding makes a lot of sense with supercooled water and a distinct lack of aerosols in the clean environment. But in my research I have yet to come across much agriculture up there much less agrarian societies ;)
- crznp 3y ago
  If we imagine that excess water from Wyoming is used to grow crops in California, it seems reasonable to assume that it would be less moisture/precipitation for Nebraska. But if it is used to grow wheat in Colorado (because the obligations to lower-basin states need to be met regardless and the increased moisture allows more diversions across the continental divide), then it probably ends up evaporating anyway or else in the Platte River. It wouldn't be stealing moisture from Nebraska, they might actually benefit from it. Geo-engineering might not have a free lunch, but it also isn't a zero-sum game.
galuvian 3y ago
Maybe and yes. It violates the Geneva Convention. But I’m sure there would be ways to ‘justify it’ if a country wanted to do so. I had expected that it was not economically viable for agriculture, but the article has one source claiming it is actually quite affordable, given current water prices in the west. A large portion of the article tries to give both sides a voice. https://en.m.wikipedia.org/wiki/Weather_warfare https://en.m.wikipedia.org/wiki/Weather_warfare
gnabgib 3y ago
Yep, in 2017[0]. Suppose it depends on what you mean by works.. can we cause precipitation (yes - [0]) or change precipitation (yes - [1] regularly done to decrease hail magnitude). [0]: https://www.cbc.ca/radio/quirks/feb-29-coronavirus-containment-window-closing-whale-skin-care-gingko-trees-eternal-youth-and-more-1.5479343/we-ve-been-cloud-seeding-for-decades-but-now-we-finally-know-it-works-1.5479347 https://www.cbc.ca/radio/quirks/feb-29-coronavirus-containme... [1]: https://letstalkscience.ca/educational-resources/stem-in-context/what-cloud-seeding https://letstalkscience.ca/educational-resources/stem-in-con...
- rdiddly 3y ago
  [flagged]
jjk166 3y ago
Cloud seeding alters precipitation patterns by single digit percentages. While this might be economically important, it would probably not be an effective method of hydrological warfare. Only a very select set of places could be targeted, it would take a very long time to have any practical effect, and it would be obvious long beforehand what was happening and who was doing it. Seems like a really easy way to give your neighbor a casus belli against you while in no way restricting their ability to wage war.
sacnoradhq 3y ago
If it were feasible, China would be sabotaging the US and India. Unfortunately, it would be both obvious and very, very expensive.

earthscienceman 3y ago

I'm an atmospheric scientist who has written/contributed to papers on cloud microphysics, albeit in the Arctic. I have not directly researched cloud seeding but do have the background to understand the dynamics at play. The answer is, at agricultural scales, absolutely not. What I think is interesting though is that your comment on "hydrological warfare/competition" is extremely relevant. Geo-engineering is almost always a hack with "no free lunch" impacts. For cloud seeding specifically, there is only ever so much water vapor available in the atmosphere and the efficacy of seeding depends on the dynamics/microphysics at play in the region of interest. If there is a lack of the specific aerosols necessary for condensation and precipitation, cloud seeding has shown to be effective to the tune of 5-15% increase in precip in certain regions. Water vapor doesn't like to hang out available in the atmosphere in large quantities so squeezing it out by forcing precipitation via "seeding" isn't really a reasonable concept. But to the degree that you do succeed, you are extracting water vapor that would have been transported by the atmosphere to other neighboring regions. While there is little evidence that cloud seeding can be done at-scale, in a world where someone comes up with a novel+clever idea this would mean that the impacts on precipitation in other regions would be significant. Again, no free lunch. It's not a stretch to imagine turning that into a competitive advantage or using it as a warfare tactic. If there were large bands of moisture just waiting to fall out of the sky we would be living in a very different climate. Aerosols are far too common on earth. In fact, the Arctic is one of the only places seeding makes a lot of sense with supercooled water and a distinct lack of aerosols in the clean environment. But in my research I have yet to come across much agriculture up there much less agrarian societies ;)

crznp 3y ago
If we imagine that excess water from Wyoming is used to grow crops in California, it seems reasonable to assume that it would be less moisture/precipitation for Nebraska. But if it is used to grow wheat in Colorado (because the obligations to lower-basin states need to be met regardless and the increased moisture allows more diversions across the continental divide), then it probably ends up evaporating anyway or else in the Platte River. It wouldn't be stealing moisture from Nebraska, they might actually benefit from it. Geo-engineering might not have a free lunch, but it also isn't a zero-sum game.

galuvian 3y ago

Maybe and yes. It violates the Geneva Convention. But I’m sure there would be ways to ‘justify it’ if a country wanted to do so. I had expected that it was not economically viable for agriculture, but the article has one source claiming it is actually quite affordable, given current water prices in the west. A large portion of the article tries to give both sides a voice. https://en.m.wikipedia.org/wiki/Weather_warfare https://en.m.wikipedia.org/wiki/Weather_warfare

gnabgib 3y ago

Yep, in 2017[0]. Suppose it depends on what you mean by works.. can we cause precipitation (yes - [0]) or change precipitation (yes - [1] regularly done to decrease hail magnitude). [0]: https://www.cbc.ca/radio/quirks/feb-29-coronavirus-containment-window-closing-whale-skin-care-gingko-trees-eternal-youth-and-more-1.5479343/we-ve-been-cloud-seeding-for-decades-but-now-we-finally-know-it-works-1.5479347 https://www.cbc.ca/radio/quirks/feb-29-coronavirus-containme... [1]: https://letstalkscience.ca/educational-resources/stem-in-context/what-cloud-seeding https://letstalkscience.ca/educational-resources/stem-in-con...

rdiddly 3y ago
[flagged]

jjk166 3y ago

Cloud seeding alters precipitation patterns by single digit percentages. While this might be economically important, it would probably not be an effective method of hydrological warfare. Only a very select set of places could be targeted, it would take a very long time to have any practical effect, and it would be obvious long beforehand what was happening and who was doing it. Seems like a really easy way to give your neighbor a casus belli against you while in no way restricting their ability to wage war.

sacnoradhq 3y ago

If it were feasible, China would be sabotaging the US and India. Unfortunately, it would be both obvious and very, very expensive.