« Topsight, March 15, 2009 | Main | Geoengineering: New Problems, Old Politics »

Geoengineering's Drawbacks

Because I'm not reflexively opposed to geoengineering research, and because I increasingly suspect that some level of albedo-management geoengineering will be necessary simply due to climate disruption happening faster than previously expected, some people tend to assume that I'm a geoengineering advocate. I'm not -- but as I've noted before, I do believe that it would be less disastrous than climate-driven depopulation. Nonetheless, geoengineering is all-but-certain to have undesirable consequences, both politically (see next post) and environmentally.

This week we got an excellent example of the latter.

Using well-established data on the light-diffusing effects of aerosol particles, Daniel Murphy [at the National Oceanic and Atmospheric Administration's (NOAA's) Earth System Research Lab] calculated that the geoengineering scheme currently envisioned could reduce incoming sunlight by about 3%. That squares with data from the Mount Pinatubo eruption.

The geoengineering scheme would also mean 3% less sunlight reaching flat photovoltaic collectors that generate electricity. But the aerosols would cut the available solar radiation even more to dish- and tube-shaped collectors that use mirrors to concentrate sunlight. Murphy's research shows that for every watt per square meter of sunlight diffused by the aerosols, as much as 5 watts per square meter would be made unavailable to mirrored collectors on the ground.

This is a problem, but not a fatal one. Commercially-available photovoltaic cells remain painfully inefficient, so one of the best ways to increase the energy returned from a solar array is to use concentration. High-atmosphere particles tend to scatter light, however, and diffuse light doesn't concentrate as well as direct sunlight.

There are a few caveats:

  • Solar isn't the only renewable option, and concentrated solar -- while the best energy-producer per square meter -- isn't likely to be the dominant form, at least once cheap solar plastics become more widely available.
  • Concentrated solar doesn't become useless, just less-efficient.
  • Most importantly, the leading proposal for stratospheric sulphate injection geoengineering would have it happen primarily at the poles; warming at the poles has a much greater feedback effect than equatorial warming, and is much more critical to prevent.

    Solar, concentrated or otherwise, isn't likely to be a critical energy source at the poles, so the reduction in solar efficiency resulting from stratospheric sulphate geo would be less important if the geo focuses on polar regions.

    Even if this turns out to be a minor drawback, it's an important indicator that no one response to global warming is perfect. Even carbon emission reduction has negative repercussions -- up-front expense in some cases, time required in others, and even the possibility of a short-term increase in warming due to the removal of atmospheric particulates (shutting down coal plants means more than reducing CO2, it also reduces soot and other pollutants -- yay for our lungs, but clearer skies mean warmer Earth). Still, geoengineering, because of its scale and the complexity of its subject, is highly likely to offer up more of these dilemmas.

  • Comments

    Methane management may be much more important than carbon management in the short term. I'd concentrate my energies there first.

    Wow, we are amazingly myopic as a species, if that's one of the more prominent examples of "undesirable consequences."

    I think people might assume that you're a geoengineering advocate because that is the natural tendency of your argument. If not an advocate, you're just a few short assumptions and scale of spatial/temporal thinking away from becoming one.

    Josh, it's not the harshest of the undesirable consequences, but it is the most recently-noted -- and one that operates in direct opposition to parallel goals.

    As for whether or not I'm an advocate of geoengineering, my take on advocacy is that it asks/demands whatever is being advocated as a preferred action. I'd much, much rather that geoengineering not be necessary -- it's by no means my preferred action. I do, however, recognize that it may become necessary, and so what I advocate is what I note in my subsequent post: research, transparency, and cooperation.

    Jamais isn't advocating, he is cautioning. One doesn't caution about improbable acts, just those with significant likelihood. Jamais has been at the forefront of those recognizing the increasing probability of geo-engineering. This post is a clear illustration of the need for caution: policies are being proposed by people who aren't thinking through the consequences.

    Reverence, or whatever is the opposite of hubris, reminds us that playing God will never make us God. If we must geo-engineer, we'll need to do so with foresight, humility and transparency. I believe that beholds us to work first on those techniques that have the least likelihood of harm and as many other, synergistic benefits as possible.

    By that test, there's seems much more merit in increasing soil organic matter, by biochar and other means, in planting agricultural forests, in new ways of growing rice, in a reduction of meat consumption, than in iron-fed algae blooms or stratospheric aerosols. Whether these more-benign efforts will be enough, I don't know - but I believe that is where we should start.

    Cutting down sunshine has many more problems than solar collectors!
    The main one: carbon dioxide continues to acidify the ocean, even though we try to preserve the polar ice. We lose plankton at the bottom of the food chain, not to mention coral.
    Closing coal plants may allow us to feel more of the warming we have caused, but it stops the progress of the climate toward Venus-like conditions....
    Radio Ecoshock

    Nobody with any sense would (or should) claim that any geo-engineering project will 'solve the problem' (which is, as Alex Smith points out, an excess of CO2). At best, it will give us a bit more time to solve the problem.

    One aspect of the aerosol approach hasn't been mentioned: that it is part of a bit of inadvertent geo-engineering already. Contrails contribute about 1% to the warming effect. Why not put sulphates in them to neutralise or even reverse this?

    Post a comment

    All comments go through moderation, so if it doesn't show up immediately, I'm not available to click the "okiedoke" button. Comments telling me that global warming isn't real, that evolution isn't real, that I really need to follow [insert religion here], that the world is flat, or similar bits of inanity are more likely to be deleted than approved. Yes, it's unfair. Deal. It's my blog, I make the rules, and I really don't have time to hand-hold people unwilling to face reality.


    Creative Commons License
    This weblog is licensed under a Creative Commons License.
    Powered By MovableType 4.37