Engineering Our Way Out of Global Warming: Is Climate Intervention a Global Warming Solution That Republicans Will Get Behind?

Posted by on Mar 3, 2015

Schematic showing how albedo modification could reduce the amount of sunlight reaching the Earth's surface. Source: National Academy of Sciences

Schematic showing how albedo modification could reduce the amount of sunlight reaching the Earth’s surface. Source: National Academy of Sciences

As climate change has become ever more certain in recent years, the conversation is increasingly shifting from whether climate change is occurring and how to prevent it to what we might do about it. This is where adaptation comes into play: Plan B – creating more resilient systems that will allow us to function in an climate of warmer temperatures, more intense storms, rising sea levels, prolonged droughts, wildfire, and other sundry impacts.

Those of us advancing a discussion of adaptation—including the Resilient Design Institute—argue that we need to continue to do everything we can to prevent or slow climate change, but we also need to figure out how to live with the reality that the climate is changing with all of the above-mentioned ancillary impacts. To keep our families safe, to put food on the table, to ensure access to fresh water, to protect our coastal cities…there is a huge agenda that we need to face—and it’s likely that this agenda will become an overwhelming driver and focus of human society over the next century.

Or, is there another option? Some suggest that a Plan C could solve our massive climatic problems without all the dislocation and hardship, and without compromising our standard of living. A relatively small, but growing, voice is suggesting a technological fix to these problems: active climate intervention. This is the audacious idea of intentionally modifying the climate to compensate for the carbon emissions that we seem unwilling to curtail.

The National Academy of Sciences weighs in on climate intervention

The National Academy of Sciences (NAS) last month released two new reports that address the controversial idea of climate intervention, which some refer to as geoengineering. These reports, Climate Intervention: Reflecting Sunlight to Cool Earth and Climate Intervention: Carbon Dioxide Removal and Reliable Sequestration, will add tremendously to this highly important debate. While I believe that one of these reports missed a huge part of the opportunity that exists (more on that below), the reports demonstrate the tremendously important role that NAS should play in assessing complex issues and providing direction to the nation.

The NAS Climate Intervention reports a address two very different ways in which humans could manipulate the climate: first, by increasing the reflectivity of the earth, and second, by capturing and sequestering more of the carbon dioxide that we’re pumping into the atmosphere. The first of these options terrifies me; the second should be actively pursued.

Cooling the Earth by reflecting sunlight

Many of us studied the greenhouse effect in school. This is the process in which short-wavelength sunlight passes through a material (the glass of a greenhouse or the earth’s atmosphere) and is absorbed by surfaces that sunlight strikes (the planting beds in the greenhouse or the Earth’s surface). That surface warms up and, in turn, begins radiating long-wavelength heat radiation outward. But long-wavelength electromagnetic radiation doesn’t pass through the greenhouse’s glass; it is instead absorbed. Heat is trapped in the greenhouse. Some of the gases in the atmosphere, including carbon dioxide, water vapor, methane, and the alphabet soup of halogenated compounds like CFCs, HCFCs, and HFCs, act like the greenhouse glass and absorb that heat radiation emitted from the Earth’s surface, which as a result is warming.

To extend the greenhouse metaphor, the idea with the climate intervention strategy of reflecting sunlight (albedo modification in physicist lingo) is to put a special coating on the greenhouse described above: make the glass more reflective to the short-wavelength sunlight striking the glass. Less sunlight would then pass into the greenhouse, and it will cool off.

The NAS report, Climate Intervention: Reflecting Sunlight to Cool Earth, which can be downloaded in PDF form for free, does an excellent job at both describing the physics of this strategy and the risks. The strategies covered mostly relate to the seeding of the stratosphere with sulfur compounds to mimic what has occurred with major volcanic eruptions, such as Pinatubo in 1991 and Krakatoa in 1883, both of which ejected millions of tons of sulfur dioxide into the stratosphere and resulted in a global cooling effect.

Among the various risks articulated in the report are unintended consequences. Could such a strategy plunge us into an ice age? Could there be other, currently unknown effects of cloud seeding? And would reliance on such a strategy reduce our motivation to reverse greenhouse gas emissions?

The carbon cycle sequesters huge amounts of carbon dioxide; some of those natural processes can be enhanced by human actions. Source: National Academy of Sciences

The carbon cycle sequesters huge amounts of carbon dioxide; some of those natural processes can be enhanced by human actions. Source: National Academy of Sciences

Carbon dioxide removal and sequestration

The other climate intervention strategy is to sequester carbon so that less of it enters or remains in the atmosphere. On many levels, this is a far less controversial intervention strategy than reflecting sunlight, and the NAS reports make that abundantly clear (see chart below).

Carbon sequestration is what trees already do very effectively and, indeed, carbon sequestration by forests is a key part of metrics that look at the global carbon balance. Where intervention comes into play is in planting more trees, or managing forests to provide for greater, long-term sequestration of carbon dioxide.

Carbon sequestration in soils also offers a great deal of potential. Kristin Ohlson, the author of The Soil Will Save Us, which I recently read, suggests that by changing soil management practices almost all of our anthropogenic carbon could be captured and sequestered—and, furthermore, doing so would enable those soils to fare far better during droughts, erode less from heavy rain, and support far greater biodiversity. Though the carbon sequestration claims in the book are almost certainly exaggerated, the benefits of changing the way we manage agricultural land are huge and should become standard practice.

Better land management, which has an ancillary climate intervention benefit, is clearly a better option than conventional agricultural practice. There’s nothing not to like about it.

Carbon sequestration also can involve geologic processes. This happens all the time as marine organisms, such as phytoplankton, die and sink to the bottom of the ocean to form sediments and, over time, sedimentary rock. These sedimentary rocks are huge sinks of carbon, as we can see in the White Cliffs of Dover.

The NAS report, Climate Intervention: Carbon Dioxide Removal and Reliable Sequestration, describes how the chemical processes that produce some carbon-rich minerals can be replicated by humans through mineralization processes. The report does a poor job, however (in my estimation), in addressing some of the opportunities that exist for doing so through the manufacture of common materials. I have become quite excited about a number of technologies that exist to produce commodity materials, especially cement and concrete, in processes that sequester carbon.

Of these approaches, the one I’m most excited about right now is one being developed by Blue Planet, a company based in Los Gatos, California that was founded by Stanford professor Brent Constance. While the company is still operating in a stealth mode, I had an opportunity to spend a couple days with Brent at the BuildWell Symposium last year in California and found myself with a new level of optimism about the potential for carbon sequestration through cement and concrete production.

In a nutshell, Blue Planet technology would create a somewhat different type of concrete that sequesters carbon both in the cement and in the aggregate. The carbon source would be power plant or cement plant stack emissions, while calcium would be extracted from sea water or brine. The bulk of the sequestration would actually occur in the aggregate—by shifting from quarried (crushed) stone to synthetic limestone. Such plants could be co-located with desalination plants, as the processes are synergistic.

While the NAS report addresses mineralization as a carbon-capture and sequestration process, it fails to address the idea that this could be done through a commodity product, concrete, that is the most widely used construction material in the world.

Pros and cons of albedo modification and carbon capture. Source: National Academy of Sciences

Pros and cons of albedo modification and carbon capture. Source: National Academy of Sciences

We need to pay attention to climate intervention technologies

The NAS reports described here are the beginning of what should be a long—and exciting—discussion in scientific and political circles. While there is huge potential benefit with carbon capture, there are big risks with the enhanced reflectivity strategies that some are beginning to advance.

I am all for carbon-capture—both the research needed to better understand it and the implementation of strategies that employ it. But albedo modification (enhanced solar reflectivity) is a different story. I believe we should carry out fundamental research on this climate intervention strategy, but only consider implementing those ideas as a last-ditch strategy if the climate truly begins spinning out of control.

As the authors of the NAS reports explain, “Proposed albedo modification approaches introduce environmental, ethical, social, political, economic, and legal risks associated with intended and unintended consequences.” In short, it’s scary, and risky. Furthermore, albedo modification is something that would have to be maintained to achieve a continuous effect; if those efforts were to cease and there hadn’t been dramatic reductions in carbon emissions, global warming would pick up where it had left off before we started raising the earth’s albedo.

I agree wholeheartedly with the NAS committee that wrote these reports when they say it would be “irrational and irresponsible to implement sustained albedo modification without also pursuing emissions mitigation, carbon dioxide removal, or both.” I urge you to familiarize yourself with these issues.

My fear is that some in Congress who have to date denied the existence of global climate change will turn to climate intervention once they (finally) recognize that humans are indeed causing global warming. The dominion over nature argument may be compelling for climate change deniers once they no longer deny that humans are changing the climate. They will suggest that we can simply engineer our way out of the crisis, and by doing so we won’t have to alter our highly carbon-intensive ways.

Along with founding the Resilient Design Institute in 2012, Alex is founder of BuildingGreen, Inc. To keep up with his latest articles and musings, you can sign up for his Twitter feed. To receive e-mail notices of new blogs, sign up at the top of the page.


  1. Ocean Acidification is the unspoken threat.for 2 reasons … 1) it kills shell forming see life – the basis of the marine food chain. & 2) it kills plankton .. which produces half the oxygen which the seas release for humans (and other animals) to breath.

    CO2 will wipe us out even if we bounce back sunlight from putting crap in the atmosphere.

    We need to clean up our acts! … No CO2 Emissions – there are available and better ways than fossil fuel usage.

  2. Dear Alex:
    Thank you for this informative article.
    -Seeding of the stratosphere with sulfur compounds might very well lead to increased acidification and ocean phytoplankton kill;
    -The transportation industry is a significant contributor to
    CO2 and greenhouse gases from exhausts/tailpipe emissions. We
    need to switch to clean sustainable wind power and distributed
    solar asap. An article which I wrote in 2014 is linked here:
    -EPS (expanded polystyrene) foam for much modern building use is dependant on petro-chemical supplies, but hempcrete has achieved
    popularity in the UK, France and recently the eastern US. I’m led
    to believe that agricultural hemp (non THC) doesn’t require
    fertilizers, herbicides/pesticides. I also seem to recall that an
    acre of hemp has the carbon capturing ability of 4 – 7 acres of
    forest land. It is an ancient totally useful agricultural product.
    Thanks for what you do. Ingo Oevermann

    • Steve, thanks for bringing ocean acidification into the discussion. I hadn’t gone into that, but it’s clearly a key reason why the albedo modification strategy is a poor one. That issue is addressed in the NAS report and is key.


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