Not long ago, climate engineering, often called geoengineering, was a dirty word in environmental circles, for it not only connoted directly tinkering with the atmosphere but also conjured up moral hazard: why suffer the cost of reducing carbon emissions now if we can rely later on technology to reverse global warning?
By Gregory F. Treverton
NOTE: The views expressed here are those of the author and do not necessarily represent or reflect the views of SMA, Inc.
Alas, what has changed is reality: it is now clear that there is no way the world will meet the Paris targets of no more than a 1.5°C increase in temperature. That was the conclusion of last December’s climate summit, which, true to form, the Trump administration did not attend. Ready or not, climate engineering (CE) is coming, and the United States should aim to be ready for it.
There are two broad families of CE technology: carbon dioxide reduction (CDR) and diminishing solar incidence, often referred to as solar radiation management (SRM), which includes stratospheric aerosol injection (SAI), marine cloud brightening, and airborne mirrors. The various methods are laid out and assessed in Table 1. As rocks weather, they extract carbon from the atmosphere; a variety of techniques could enhance that effect. Direct capture uses chemical processes that mimic trees. Ocean fertilization inserts iron or other nutrients to speed the growth of plankton blooms that absorb carbon. CDR is to be preferred, for it not only could reduce temperature but also would diminish other effects of carbon build-up, like eroding coral reefs. Unfortunately, what is possible, capturing carbon by fertilizing oceans, is slow; what would be better, capturing carbon directly from the atmosphere, remains too expensive.
So SRM will be the immediate focus of attention. Cloud whitening injects salt water into clouds to make them more reflective. SAI would mimic the effect of major volcano eruptions by injecting sulfur dioxide into the stratosphere, where it would reflect sunlight. Space-based mirrors would do the same, very expensively but with fewer side-effects.
Table 1: Rough Assessments of Climate Engineering Methods
|Marine cloud brightening||Medium to high||Medium||High||Medium|
|Sulphur aerosol injections||High||High||Low||Low|
|Space-based mirrors||High||Very low||Medium||High to very high|
|Enhanced weathering||High||Low||Medium to high||High|
|Direct capture||High||Low||Very high||High|
|Ocean fertilization||Low||Low to very low||Very low||Medium|
As the table suggests, SRM, especially injecting aerosol, is both effective and relatively cheap. The rub is the uncertainty about unintended—and perhaps as yet unknown—side-effects, perhaps most prominent among them effects on the ozone layer. Thus, careful global monitoring is in order for climate engineering projects that nation states, industry, and/or non-governmental organizations (NGOs) might deploy, along with an assessment of the risks and ethical considerations associated with those deployments.
The uncertainties about CE are legion:
- Technology—relative motivations for different technologies; performance of technologies; physical and temporal scales of impacts; unintended consequences, etc.
- Governance—standards, regulations, and/or agreements and their effectiveness; public vs. private control over technology.
- Data—quality, availability, coverage, sharing.
- Deployment—context (crisis vs. non-crisis vs. malevolent, public acceptance, economics, winners and losers).
- Climate conditions/goals—climate conditions at time of deployment.
- Normative goals—human security, social justice and equity, national security. In the end, what are the national security implications of CE, both agreed and nefarious?
The other big question is unilateral CE, which might be done by a range of actors from desperate states to proof-of-concept private entrepreneurs. That range is laid out in table 2. In general, unilateral CE does not look very promising, for of the techniques, only cloud brightening (and mirrors, were they affordable) have relatively localized effects. For example, when Mt. Pinatubo erupted, it took several months for the sulfates it put in the stratosphere to spread worldwide pole-to-pole, and those stayed up about two years. Direct carbon capture suffers in spades from the same free-riding from the same defect as reducing carbon emissions: everyone would like everyone else to do it, so they can enjoy the benefits without the costs.
That said, while the United States and its allies have programs relevant to climate engineering, it is worth asking whether—just as the “nuclear (power) renaissance” that wasn’t in the West but was in authoritarian countries—deployment of CE, especially unilateral, will be more likely from authoritarian regimes rather than the democracies. Just as dirty and ethically controversial science and production move offshore to escape regulation, the same may be the case for CE.
So, too, moral hazard will remain if, for example, the rise of carbon “cap and trade” mechanisms induces less scrupulous governments to see value in protecting dirty industries such as coal by engaging in climate engineering, perhaps in a regional way. Much will depend on how localized “local” is in atmospheric phenomena. The prospect of China using aerosols to compensate for coal, but affecting monsoons in South Asia in the process, is not a happy outcome.
Table 2. Possible Unilateral CE
|Actor||OF, short term||OF, long term||SAI, short term||SAI, long term|
|Great powers||Possible for creating leverage in international climate diplomacy||Possible as a long-term mitigation measure||Possible in response to a climatic emergency||Possible in response to a climatic emergency|
|Small states||Not possible, lack of incentives and interference likely||Possible as a long-term mitigation measure but depends on international response||Not possible, lack of delivery systems/ geographical access; cost constraints||Possible in response to a climatic emergency if delivery systems are available and no-fly zones cannot be enforced|
|Non-state actors||Not possible, lack of incentives and interference likely||Possible if carbon prices increase and regulatory environment changes, but depends on international response||Not possible, lack of delivery systems/ geographical access; cost constraints||Possible for demonstrating the technology’s commercial value/safety if delivery systems are available and national authorities do not interfere|
CE is a classic case where the precautionary principle applies: extra caution is warranted when confronting low probability/high consequence possibilities. Lab research will never be sufficient to persuade democracies to commit to anything risky without some field experiments. The question is, “How to do climate engineering field experiments without impacting the climate?”
All these are arguments for thinking now about CE. A first step is trying to improve the science and reduce the uncertainties about effects, both intended and unintended. A second is putting in place arrangements, ideally international, to be on the look-out for unilateral CE. A third, and critical, is beginning to work on agreements about cooperative CE now, not waiting for a spike in global temperatures that seems to compel immediate—but probably hasty—SAI or other CE. Happily, the Biden administration is committed to action on the climate crisis. For better or worse, CE is now part of that agenda.
 Climate engineering (CE) is intentional, large scale intervention in the earth’s climate system to counter the effects of climate change. Climate engineering is often referred to as geoengineering, though the latter might be broader, including, for example, issues such as water and agriculture that relate to climate but are a different focus.
 This article draws on work I have been doing for the Sandia National Laboratories. None of my good colleagues in that work should, however, be implicated in anything I say here.
 Adapted from Bodansky, Daniel. “Governing Climate Engineering: Scenarios for Analysis” Discussion Paper 2011-47, Cambridge, Mass.: Harvard Project on Climate Agreements, November 2011, available at www.belfercenter.org/sites/default/files/legacy/files/bodansky-dp-47-nov-final.pdf.
 For example, the NAS benchmark report on SRM released in 2015, has been followed by a study on governance and research needs for climate intervention strategies that reflect sunlight to cool the Earth, due to be published in Fall 2020. www.nationalacademies.org/our-work/developing-a-research-agenda-and-research-governance-approaches-for-climate-intervention-strategies-that-reflect-sunlight-to-cool-earth. International NGO and civil society organizations, such as the Solar Radiation Management Governance Initiative (SRMGI) are engaged in building capacity of developing countries to evaluate SRM. Also see, Wanser, Kelly (2020), “Climate Intervention Research May be Critical to a More Just and Safe Society”, published during United Nations Climate Week 2020 at medium.com/@kellywanser/climate-intervention-research-may-be-critical-to-a-more-just-and-safe-society-2046a2095dc8; Amelung, D. and J. Funke (2015). “Laypeople’s Risky Decisions in the Climate Change Context: Climate Engineering as a Risk-Defusing Strategy?” Human and Ecological Risk Assessment: An International Journal 21(2): 533-559.; Bodansky, D. (2013). “The who, what, and wherefore of geoengineering governance.” Climatic Change 121(3): 539-551; Holahan, R. and P. Kashwan (2019). “Disentangling the rhetoric of public goods from their externalities: The case of climate engineering.” Global Transitions 1: 132-140.
 See C. Hamilton, Earth Masters: The Dawn of The Age of Climate Engineering, Yale University Press, 2013, p. 67.