Responses to National Academy of Sciences “Climate Intervention” Reports

On February 10, The National Research Council wing of the United States National Academies of Sciences released two reports, Climate Intervention: Carbon Dioxide Removal and Reliable Sequestration, and Climate Intervention: Reflecting Sunlight to Cool Earth (you can find our handy roundup of media coverage of the reports here, our roundup of civil society responses here, and if you have coffee and time at hand, you can find the reports themselves in full here).

Following the release, we sent out a request for short, informal responses to the question:  

“What do these reports mean for your work and the broader climate conversation in your country, and globally?“  

We sought responses from individuals engaged with climate policy and advocacy at all levels, via a range of approaches including human rights, security, environmental justice, ethics and economics.  “We encourage you to respond in any way you see fit, be it critical, dismissive, supportive, or otherwise,” we wrote.

We are pleased to share some of these responses with you.


Miranda Boettcher

They repeat the same trite statements that many before them have made.

Nothing that has been said in the NAS reports is new or innovative. Indeed, reading them, I found myself wondering if the authors had copy-pasted sections of previous reports (Royal Society 2009; GAO 2009; 2011). Basically they repeat the same trite statements that many before them have made; 1) Climate change is a huge problem; 2) Mitigation is the best way to deal with the problem; 3) The international community is unable/unwilling to agree upon adequate mitigation measures; 4) We need to consider alternative options, including climate intervention/engineering measures; 5) We don’t know enough about these measures, so more research is needed to quantify the risks and benefits before decisions on deployment can be made. Nothing new there. However, as discourse analysts and you and I know, sometimes not what is being said, but who is saying it is important. Everyone has experienced it on some level – a bunch of kids at school might be going to a party, but it is only when the cool quarterback decides to go that suddenly everyone starts talking about it. It could be that the NAS is that cool kid who gets everyone to go the climate engineering research party. Of course , a similar analogy can be used to explain why everyone starts smoking just because the cool kids are doing it…

Miranda Boettcher is currently completing her PhD in the field of International Climate Politics at the Heidelberg University, Germany. Her research focuses on the interplay of knowledge, language and power in national and international climate change politics.



Holly Buck

The reports’ drop of the 'geoengineering' signifier is a step in the right direction.

While these reports garnered some criticism for using the term “climate intervention,” this is actually a more accurate and less hubristic term than “geoengineering.” Why is it better? “Intervention” is something that people from all kinds of fields do. The term has use both in medicine / psychology, and in my field, development studies. Using it opens up the idea that we’re not considering how to engineering a natural system, but intervening in a socio-ecological one. Climate change is fundamentally a social problem, one whose signals we are reading in meteorology. A development intervention is a strategy for solving some perceived problem, whether the intervention is to build a road, supply farmers with better information, institute microfinance, or distribute contraceptives. These inherently messy interventions can happen on multiple scales, from the community to the national.

Many of my colleagues consider a development “intervention” to be problematic language.  It evokes a legacy of “developments” where actors from the global North intervened in the economies and social systems of “less developed” countries — often with disastrous results. Plenty of development interventions have been neocolonial, unevenly distributed, or opportunistic. Those dark resonances and histories are important, and can carry lessons for how we think about climate intervention. Take the social problem of energy poverty: distributed solar systems, or hydroelectric mega-projects? Practitioners have wrangled over questions of scale and power in these socio-ecological interventions for decades. Comparing climate interventions to other types of interventions may show us that the promise of the large-scale, global fix is weak compared to small, scalable carbon dioxide removal technologies with social co-benefits. At any rate, the reports’ drop of the “geoengineering” signifier and their switch to language that allows us to better conceptualize coupled and interdependent socio-ecological systems is a step in the right direction for those seeking to think more holistically about the role of technologies in climate, energy, and development.

Holly Jean Buck is a doctoral candidate at Cornell University and a Project Scientist at the Institute for Advanced Sustainability Studies in Potsdam. 


Diesu_round Robby Diesu

If we repeat more of the same- then we have learned nothing.

I think we are at one of the many turning points as we begin to tackle the impacts of Climate Change, and its chaos that humanity will have to endure. We have a choice- we can continue using the same processes and practices that put communities of color and working people at risk, without taking their consent, and continues the cycles of oppression that is inherent in our neoliberal capitalist system.  Or we can use this as a time to take a different approach to look at this as a chance to right the wrongs that have been done- and build the world we need to have to never be in the position again. If we repeat more of the same- then we have learned nothing. “Carbon dioxide removal addresses the root cause of climate change” is a false statement, the root cause of the climate crisis is not CO2 emissions, the roots cause is a economic system run on exploitation and not mutual aid. 

Robby Diesu is a member of the DC Action Lab Collective,  a worker-owned collective of experienced organizers trying to build a world based on equity, justice, and sustainability. He works mostly in the Environmental movement, focusing on brining the voices of communities impacted by Fracking to the national discussion.



 Josh Horton

Meaningful US government support for geoengineering research is overdue.

The NAS reports are important primarily because they represent the most authoritative endorsement of federal support for research into carbon and solar geoengineering yet made in the nascent US debate on climate engineering.  The reports’ findings do not differ fundamentally from findings contained in other high-profile reports released over the past several years, for example the Royal Society’s seminal 2009 reportGeoengineering the Climate.  Similarly, calls for federal funding have been made before by national organizations like the Bipartisan Policy Center.  What sets the NAS reports apart is the potentially great influence that recommendations by the highly-regarded National Academies for national CDR and SRM research programs may have on the US research community, in particular on funding agencies such as the National Science Foundation.  My hope is that these recommendations send a strong signal to federal agencies and programs that significant support for research on geoengineering, by both natural and social scientists, is not just acceptable but encouraged and even urgent.  Meaningful US government support for geoengineering research is overdue, and hopefully the NAS reports will help persuade key decision-makers that it is time to get serious about federal funding.

Joshua Horton is a Postdoctoral Research Fellow with the Science, Technology, and Public Policy Program at the Belfer Center for Science and International Affairs, Harvard Kennedy School. 


Cush_roundCush Ngonzo Luwesi

Using such technologies, African leaders may avoid suicidal climate adaptation strategies.

Global warming is steadily threatening ecosystems and their biological lives across the globe. Though life the equatorial and tropical regions is associated with hot temperatures rather than cooling, the drastic decrease of forest cover and major vegetations in the last century may be an argument for adoption of the principle of large-scale Climate Intervention (also known as Geoengineering) through Carbon dioxide removal (CDR) and albedo modification technologies. African scientists were suspicious about the intention of certain developed countries to use albedo modification as an arm to harm other countries. This fear has been confirmed by the implication of the CIA in funding such a study. The USA apparently had the same fear and would like to explore more alternative uses of these schemes. Moreover, albedo modification technologies may be cheap with effective and quick cooling effects the global climate. However, they may be dangerous, the safest options being expensive or useless. Most African countries would not invest in such “harebrained” schemes, which impacts are certainly negative on their ecosystems. Nonetheless, the report on CDR is very useful, elaborate and interesting to African leaders and scientists because it confirms the usefulness of these technologies, not only for climate mitigation but also energy and food security. Using such technologies, African leaders may supplement their efforts to reduce planned GHG emissions and avoid suicidal climate adaptation strategies. Hence, African countries will likely be very selective when it will come to the ratification of a Climate Intervention Protocol, or agreement.

Dr Cush Ngonzo Luwesi is a lecturer of advanced quantitative techniques and Integrated Watershed Management at the Department of Geography of Kenyatta University.



Mike MacCracken

I wish the reports had made the limitations of mitigation clearer.

The NRC reports on climate intervention will help in important ways. First, the reports make clear that mitigation (i.e., efficiency, alternative technologies, etc.) is essential and that climate intervention is not and cannot be an alternative. I wish, however, that the near-term importance and value of sharply cutting emissions of short-lived species had been made clear rather than focusing all attention on CO2, which accounts for only about half of the augmentation to 21st century radiative forcing from 21st century emissions (that CO2’s forcing carries on for millennia matters, but very disabling impacts will occur much earlier). I also wish the reports had made the limitations of mitigation clearer—keeping global warming below ~2ºC likely requires phasing out global use of fossil fuels by mid-century, and that presently seems far from possible or likely.

Distinguishing the different approaches of carbon dioxide removal (CDR) and albedo modification and proposing more appropriate terminology will be helpful in public communication and policy-making. While CDR would likely have few adverse impacts, CDR will not, in reality, significantly help reduce warming, or even ocean acidification, until mitigation has led to sharp cuts in CO2 emissions—CDR can be an important complement, but not the leading approach.

What was missing was an assessment of the real question, which is whether, assuming realistic mitigation, adaptation and CDR, the various approaches to albedo modification, singly or in combination, have the potential to reduce at least the worst projected impacts and increasing risks of climate change, on a global or even regional (e.g., Arctic) or sectoral (e.g., drought) basis. There are simply too many statements that seem out of context relative to the severe impacts and risks that have convinced the international community to, at least eventually, phase out use of fossil fuels as the world’s primary energy source.

Michael MacCracken, although officially retired, has been serving as Chief Scientist for Climate Change Programs with the Climate Institute in Washington, DC since 2002. After 25 years of research on the climatic effects of natural and human-induced factors at Lawrence Livermore National Laboratory, he served as the first executive director of the Office of the USGCRP and then of its National Assessment Coordination Office.


Matzner_roundNils Matzner

Some reservation seems healthy.

In Germany and Austria the discussion develops under more reservation than in the USA. I am a researcher from Germany working in Austria and as far as I can see the NAS reports was not broadly picked up in both countries. Anyway, there is no research or discussion in Austria on climate engineering. In Germany, the situation is different. It has a research program (SPP 1689), which is oriented towards basic assessment fencing out technology development. At this point, the new reports mean more to the US than some European countries. However, when funding agencies follow the scientist’s call for more research investment, this will have effect on future dynamics. If US-guided “small-scale field experiments with controlled emissions”, as the report suggested will be the next step, further steps are likely to follow. The NAS report addresses problems of risk, uncertainty and governance. Furthermore, they do (slightly) address lock-in problems of R&D, but at the same time research investments increases the risk of an institutional lock-in to climate engineering technologies. One dilemma is, that the report said it is “irrational and irresponsible” to deploy climate engineering now, therefore we need more research. But who is ensuring that further research will prevent future irresponsible deployment? A fully developed technology is likely to be used by someone. I am not sure if we should handle climate engineering with German Angst, but some reservation seems healthy.

Nils Matzner is working in the DFG SPP 1689 on responsibility discourses of CE. He is a STS scholar working now in Austria at the Alpen-Adria University.



Duncan McLaren

The approach reflects ongoing semantic and framing conflicts that obstruct substantive debates.

From my perspective, the committee’s conclusions broadly reflect the current ‘state of the art’ in Europe: extreme caution over SRM (despite an acknowledgement of a case for more research) and growing understanding of the potential of some CDR measures to helpfully complement accelerated mitigation and adaptation in restricting climate risk.

But the committee’s approach also reflects ongoing semantic and framing conflicts that obstruct substantive debates more than they help. Words such as ‘management’ and ‘engineering’ probably do imply more certainty and control than really exists, and could therefore stimulate hubris. But I would argue that we need dialogue that enhances public understanding of the existing and widely used terms in context, rather than calling for new terminology. Such rebranding – however well motivated – typically suggests to the public that there is something to hide.

Moreover, the term ‘climate intervention’ seems poorly considered. It may have very different implications than the committee hope. In Europe for example, ‘intervention’ isn’t loaded with the negative connotations of restricting freedom that it has in some US circles. Worse, using ‘intervention’ risks blurring the important distinctions between mitigation, adaptation and climate geoengineering that the committee was at pains to stress – as all three could be described as ‘interventions’.

Adopting this terminology could actually make it more difficult to advocate for appropriately targeted geoengineering research – especially on CDR – as a complement to mitigation and adaptation, and increase risks that geoengineering will instead be seen by politicians as a (partial) substitute for the accelerated mitigation and increased adaptation humanity urgently needs.

Duncan McLaren researches the justice implications of geoengineering as a part time PhD student at Lancaster, UK; and has advised various research funders and consortia on climate engineering issues.


Nissen_roundJohn Nissen

The reports should have acknowledged the absolute necessity for aggressive CDR.

The reports condone the usual negative attitude to geoengineering by concluding that albedo modification could be too dangerous, CDR could be too expensive, and geoengineering should only be a last resort.

The reports should have acknowledged the absolute necessity for aggressive CDR in addition to emissions reduction, for any chance to keep below 2 degrees warming and avoid dangerous ocean acidification.  This was clear from AR5.

But, more urgently they should have acknowledged the high risk of worsening climate change as Arctic warming accelerates; and they are unhelpful in showing how the immediate requirement for SRM to cool the Arctic can be met.

There is strong and growing evidence to support two hypotheses: (i) that the Arctic warming and sea ice retreat are in a feedback loop, creating a rapid transition of the ocean from an ice-covered, high-albedo state towards a low-ice, low-albedo state; and (ii) the resulting accelerated Arctic warming has, over the past 15 years, caused: a reduction in temperature gradient between tropics and pole; hence a meandering and sticking of the polar jet stream; hence growing weather extremes, crop failure and food insecurity in many countries.  Assuming these hypotheses are correct, we are heading for such a rapidly warming Arctic that catastrophic climate change in the Northern Hemisphere will be unavoidable.

Albedo loss is currently generating around 0.25 petawatt of heating power, averaged annually.  This is growing exponentially so breaking the feedback loop is extremely urgent.  It could require well over 0.25 petawatts of cooling power, necessitating the use of powerful SRM geoengineering techniques, the prime candidates being stratospheric aerosols and marine cloud brightening.  The need for cooling before the sea ice disappears at the end of summer demands full-scale deployment from spring 2015 to minimise risk.

This is indeed a ‘last resort’ situation, where geoengineering has to be used to prevent a catastrophe.  This should have been the main conclusion of the report.

John Nissen is the Chair of the Arctic Methane Emergency Group (AMEG).



Ted Parson

The committee punted on all the hardest and most contentious questions.

The committee got all the important things right: 
–  Never forget that emission cutting and adaptation are first and most important.  
–  But even the best response on these leaves big remaining risks, which call for investigating CDR and albedo modification.  
– These two climate engineering approaches are so different in their potential benefits and risks that they must be considered separately.  
– And expanded research on both should proceed – faster, less encumbered, and more aimed at operational capability for CDR, and with more reservations and (maybe) encumbrances for albedo modification.

Great job, committee!

Beyond these points, the committee punted on all the hardest and most contentious questions, particularly about governance of research – including being quite ambiguous on the hard-fought question of “governance before research.”  My guess is that they will be read, on balance, as saying go ahead and take the next (small) step – to outdoor field experiments including small-scale active aerosol perturbations (both stratospheric and marine cloud brightening).  But plenty of people will parse the text to claim they said the opposite.  It is ambiguous enough to support both readings.

What difference will it make?  They’ve largely affirmed what I took to be a rough consensus from prior discussions, and said little that’s new.  But they’ve provided more depth and authority in the scientific discussion of current approaches, and they’ve pulled together and clarified the debate very nicely – including particularly their terrific summary of current knowledge of the two approaches in the big Tables (3.3 in the CDR report, 3.4 in the AM report).  It’s also important to have the gravity of an NRC committee affirming this stuff and raising its attention.  

It will make a difference if this elevation of prominence is big and sustained enough that it gets research program managers (and their bosses) into a concrete discussion of what specific research to fund, by what criteria, under what (if any) additional oversight and control.   If this happened (which I both expect and hope), it would be a good, careful step forward.  The biggest immediate risk the report raises is that these conversations will proceed exclusively in the United States, rather than immediately engaging foreign counterparts, which is essential to manage longer-term risks.

Ted Parson is Dan and Rae Emmett Professor of Environmental Law and Faculty Co-Director of the Emmett Institute on Climate Change and the Environment at the University of California, Los Angeles.


Salter_roundStephen Salter

I would like to see all the necessary hardware designed and thoroughly tested.

I agree with recommendation 3 that large scale albedo modification should not be deployed at this time but I would like to see all the necessary hardware designed and thoroughly tested.

The two chief methods for albedo modification are the injection of sulphates into the stratosphere and sea salt into the troposphere. The two are very different and people working on marine cloud brightening resent criticism for the less desirable features of the rival proposal.  Salt in the troposphere has no effect on ozone in the stratosphere.  The amount of salt we would need to inject is far below the amount already put into the atmosphere from breaking waves: all we do is to choose the optimum size for nucleation. Most of what we spray will fall back into the ocean.  Any that does come ashore will benefit people with lung problems.  Models show that the effects of marine cloud on precipitation are bi-directional.  There is a good chance that by choosing the places and times for spraying with respect to the phases of monsoons and el-Nino we can reduce both floods and droughts.

Some climate models suggest that stratospheric sulphur may work in the wrong direction for the Arctic, perhaps by reflecting back longwave radiation during the winter.  The short life of tropospheric aerosol means that we have more control of where it goes and when it goes there.

It is quite true that marine cloud brightening will have little effect on ocean acidity beyond a possible reduction in stratification which might reduce concentrations near the surface.  However we should not criticise any proposal which could reduce ocean acidity because it did nothing to preserve Arctic ice.

The report mentions the problems of abrupt termination.  They would not be as immediate as the termination of air traffic control, sewage disposal, electricity generation or telecommunications.  I would be more alarmed by a climate technology which was irreversible.

I would hope that marine cloud brightening would be needed for much less than the millennia mentioned in the report, only until CO2 and methane levels had dropped or there was a general consensus that higher global temperatures were a good thing after all. The next ice age is overdue.

Stephen Salter is emeritus Professor of Engineering Design at the University of  Edinburgh, Scotland.  He has worked on the design of sea-going hardware for Latham’s proposal for marine cloud brightening with tropospheric sea-salt since 2004.


Sclove_roundRichard Sclove

I believe that proceeding with further research on climate engineering is premature.

The prospect of geoengineering the earth’s climate raises deeply troubling issues, as the authors of the two new NRC reports understand. However, especially in the context of issues with global dimensions, more scientific and engineering research and understanding is not automatically beneficial. There is, for instance, a danger that improved knowledge of how to implement macro-scale geoengineering will inadvertently build social momentum for actually doing so, even if the risks and benefits and their distribution remain contested. Or suppose that better understanding is developed of which areas of the globe or social sectors of societies are most likely to benefit from geoengineering, and, conversely, of which run the greatest risks of being harmed. Without prior international agreement on:∗ whether to conduct geoengineering research, ∗ on what terms, ∗ who will have, and not have, the authority to act on the basis of research results, and∗ a regime for enforcing the terms of such agreements there is a danger that nations or other actors identified as likely beneficiaries will take unilateral action with potentially unfair or even calamitous impacts on others. On such bases I believe that proceeding with further scientific and engineering research on climate engineering is premature and societally riskier than the NRC study acknowledges. At this point a more promising and ethical next step would be to support social scientific and ethical research on the practical implications of conducting – or not conducting – scientific and engineering research on geoengineering the earth’s climate. This social scientific and ethical research ought furthermore to be complemented by multinational citizen deliberations addressed to the question of whether or not further scientific and engineering research on geoengineering is ethically acceptable and warranted. (For one example of a global citizen-deliberation model, see This is information that political decision-makers need before deciding whether to support further scientific and engineering research.

Richard Sclove, Ph.D. is founder and Senior Fellow of the nonprofit Loka Institute, and a cofounder of the Expert and Citizen Assessment of Science and Technology (ECAST) network. He is the author of the book Democracy and Technology and of Reinventing Technology


noavatarRobert Tulip

I disagree with the NAS headline claim that CDR is not a substitute for emission reduction.

I warmly welcome interest in research development and deployment of carbon dioxide reduction technology.  I have developed concepts for large scale ocean based algae production systems which got to the finals of an MIT Climate CoLab competition, but the lack of any discussion has really perturbed me.
I disagree with the NAS headline claim that CDR is not a substitute for emission reduction.  This substitution question should not be a taboo or assumption, but should be subject of careful analysis.  I believe that algae production can fix twice as much carbon as total emissions within the next decade.  This would set the platform for energy majors and the US military to engage constructively, enabling ongoing fossil fuel extraction alongside rapid moves to stabilise the climate.

Robert Tulip manages aid programs in the energy and resources sector for the Australian Government Department of Foreign Affairs and Trade.  His comments on climate are personal views and are not made in my official capacity.