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Comment by karaterobot | Hacker News Reader

With marine cloud brightening, which is what this article is about, they spray seawater into the air. They spray it over the ocean. It falls back down pretty quickly, since it's just water, and it doesn't genetically modify anything, because it's just water.

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We don’t know what the second and third order effects would be. We can’t even correctly predict what the weather will be 3 days in advance. No chance that we can predict what the consequences of such a significant and never been done change would be.

Seems like a high risk play, only to use as a last resort to me.

I agree, though it seems reasonable to trial it at a small scale as soon as possible so we can gradually scale it up and understand these second and third order effects with minimal risk.

Agree, it’s the only way for us to test our assumptions.

I wonder how well the experimentation approach will work in this case though, as:

1. Effects might be subtle and outside of the expected impact area.

2. Timescale might be really important (effects over a time much longer than we anticipate. Or even a timescale that makes it impossible to run many experiments in reasonable time)

I think this is a general argument that you can make about any risky enterprise (e.g., GMOs, vaccines, etc). There's always the possibility that your testing is inadequate, you can never drive risk to 0, etc. But by starting small and scaling up very gradually (while studying carefully the whole time) you maximize the risk that you will find and mitigate problems early and "cheaply" (i.e., without committing to applying the technique to the entire world).

Anyway, the idea is to have an ace in the hole in case we run out of other options to reduce climate change--at that point, the question is "which is less risky, geo-engineering or runaway climate change?".

As these things go, it's the lowest risk play I'm aware of. You can use it in a fairly specific area, like for example over a melting ice sheet. If you stop actively using it, the droplets precipitate out after a week or two, and everything goes back to the way it was. The biggest drawback, in fact, is that it is not permanent.

Dropping salt on a melting ice sheet does not sound like a great plan.

We'd really need to invest in really detailed computer models to make sure we're not overlooking something and shooting ourselves in the foot, IMO.

Well, if civilization was destroyed by spraying a fine mist of sea water into the air from the back of a boat, I guess I would feel pretty bad. But, that seems highly unlikely, and certainly less likely than that we'll destroy ourselves by continuing to do absolutely nothing to stop the climate from collapsing.

I imagine there would be an extremely large energy cost to spraying such boatloads of water in the air.

Wind and solar power both work well in oceans. You could spray water near wind farms during off peak hours, for example.

Solar might not work well if you're generating clouds.

>You could spray water near wind farms during off peak hours

I think underestimate the carbon cost of this infrastructure and the amount of energy needed to send this water into the air. Chances are it's not going to be doing a whole lot and pales in comparison to the amount of water evaporating and going up due to global warming.

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