The Evolution of Climate Engineering Research (Opinion Article)

Lawrence and Crutzen (2013) – The Evolution of Climate Engineering Research – Click for download

Screen Shot 2013-07-01 at 3.25.30 PMIntroduction

The emerging climate engineering (CE) debate will be fed by scientific information – and likely by mis-information as well.  This leaves us with the question: how has the scientific discourse around CE evolved?  And how will it likely evolve in the coming years? Until recently, only a very limited number of scientists ventured to seriously investigate climate engineering, and this research has been predominately theoretical, mostly with computer simulations.  No field tests of continental- or global-scale CE have been carried out to date, rather only small-scale tests of various aspects of CE, such as carbon dioxide (CO2) uptake by phytoplankton, underground CO2 sequestration, and brightening of marine clouds.

Here, we would like to present a scientists’ perspective of the evolution of CE research.  In doing so, out of the various developments over the past few decades, we have chosen to focus in on three major topics which have been instrumental in driving the recent evolution and setting the stage for further developments: 1) ocean (iron) fertilization, 2) the set of articles published together in Climatic Change in 2006 on stratospheric sulfate injections, and 3) the advent of coordinated modeling activities to study climate engineering. These topics, especially the first one relative to the latter two, are a bit disconnected; this reflects the current activities in this field, which cover a very broad range of proposed CE techniques, and which has no form of international coordination or top-down organization. Following this, we will also give an outlook to how climate engineering research might continue to evolve.  Although these selected topics are mostly focused on natural science aspects, some of them touch on social, philosophical and governance aspects, and we would like to emphasize up front that these interdisciplinary aspects have been and will remain crucial to the overall discourse.

Ocean (Iron) Fertilization

The first intense, international studies of any type of CE began in the early 1990s with ocean iron fertilization (OIF), a method associated with the Carbon Dioxide Removal (CDR) branch of CE techniques.[1]: There have now been large international research projects on the topic, which included over a dozen ocean iron fertilization experiments between 1990 and 2009, numerous supporting studies with numerical models, and even a few companies that grew rapidly based on speculative sales of carbon credits on the voluntary market; a detailed overview of the scientific developments in the field of OIF over the past two decades is available in Williamson et al. 2012,[2] and an overview of the activities of the commercial interests that have been involved in trying to develop or prepare the pathway for marketing OIF techniques is given in  Eli Kinitsch’s book “Hack the Planet”.[3]

The research on ocean iron fertilization has provided a very mixed picture of the effectiveness of carbon drawdown and sequestration into the deep ocean. However, a few points have become generally clear. First, ocean fertilization can apparently very effectively increase the downward flux of carbon under some conditions, and fail completely under other conditions; there are many complexities that are not well understood. Moreover, quantifying the actual amount of post-fertilization deep-ocean sequestration is generally extremely challenging and highly uncertain, though possible under some limited oceanic conditions. Finally, the plankton blooms are very likely to be accompanied by substantial undesired side effects on the marine environment and the atmosphere.

The ocean fertilization experiments and analyses led to discussions by scientists and stakeholders about not only the environmental advantages and disadvantages, but also about political and ethical concerns.  Until recently, there was no legal framework for regulating ocean fertilization.  In the mid-2000s, efforts were begun to better connect the natural science analyses with other disciplines, especially law, as well as with the practitioner’s perspective from the side of policy advice, in order to help better place the scientific results into a language that would be more supportive of the development of policy measures.[4] Along with pressure from NGOs, the first such interdisciplinary analyses helped lead to a resolution in 2008 by the London Convention and Protocol[5] prohibiting ocean fertilization for commercial purposes, but allowing approved, basic science experiments, subject to a relatively restrictive assessment framework for environmental impacts.  Among all the proposed CE techniques, ocean fertilization was the first, and is still the only one, which in principle has a basic regulatory framework for research and implementation.  However, the effectiveness and enforceability of this framework is now being put to the test, following a covert implementation of iron fertilization off the coast of Canada in the summer of 2012, for which legal action is currently being investigated.[6]

Articles published in Climatic Change in 2006

The research on OIF over the last two decades, both in terms of field experiments and computer model simulations, have demonstrated that there was no broad taboo in the scientific community against scientifically investigating ocean fertilization. Quite the opposite was the case for the other form of CE, “solar radiation management” (SRM).[7] This taboo became very apparent in the discussions around an editorial essay about SRM using stratospheric sulfate aerosols published by Paul Crutzen in 2006,[8] along with five commentaries published together in the same issue.[9]  Extensive, harsh criticism was expressed by many members of the community, centered around two main concerns. First, SRM schemes neither address CO2 emissions nor other environmental impacts such as ocean acidification, and might thus detract from these serious concerns. Second, there may be a “moral hazard”, in that researching SRM may unintentionally help to legitimize it, raising hopes that there will be an alternate “quick fix” solution to climate change, and thereby derailing the efforts to reduce CO2 emissions.

Attention to these concerns resulted in careful statements being included in Crutzen (2006), indicating the caution needed in considering climate engineering, including a discussion of the possible side effects, and the many scientific, legal, ethical, and societal issues, and finally noting that “…the albedo enhancement scheme should only be deployed when there are proven net advantages and in particular when rapid climate warming is developing, paradoxically, in part due to improvements in worldwide air quality.” This cautious encouragement of research was also reflected in nearly all of the five invited commentaries published alongside Crutzen (2006).  The experiences with OIF noted in the previous section were very influential in leading to this encouragement as stated in Lawrence (2006), especially having recognized how a good scientific knowledge base was important in the support of and eventual formulation of a resolution on governing OIF.  It is, however, unclear if that was an important motivation in the other calls for research, and it is also unclear whether this conclusion can really be applied to other types of CE (determining that would be an extensive research project in and of itself).

After the publication of Crutzen (2006) and the commentaries, the openness of the community towards research on SRM changed rapidly.  Prior to 2006, there were only a very limited number of studies of SRM, and the core climate modelling community around the CMIP (IPCC) simulations had not yet addressed it in their models.  In the half decade since then there have already been numerous publications looking at various aspects of climate engineering using models, with many scientists being motivated by the recognition that “…geoengineering is being discussed intensely, at least outside of the formal scientific literature, and it is not going to go away by ignoring it or refusing to discuss it scientifically”.[10]  One of the most important highlights of lifting the taboo on SRM research is that there are now substantial efforts to coordinate community-wide simulations with multiple models.

Community-wide Multi-model Studies

The first publications on climate engineering were single model studies of various aspects of various CE techniques, for instance the global distribution of the effect of turning down the solar constant, or determining the amount of stratospheric sulfur injection that would be needed to produce a certain radiative forcing and what this would imply for changes in the ozone layer.  These resulted in a rather mixed picture, with little clarity as to which results from which models to trust, or in many cases, how to even compare the results from different setups of studies.  Nevertheless, despite the uncertainty in models, they are the tool that currently needs to be relied on to gain an initial impression of the potential effectiveness and side effects of various proposed CE techniques; field tests are limited in terms of the information they could give, since at small scale it is unclear how they would scale up given the vast heterogeneity in the global Earth System, and at a scale large enough to be confident in the scaling the field “tests” would have more of the character of a small-scale implementation. A major step forward to help reduce the uncertainty in the analyses of the model simulations has recently been taken by two projects, IMPLICC[11] and GeoMIP.[12] The two projects decided to use the same main scenarios for stratospheric sulfur injections and solar constant modifications (emulating mirrors in space) for their simulations.  The IMPLICC and GeoMIP simulations[13] build on the simulations of CMIP5 (Coupled Model Intercomparison Project, 5th generation) for the IPCC Fifth Assessment Report.  In that sense, these multi-model projects generally rely on the climate and Earth System models in the form that they are available and used for the CMIP5 simulations; IMPLICC and GeoMIP have contributed to understanding how to set up useful CE simulations that are comparable across a wide array of models, and to improving on the robustness in the interpretation of the model results, as well as the sense of uncertainty in these results, but the projects are not contributing significantly to the development or improvement of the models themselves.  IMPLICC has moved ahead first with its three core models, and also includes additional scenarios for marine cloud brightening.  A first paper, including a fourth model from GeoMIP, has already been published.[14]  GeoMIP will have a wider participation, and give a much clearer and more robust view than previous studies of CE, with papers for a first special issue of the Journal of Geophysical Research – Atmospheres currently under review.

Outlook – How Will Climate Engineering Science Evolve Further?

While a major part of the future evolution of CE research will extend on some of the trajectories outlined above, especially the expansion of community-wide multi-model studies, a highly uncertain direction of development involves future field-testing of CE.  The field tests of ocean fertilization were discussed above; there is now a great debate in the scientific community as well as between civil society organizations and various researchers regarding field-testing of SRM. Without singling out members of the community here, it has become evident that there are several who contend that it is necessary to have field tests in order to get beyond the uncertainties in models, while others claim it is far too premature and may lead to a backlash, potentially even inhibiting future research of other climate-relevant processes like cloud microphysics, which could be mistakenly perceived as being done in relation to CE.  Generally, governance of CE research distinct from other, non-CE basic research will face the challenge that these will often be difficult to distinguish from each other in terms of the forms in which they are carried out, and intention (i.e., whether for the purpose of developing an understanding of CE or not) is even more difficult to determine and distinguish .

Beyond the natural science research which has been the focus here, two extremely important further developments are underway: first, the effort to connect across the various disciplines involved in understanding CE, including the natural sciences, economics, psychology, philosophy, political sciences and law; and second, the challenge of “trans-disciplinary” research, the co-generation of knowledge by researchers and stakeholders.  Many CE studies have already been published in the separate disciplines, with only a few interdisciplinary studies so far, and even less trans-disciplinary work.  However, substantial efforts are being made at building these bridges between the disciplines and between researchers and stakeholders, in particular through several large projects such as “EuTRACE” that have been set up over the last few years to take on this challenge.[15]  This will be especially relevant in leading to sensible governance – which is also likely to include governance of the scientific research itself as the field continues to evolve.

The primary message we have hoped to bring out here is that research on climate engineering is evolving extremely rapidly, and while some developments can be foreseen, it is extremely difficult to know how this research will impact policy development, and especially how it can be targeted to effectively inform the social dialogue around CE, without risking derailing the basic efforts towards mitigation and adaptation measures.  Because of the importance of carrying out research on CE in an effective and responsible manner, as well as a larger context of global efforts towards sustainable development, a deeper understanding of the evolution and future pathways of CE research is needed.


Bengtsson, L. 2006. “Geo-Engineering to Confine Climate Change: Is it At All Feasible?” Climatic Change 77 (3-4): 229-234.

Cicerone, R.J. 2006. “Geoengineering: Encouraging Research and Overseeing Implementation.” Climatic Change 77 (3-4): 221-226.

Crutzen, P.J. 2006. “Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolve a Policy Dilemma?” Climatic Change 77 (3-4): 211-219.

Fountain, H. 2012. “A Rogue Climate Experiment Outrages Scientists.” New York Times. Published 18 October. Available at:, accessed 22 June 2013.

Kiehl, J.T. 2006. “Geoengineering Climate Change: Treating the Symptom Over the Cause?” Climatic Change 77 (3-4): 227-228.

Kintisch, E. 2010. Hack the Planet: Science’s Best Hope – or Worst Nightmare – For Averting Climate Catastrophe. New Jersey: John Wiley and Sons.

Kravitz, B., A. Robock, O. Boucher, H. Schmidt, K.E. Taylor, G. Stenchikov, and M. Schulz. “The Geoengineering Model Intercomparison Project (GeoMIP).” Atmospheric Science Letters 12(2): 162-167.

Lawrence, M.G. 2006. “The Geoengineering Dilemma: To Speak or Not to Speak.” Climatic Change 77 (3-4): 245-248.

MacCracken, M.C. 2006. “Geoengineering: Worthy of Cautious Evaluation?” Climatic Change 77 (3-4): 235-243.

Rayfuse, R., M.G. Lawrence, and K.M Gjerde. 2008. “Ocean Fertilization and Climate Change: The Need to Regulate Emerging High Seas Uses.” The International Journal of Marine and Coastal Law 23(2): 297-326.

Schmidt, H., K. Alterskjaer, D. Bou Karam, O. Boucher, A. Jones, J.E. Kristjansson, U. Niemeier, M. Schulz, A. Aaheim. F. Benduhn, M. Lawrence, and C. Timmreck. 2012. “Solar Irradiance Reduction to Counteract Radiative Forcing from a Quadrupling of CO2: Climate Responses Simulated by Four Earth System Models.” Earth System Dynamics 3: 63-78.

Shepherd, J., K. Caldeira, P. Cox, J. Haigh, D. Keith, B. Launder, G. Mace, G. MacKerron, J. Pyle, S. Rayner, C. Redgwell and A. Watson. 2009. Geoengineering the Climate: Science, Governance and Uncertainty. London: Royal Society.

Williamson P., D.W.R. Wallace, C.S. Law, P.W. Boyd, Y. Collos, P. Croot, K. Denman, U. Riebesell, S. Takeda, and C. Vivian. 2012. “Ocean Fertilization for Geoengineering: A Review of Effectiveness, Environmental Impacts and Emerging Governance.” Process Safety and Environmental Protection 90(6): 475-488.

[1] OIF is the idea that enhancing growth of phytoplankton in the oceans (e.g., by fertilizing with iron or other nutrients) would cause them to draw down additional CO2 from the atmosphere for photosynthesis, locking up the carbon in biomass, some of which will sink to the deep oceans following death or ingestion and excretion.

[2] Williamson et al. 2012

[3] Kintisch 2010

[4] Rayfuse et al. 2008

[5] The London C/P is the international maritime convention regulating the dumping of waste in the ocean.

[6] For a representative media account, see Fountain 2012 in the NY times.

[7] While CDR methods attempt to absorb and sequester carbon from the atmosphere, SRM seeks to cool the climate by increasing the reflection of sunlight in various ways. See Shepherd et al. 2009.

[8] Crutzen 2006

[9] Cicerone 2006, Kiehl 2006, Bengtsson 2006, MacCracken 2006, Lawrence 2006

[10] Lawrence 2006

[11] “Implications and Risks of Engineering Solar Radiation to Limit Climate Change”,

[12] “Geoengineering Model Intercomparison Project”,

[13] Kravitz et al. 2011

[14] Schmidt et al. 2012

[15] The European Trans-disciplinary Assessment of Climate Engineering” (EuTRACE) brings together 14 partner organizations in Europe, with personnel from across the natural and social sciences, to assess climate engineering. See:

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One response to “The Evolution of Climate Engineering Research (Opinion Article)

  1. These distinguished authors delivered what they promised: a scientist’s perspective on the evolution of climate engineering research. But science it not the only driver here, and the article fails to include absolutely essential legal, historical, and ethical considerations involved in any attempt to terraform a planet inhabited by over 7 billion people. They write, “The emerging climate engineering (CE) debate will be fed by scientific information…” But this is surely only part of a healthy diet that must include social and cultural considerations as well.

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