To Geoengineer or Not to Geoengineer

by Bill Chameides | June 24th, 2009
posted by Erica Rowell (Editor)

Permalink | 1 comment

This is a satellite image of a phytoplankton bloom in the Southern Ocean. One questionable geoengineering technique would add iron to oceans to swell the numbers of phytoplankton, thus increasing how much CO2 they draw from the atmosphere. (NASA)

Imagine tinkering with the climate system to cancel out global warming — the stuff of mad scientists or global saviors?

As part of the National Academies’ study on America’s Climate Choices, we held a workshop in the nation’s capital last week on geoengineering. If nothing else, it was fascinating. So let me wax scientific and poetic on it.

How can we deal with global warming? Let me count the ways, starting with the most obvious:

  1. We must mitigate or limit global warming by decreasing greenhouse gas emissions.
  2. But doing this will be difficult: our energy infrastructure is carbon-intensive, and even if we stop all emissions today, some warming will continue for another 20-30 years. And so in addition to mitigating, we must also adapt, cope with the changes global warming will bring.
  3. But what happens if we can’t slow greenhouse gas emissions fast enough? Or that climate disruptions occur faster and more intensely than we predicted — so much so as to overwhelm any adaptation measures we take? Then what? That’s where geoengineering comes in. Maybe.

Geoengineering attempts to proactively change the climate system to counteract the effects of the warming caused by the emissions of greenhouse gases that come from burning fossil fuels and cutting down forests.

Two Broad Categories of Geoengineering

The Benign Procedures: Certain relatively benign measures seek to remove carbon dioxide (CO2) from the atmosphere artificially. The process involves exposing air to a chemical surface that reacts and removes the atmospheric CO2 (see here for example). This is a great idea; I say full steam ahead.

Unfortunately there are some kinks that have to be worked out:

(i) making the reaction efficient enough and the reaction surface large enough to remove CO2 on a global scale without expending inordinate amounts of energy, and

(ii) safely storing the captured carbon (which is the same issue that carbon capture and storage, or CCS, must address).

The second issue is close to being in hand, the first less so.

The Invasive Procedures: More radical approaches seek to change the way the Earth’s climate system works. Here are some for instances.

  • The ocean fertilization approachinvolves adding iron to the ocean so that phytoplankton, important microscopic organisms at the bottom of the marine food chain that take up CO2 during photosynthesis, bloom and draw CO2 from the atmosphere.On paper this seemed to be quite promising. In practice, not so much. Phytoplankton do not appear to draw as much CO2 out of the atmosphere as had been thought (see here and here) And, more importantly, ocean fertilization could profoundly, and potentially deleteriously, change ocean biology. At the geoengineering workshop last week, most agreed this is a non-starter.
  • Increasing the Earth’s reflectivitymeans the Earth absorbs less sunlight and therefore less heat, thereby counteracting greenhouse gas warming. This invasive procedure received a lot of attention at the workshop.There are a number of ways to enhance the Earth’s reflectivity: for example, by placing large mirrors in the Earth’s orbit or injecting reflective particles into the stratosphere. Actually we would likely inject a sulfur containing gas that would be converted into sulfate particles. (Painting roofs white would also help but is unlikely to provide a global scale cooling cure.)

    Calculations suggest these reflective measures could work, but lots of problems would have to be worked out first. Some are just plain engineering challenges, like how do you inject tons of stuff into the stratosphere on a continuous basis? Or how would you place huge mirrors in orbit?

    Other problems are more fundamental and worrisome, like how do we know that monkeying with the Earth’s reflectively won’t cause more serious problems than what this climate-cooling measure seeks to cure? For example, it could in theory shut down the Indian monsoon.

    Another problem: the reflective approaches do nothing to stop the build-up of carbon dioxide and thus will not avert ocean acidification. It would even make other parts of the climate cure, like solar thermal energy, less effective.

The Addiction Trap

The reflective measures pose another interesting problem that I call the “addiction trap.”

Imagine we start injecting particles into the stratosphere to counteract the Earth’s warming but we do nothing to reduce CO2 emissions.

As emissions continue to grow, we would need to increase the amount of stuff we inject to provide more cooling and keep temperatures copasetic.

Now, say it’s 50 years later and, for some reason, we discover that we need to stop the injections, or maybe terrorists interrupt the delivery of particles to the stratosphere. We are in big trouble.

If the injections stop, the particles we injected will fall out of the stratosphere in a couple of years, and once they do, we will feel the full force of the greenhouse gas warming with all that additional CO2 now in the atmosphere. In other words, once we use the reflectivity cure, we will be in danger of having to rely on it indefinitely — needing ever greater amounts of reflectivity to counteract ever greater amounts of CO2. Sure sounds like an addiction to me.

More Study Needed

The invasive geoengineering procedures may offer potential, silver-bullet cures for global warming, but they may actually prove to be poison pills. Virtually all of the scientists at last week’s workshop acknowledged this, but still maintained that we should continue to study geoengineering techniques from the perspective of:

  • how they might be implemented and
  • how they might affect the climate and environment.

Why? Because many believe that we may need to try one of them some day — either as an emergency measure to avert an impending calamity or as a stop-gap measure to buy us more time to rein in CO2 emissions. I tend to think research can’t hurt and we may learn some new things in the process.

The Role of Social and Political Scientists in the Debate

But while the scientists explore the physics of geoengineering, social scientists better be thinking about a host of other issues:

    1. Ethics: Many hold that geoengineering is unethical because we’d be interfering with the natural world without knowing what might happen. (And given the complexities of the climate system, I think it’s unlikely that we would ever fully know the consequences of invasive geoengineering.)

But there is another side to the coin. Suppose 500 million or a billion people were threatened by a climate calamity (like the loss of water on the Indian subcontinent) and injecting particles into the stratosphere might save them. Or suppose a major, irreplaceable ecosystem like the Amazon rain forest were at risk. Is choosing not to act to save them ethical just because of a fear of unknown unintended consequences? How, as a global community, do we weigh these competing arguments?

  • International Issues: Geoengineering has geopolitical implications. Unde
    r what circumstances, how, and who would decide to undertake a geoengineering project. Can an individual country decide to geoengineer on its own? Suppose a country implemented a geoengineering project that benefited its people but had negative consequences for another nation? What steps could be taken to rectify the harm short of a declaration of war? Should there be an international body in charge of geoengineering? And if so, how would it be established and how would it enforce its rulings?


And to think this all started when someone had the bright idea to burn a little fossil fuel. Now there’s an addiction for you.

filed under: carbon dioxide emissions, climate change, faculty, fossil fuels, global warming, oceans, science
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1 Comment

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  1. Lucas
    Jul 6, 2009

    As you said, we must sequester CO2 now to halt and reverse ocean acidification. IMO, the only safe approaches to geo-engineering are cool roofs (green roofs, white roofs), lightening other paved surfaces and biochar. If biochar works, it is the closest thing to a silver bullet in the geo-engineering toolbox. Biochar has so many benefits that it can’t be too good to be true.

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