Section 3: Geoengineering

    Some further resources:
  • A broad introduction to geoengineering
  • A few years ago Scientific American had a nice article covering certain approaches and their risks.
  • The National Academies report on the subject is worth reading, as is a European equivalent.
  • A group at Leeds in the UK has a great site on integrated (technological, social, economic) assessment of geo-engineering proposals.
  • I would also recommend checking out the slides from this graduate course on the subject.
  • A recent technical evaluation of geo-engineering approaches was recently published by Lawrence et al, which I cite heavily below.
  • A first principles calculation paper from 1992 is also worth looking at.
  • An article by Deutch and Zuber, with Zuber being one of the chairs of the President’s advisory council on science and technology
  • Ezra Klein featuring Elizabeth Kolbert’s new book called Under a White Sky: The Nature of the Future
This is the third of a series of three blog posts intended as a primer on how technology can help to address climate change. This post — meant more as a reference collection and literature review than any kind of position statement — is a summary of what I learned at a technical level about the controversial topic of potential engineering interventions, i.e., “geo-engineering”. These include solar radiation management, and direct interventions to slow the loss of sea ice.


Given the more controversial nature of geoengineering I thought I'd add a few caveats/disclaimers specific to this section.

  1. Geo-engineering should not be seen as an alternative to rapid deployment of renewable energy and other decarbonization technologies. In the case of solar radiation management at least, doing so, as pointed out by many key quotes in this excellent Scientific American article, could be dangerous. Specifically, imagine a very-high-carbon scenario coupled with a solar shading mechanism that was suddenly turned off for some reason; that could create a much more unstable situation with rapid warming. Even if such a shading mechanism worked well and was not turned off, it would be highly problematic if it was used as a “bandaid” while action to decarbonize the economy and prevent other effects like ocean acidification was delayed.
  2. To reiterate, it is very important to limit CO2 and other greenhouse gas concentrations in the atmosphere, and possibly ultimately bring them back close to pre-industrial levels through sequestration, for a variety of environmental reasons other than the impact on the average global temperature (“global warming”), e.g., ocean acidification and potentially changes in rainfall distribution. A paper by Ken Caldeira’s group notes, for example, that a significant fraction of existing coral is already in trouble due directly to ocean acidification (some are trying to help). Also, don’t forget that particulate air pollution from, e.g., coal power plants, is also a big health problem, not addressed by solar geo-engineering.
  3. No single conceived solar geo-engineering technology would effectively stabilize all forms of dangerous climate instability, e.g., solar radiation management may not be able to stabilize undersea melting dynamics of the Antarctic ice
  4. It would probably not be easy to build a consensus around the use of such technologies, at least in the present geo-political environment. They are not without real risks. There are also concerns that they would impact different regions differently, exacerbating potential ethical and political issues. (In general, these technologies would not perfectly restore a lower-CO2 climate: they would lower average temperature, but each individual locale would not necessarily return to the exact temperature or precipitation features that it had at lower CO2.)
  5. These technologies are still basically just ideas. It would take years or decades to work them out just at the engineering level to the point where they could be reliably and practically applied.
  6. This post does not cover the policy and human dimensions, which are clearly in many ways more challenging than the technical dimensions, and are extremely important. As a result, this post is admittedly woefully incomplete. In particular, even if the technology was basically perfect, the moral hazard issue is a real one. Should we be developing solar radiation management faster, because of the potential for emergencies, its likely cost effectiveness and speed for certain purposes (but not others), and the fact that any technology takes time to prove out and refine? Or should we be developing it slower because vested fossil fuel interests would use any progress on these lines as ammunition in a massive ongoing lobbying campaign to slow their inevitable decline while maximizing their profits.

    These are separate questions from whether the technology is going to be effective, safe, equitable, controllable, localized, and so on. I don’t have an answer for it, but I will point out the following. The lack of a viable solar radiation management approach should ideally not need to be a necessary weapon against excuses from fossil fuel emitters to keep emitting — we should have a whole arsenal deployed, like carbon taxes, fines, and crucially lower cost carbon-free alternatives. Would we need to postpone development of solar radiation management technologies if we had a strong carbon tax or cap in place already? What if renewables + storage + a bit of small modular nuclear was at 1/10 the price of coal for grid-scale electricity (and we had cost effective carbon-free versions of steel and cement manufacturing and so forth)?

    Alas, we don’t have a trillion dollar entrenched industrial base trying to start fires… in that case, we’d sadly have to ask about the net benefit of bringing about the potential arrival of fire extinguishers sooner versus later.)Whether we in practice need to hold back this R&D for moral hazard reasons, at the moment, is a real question, but we should be able to shut down fossil fuels regardless — without needing to hold back research on emergency adaptation approaches — just as we have strong laws against arson, and fire-safe buildings, but still keep fire extinguishers around just in case.
  7. My purpose here is simply to review what the existing technical literature says about what physics and technology might allow. It is intended as a set of pointers to already-published technical material. I’m not prescribing any particular action or inaction beyond what has been published.

One framing of geoengineering is that we are playing God and intervening in ways we can’t possibly hope to understand. There are definitely worries around trying to influence global weather and climate in these kinds of ways and that is largely why we aren’t doing it at the moment. However, an alternative viewpoint put forward by Kelly Wanser is to liken the current biosphere not as pure nature but as something we have already polluted. In other settings, like oil spills, when we devastate nature even if our fixes are radical they can be justified if the damage we have done, are doing, is great enough and some would say that may well be the case with the climate as a whole today.

With that said, I’m not sure I can do better in advocacy of analyzing these potential technologies than by a) linking to a US presidential candidate already discussing them (and not incoherently either) and b) emphasizing that we still don’t perfectly understand potential tipping points in climate dynamics (or for that matter global human social dynamics) that could lead to emergency scenarios where a diverse portfolio of technological options might be needed.