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The price of uncertainty: geoengineering climate change through stratospheric sulfate

With thanks to Clive Hamilton for his talk.

Stratospheric sulfate seems to be one of the most promising geoengineering methods to combat climate change. It involves the injection of  hydrogen sulfide (H2S), sulfur dioxide (SO2) or other sulfates, into the stratosphere. Similar to what happens after major volcanic eruptions, this would reflect off part of the sun’s energy and cool the Earth, counterbalancing the effect of greenhouse gases (see for instance the “Year without a Summer” that followed the 1815 eruption of Mount Tambora).

It is probably the best geoengineering solution to climate change, in that it’s likely to work, should be technically feasible, can be done by a single nation if need be (no need for global consensus), and is likely to be very cheap – especially in comparison with cutting emissions. But it has a few drawbacks:

  1. It will have unpredictable effects on the weather across the globe.
  2. We can’t really test it – the test would be doing it, on a global scale.
  3. We wouldn’t know if it worked until we’d had about a decade of temperature measurements.
  4. Once started, it’s extremely dangerous to stop it – especially if carbon emissions keep rising.

So, should we do it? Narrow cost-benefit analysis suggests yes, but that doesn’t take into account the uncertainty, the unknown unknowns – the very likely probability that things will not go as expected, and that we’ll have difficulty dealing with the side effects. This includes the political side effects when some areas of the globe suffer more than others from this process.

How bad does global warming have to get before we consider this type of nearly irreversible geoengineering? If we had to choose between this and cutting emissions, how high would the cost of cutting have to go before we sprang for this instead? In short, what price do we put on avoiding uncertainty on the global scale? Can we estimate a dollar amount, or some alternative measure of the cost – quality-adjusted life years, or some other human-scale estimate? Or is this an illusionary precision, and do our intuitions and qualitative arguments (precautionary principle?) give us a better estimate of whether we should go ahead with this?

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6 Comment on this post

  1. I’m hesitant to even call this a solution, since it doesn’t solve anything. It simply is dealing with a symptom of the problem. Rising temperatures is an effect of the CO2 that we’re putting into the atmosphere. So when the effects of the temporary solution go away, all the while, we’re still pumping CO2 into the atmosphere, we’ll end up needing to utilizing the geoengineering “solution” more often, since the planet will heat up all the more quickly. We literally become addicts with this solution. Not to mention the harms that come with reduced sunlight…. reduced photosynthesis, reduced crop yields (which were some of the effects of the year without a summer). I don’t see how anyone can seriously think of this as a solution still…

  2. There is considerable evidence that programs similar to what is described here are already underway globally. Heavy spraying out of airplanes is common across much of North America and spending a few hours on YouTube confirms the same globally. Unfortunately, the chemicals showing up in rainwater and snow samples across North America have been found to contain unusually high levels of Aluminium, Barium, and Strontium, not the sulfate compounds addressed in this article.

    If you have a hard time believing that these programs are already being implemented, perhaps you should spend more time studying the sky and less time in front of the computer. Peace!

  3. Of course it would be nice if governments started making more aggressive regulation and taking existing regulation more seriously, but I guess that’s not very likely so we end up doing weirder things instead. I rather liked the idea someone had of rolling aluminum foil out over deserts in order to adjust albedo. I saw speculation that it would cost several billion dollars to do it well, but weighed against global catastrophe that didn’t seem so bad. It seems to me that if you did this in pieces, you could at least adjust it by folding up some of it to make adjustments if it wasn’t working. I think undoability or adjustability should be taken into account on solutions, though it’s true that the situation can get bad enough that even such “niceties” may not be practical. Are we there now? I wish I thought government were even trying to assess that. World government plans for action seem to be going on way too slow a timeline, as if they’re all in total denial.

    I also think we can’t afford to rule out solutions like modern nuclear. Even though modern nuclear technology is safer than many of the old systems we’ve seen problems with, there are risks with nuclear. Still, the risks of Climate Change seem higher at this point and we need a solution we can readily deploy without waiting for research and without waiting for industry to deploy alternate delivery mechanisms. Failing to use nuclear doesn’t mean zero risk, but rather more fossil fuels, which is already known to be a huge risk. One cannot rely on the status quo to be safe.

  4. It appears to us likely that geoengineering measures will be deployed. At the present, short term economic constraints guide pretty much all so called development.

    People want as much luxury as they can afford, corporations are happy to provide and profit, and Governments enjoy the tax revenues.

    Unless this cycle is interrupted, geoengineering measures will likely be deployed.

    What to do? If you care as much as you write, go for a walk, ride a bike, eBike, take transit or try an EV. Do something personally.


  5. I think a lot of climate folks would disagree with your assertions that “Stratospheric sulfate seems to be one of the most promising geoengineering methods to combat climate change” and that “It is probably the best geoengineering solution to climate change”. See the Royal Society report – it’s true that of the solar radiation management (SRM) techniques it gets a fair amount of play, but I’d guess that most scientists prefer carbon dioxide removal (CDR) approaches, even though these are more expensive under today’s technology. I apprecitate that the aim of your post was “suppose SRM is the way to go…” but I think you might have rather oversold the geo-engineering case. In the interests of adding some scientific context, here’s the IPCC’s report on the Lima Geo-Engineering meeting:

    Personally, I’d be very sad if the world did something really dumb (SRM) because it was scared there was a small probability of catastrophe, when more moderate approaches to would argue for traditional mitigation (defossilisation of electricity, electric vehicles, etc). It would be like getting bitten by an insect and amputating your leg because someone (Clive, say) persuaded you that there’s a small but non-negligible chance that your bit will get infected, leading to full-blown sepsis. Better to be safe with one leg than dead with two, eh? I think this is a classic case of “be careful what you wish for” – attempts to stimulate action by emphasising the scary but fringe possibilities around climate change might not stimulate the actions you were hoping for…

    1. Thanks for the info! I’ll look into that.

      >attempts to stimulate action by emphasising the scary but fringe possibilities around climate change might not stimulate the actions you were hoping for…

      I doubt I have much possibility of stimulating action in any way on this topic 🙂

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