No silver bullet: why geoengineering alone won’t save the planet – Guest Post – David Morrow, Institute for Philosophy & Public Policy at George Mason University


Erin Biba’s Newsweek article on geoengineering commits one of the classic blunders in thinking about geoengineering: treating it as if it might be a silver bullet capable of “solving” climate change. Biba writes that geoengineering “can either bypass governmental red tape or reverse [climate] change so quickly and with such great efficacy that it might not matter if the world never manages to get its act together.” This is an easy mistake to make, but an incredibly important one to correct. Geoengineering may someday have a role to play in climate policy, but it will never be more than a supporting role. The stars of the show will have to be emissions reductions and adaptation. Here’s why.

Geoengineering comes in two flavors, which I’ll describe below. Each kind has its distinct advantages and disadvantages. One is expensive, slow, but comprehensive. The other is cheap, fast, and imperfect.” Even a combination of these approaches would be too expensive and imperfect to constitute an affordable, effective response to climate change. Such a response simply isn’t possible without slashing greenhouse gas emissions.

The slow, expensive option is to suck carbon out of the atmosphere and lock it away. (Scientists call this “carbon dioxide removal.”) Biba gives three examples of this approach—ants making limestone, Andean farmers reforesting their land, and ships fertilizing the oceans with iron. Other proposals include biomass energy with carbon capture and sequestration, scattering a mineral called olivine, burying biochar in fields, and capturing greenhouse gases directly from the air using giant carbon-sucking machines If these proposals can be made to work without excessive side effects, they could be a useful addition to the climate policy toolkit. And only these kinds of proposals can turn back the clock on climate change by pulling greenhouse gas concentrations back down to safer levels. But all of these proposals share two features: They are slow, and they are expensive. Because they’re slow, they would require an enormous effort over many decades just to undo what we’ve already done. To try to use them to compensate for unmitigated future emissions would be even harder, requiring a larger and longer effort. And because they’re expensive, they would require an enormous and growing investment over those decades of deployment. It would be much cheaper just to reduce our emissions in the first place. Furthermore, it’s unlikely that anyone would pay for them without “governmental red tape” creating a program to pay people for sequestering carbon.

The other kind of geoengineering tries to reflect sunlight back into space before it has a chance to heat the Earth, much as putting up an umbrella at the beach keeps you cool by blocking the sun. (Scientists call this kind of geoengineering “solar radiation management” or solar geoengineering.”) Biba mentions one proposal of this kind—injecting sulfates into the stratosphere to mimic a volcanic eruption. The other prominent proposal is to use sea salt to brighten clouds over the ocean. As Biba notes, these methods would cool the Earth quickly and—we think—cheaply. So they don’t suffer from the same problems as the first kind of geoengineering. And because they can slow or even halt rising temperatures, they could probably prevent or reduce some of the damages that climate change will cause. But considered as complete solutions to climate change, they too have their problems: First, they do nothing to address ocean acidification, which Elizabeth Kolbert calls “global warming’s equally evil twin.” To stop ocean acidification, we need to stabilize or even lower greenhouse gas concentrations in the atmosphere, which is only feasible with major emissions reductions. Second, these kinds of solar geoengineering have side effects, and the side effects grow worse as we rely more and more heavily on them. When combined with serious emissions reductions, modest levels of solar geoengineering might be attractive. In that kind of scenario, the side effects might be tolerable—although we don’t yet know enough to be sure about that. But we can be confident that if we keep pumping greenhouse gases into the atmosphere, trying to keep temperatures constant will eventually create intolerable side effects. The worst side effects of solar geoengineering, like some of the worst effects of climate change itself, have to do with rainfall. As we try harder and harder to ward off more and more warming, weather patterns around the world will begin to change. In many places where poor farmers depend on rain to survive, such as India and the African Sahel, seasonal rains may fail. In short, if we rely exclusively on solar geoengineering, we won’t stop climate change; we’ll just change climate change.

To impose those costs on the most vulnerable because “the world cannot get its act together” would be a gross injustice.

This last point raises a crucial issue that Biba doesn’t address at all: the issue of fairness. Geoengineering, and especially solar geoengineering, comes with serious side effects. The worst of those costs are likely to fall most heavily on the people least able to bear them—the poorest of the global poor, whose lives could be ruined or even cut short. To impose those costs on the most vulnerable because “the world cannot get its act together” would be a gross injustice.

Like Ken Caldeira, whom Biba discusses in her article, I’m “negative about all the geoengineering options.” But also like Caldeira, I recognize that some of those options could help reduce the very serious dangers of climate change. And so, I believe that geoengineering might someday be part of a sensible package of climate policies, as long as that package includes major emissions reductions. But in thinking about those policies, we must always remember one thing: geoengineering is not now and never will be an alternative to dramatic reductions in our greenhouse gas emissions. It is no silver bullet.


david-morrow_large-photo-2David Morrow is currently a Visiting Fellow at the Institute for Philosophy & Public Policy at George Mason University. He taught in the Philosophy & Political Economy program at the University of Alabama at Birmingham from 2010 to 2014. He has published on the ethics and governance climate engineering in venues such as Climatic Change, Environmental Research Letters, Philosophical Transactions of the Royal Society, and Ethics, Policy & Environment.

  • nicholbrummer

    The last IPCC report specifically mentions that we probably won’t be able to stay under 2ºC without a good measure of Carbon Dioxide Removal. The Olivine method seems like it may have a reasonable cost, and it has potential to scale up. It also is one of the few methods that directly removes acidity from the seas.

    Here’s a link to a pretty detailed description by one of the proponents, Olaf Schuiling:

    For quick diagonal reading: sections 1,2,3 (intro), then 11 (cost), 15 (examples of side benefits), and if you’re interested in the geochemical details of how it really works read 7,8,9,10. If you’re still curious, read the remainder 🙂