Climate engineering: a cause for hope - or a reason to fear?

Philosophical Transactions of the Royal Society A

Climate Engineering: Exploring Nuances and Consequences of Deliberately Altering the Earth’s Energy Budget

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Image by Alan L

In the light of the steady, unrelenting rise in the concentration of carbon dioxide in the Earth’s atmosphere leading to global warming, Climate Engineering (CE) has been proposed to limit the rise in our planet’s temperature. This theme issue of Philosophical Transactions of the Royal Society A* examines some of the challenges linked with the application of three strategies for CE. These strategies modify the Earth’s radiation budget, and produce global and regional impacts, the latter being especially important for critically sensitive regions such as the Arctic.

Three strategies are considered: (1) increasing Stratospheric Sulphur Particles to mimic the effects of volcanic eruptions, reflecting more sunlight back into space; (2), Marine Cloud Brightening, in which low-level oceanic clouds are seeded with salt particles from evaporated sea-water to increase cloud droplet numbers, making them reflect more sunlight; (3) Cirrus Seeding, which causes the highest atmospheric clouds to thin, facilitating the emission of heat/energy from the Earth’s surface.

This volume explores scientific and engineering issues connected to the three methods, describes possible field experiments that can be used to improve understanding of those processes, and examines societal issues associated with the testing of CE and its impact on the planet.

Research includes: A paper exploring the ethics of reducing efforts to mitigate climate change in response to the prospect of climate engineering research; a study that finds that geoengineering is likely to pose a moral hazard for some more than others; and papers exploring technologies including cloud seeding, cloud brightening, and solar radiation management.

Please note that both the media summaries and the journal issue itself represent the views of the authors and not the position of the Royal Society.

Climate Engineering: Exploring nuances and consequences of deliberately altering the Earth’s energy budget

By Latham, John; Rasch, Philip; Launder, Brian

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0050

Introduction to issue. Contact: Dr John Latham, National Center for Atmospheric Research, johnlathamgh@gmail.com

Ethical aspects of the mitigation obstruction argument against climate engineering research

By Morrow, David

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0062

Many people fear that researching climate engineering will undermine efforts to reduce greenhouse gas emissions. Some people have used this so-called “moral hazard” problem as an argument against further climate engineering research. This paper explores the ethics of reducing mitigation efforts in response to the prospect of climate engineering research. The paper argues that even if climate engineering might justify some reductions in mitigation, there is a serious risk that policymakers would replace mitigation with climate engineering in morally objectionable ways. At this point, however, it is virtually impossible to know whether climate engineering research would make the world worse off. Climate engineering research is therefore a moral gamble. Contact: Dr David Morrow, University of Alabama at Birmingham, davidmorrow@uab.edu

Geoengineering, climate change scepticism and the ‘moral hazard’ argument: An experimental study of UK public perceptions

By Corner, Adam; Pidgeon, Nick

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0063

Will the prospect of geoengineering reduce public support for existing policies to cut carbon emissions? This question is at the heart of the debate about this controversial set of new technologies. In this paper we provide the first systematic evidence of public attitudes towards the ‘moral hazard’ argument against geoenginering. Strikingly, we found that geoengineering is likely to pose a moral hazard for some more than others. People who are wealthier, more ‘self-interested’, and who are sceptical about climate change were more likely to agree that the prospect of geoengineering would reduce their motivation to engage in sustainable behaviours. Contact: Prof. Adam Corner, Cardiff University, corneraj@cardiff.ac.uk

Governing solar geoengineering research as it leaves the laboratory

By Parker, Andrew

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0173

Concerns over the potential risks of solar geoengineering research have led many experts to call for experiments to be delayed until suitable governance arrangements are established, typically through international agreement. This paper explores that call, and concludes that a delay in research – a moratorium – is not likely to be feasible, and probably is not the best way to manage geoengineering research risks. Instead researchers and research funders should take the lead in developing good governance practices, ‘learning by doing’ small scale experiments that are safe and informative. Contact: Mr Andrew Parker, Harvard Kennedy School, aparker1@gmail.com

Mapping the landscape of climate engineering

By Oldham, Paul; Szerszynski, Bronislaw; Stilgoe, Jack; Brown, Calum; Eacott, Bella; Yuille, Andy

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0065

Climate engineering, also called geoengineering, is the large scale, intentional manipulation of the earth’s climate system to counteract anthropogenic climate change.  While at this stage it is merely a prospective technology, and a controversial one, in recent years there has been a rapid growth in scientific research into its feasibility, and in patent claims for particular climate engineering technologies. This article uses bibliometric techniques to explore publications and patenting in climate engineering in order to make visible the way the field is growing, and the emergence of key clusters of institutions, individuals and funders involved in research and intellectual property. Contact: Dr Bronislaw Szerszynski, Lancaster University, bron@lancaster.ac.uk

Asilomar Moments: Formative Framings in Recombinant DNA and Solar Climate Engineering Research Governance

By Schäfer, Stefan; Low, Sean

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0064

In contrast to research on recombinant DNA technology, where risks came to be defined on a purely technical basis, concerns regarding solar climate engineering span from physical risks to ethical, political, social, economic and cultural issues. To account for this, even small scale field tests with negligible impacts on the physical environment require some additional governance beyond what already exists. Contact: Mr Stefan Schäfer, Institute for Advanced Sustainability Studies, Stefan.Schaefer@iass-potsdam.de

Modelling artificial sea salt emission at a cloud resolving scale

By Maalick, Zubair; Korhonen, Hannele; Kokkola, Harri; Kühn, Thomas; Romakkaniemi, Sami

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0051

Marine stratocumulus cloud brightening (MCB) is considered to be one of the potential geoengineering methodologies to counteract the global warming. Understanding of how different aerosol processes affect particle dispersion is crucial when designing emission sources, and here the dispersion of sea salt particles from artificially injected sea spray is studied at a cloud resolving scale with an explicit treatment of aerosol water, which takes into account condensation, evaporation and their effect on ambient temperature. Water evaporation causes delay in aerosol transport to boundary layer which enhances the particle scavenging in emission layers and decreases the efficacy of proposed method. Contact: Mr Zubair Maalick, University of eastern finland, zubairm@uef.fi

Process-model simulations of cloud albedo enhancement by aerosols in the Arctic

By Kravitz, Ben; Wang, Hailong; Rasch, Philip; Morrison, Hugh; Solomon, Amy

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0052

Many previous studies have evaluated marine cloud brightening from both global and process modeling perspectives.  All prior process model studies of marine cloud brightening were restricted to warm clouds.  Our study is the first process modeling study to evaluate the effects of aerosol injection into mixed phase clouds.  We have developed a modified microphysical scheme that can account for ice nucleation and growth.  Our results show that marine cloud brightening in mixed phase clouds is dominated by albedo increases in the liquid phase.  Evidence for the first and second aerosol indirect effects is apparent. Contact: Dr Ben Kravitz, Pacific Northwest National Laboratory,ben.kravitz@pnnl.gov

Marine Cloud Brightening: Regional Applications

BY Latham, John; Fournier, Jim; Wadhams, Peter; Parkes, Ben; Gadian, Alan

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0053

The general principle behind the Marine Cloud Brightening (MCB) climate engineering technique is that seeding marine stratocumulus clouds with substantial concentrations of roughly mono-disperse sub-micrometre sized sea-water particles might significantly enhance cloud albedo and longevity, thereby producing a cooling effect. This paper is concerned with preliminary studies of the possible beneficial application of MCB to three regional issues: (1), recovery of polar ice loss; (2), weakening of developing hurricanes; and (3), elimination or reduction of coral bleaching. Contact: Dr John Latham, National Center for Atmospheric Research, johnlathamgh@gmail.com

Preliminary results for salt aerosol production intended for marine cloud brightening, using effervescent spray atomization

By Cooper, Gary; Foster, Jack; Galbraith, Lee; Jain, Sudhanshu; Neukermans, Armand; Ormond, Bob

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0055

A variant of an industrial atomization technique, using only compressed air and saltwater, has been used to create salt nuclei in a size range deemed suitable for marine cloud brightening, a geoengineering technique that is favored for its low environmental impact.  This would make it possible for scientists to test the method on a very limited experimental basis.  The salt nuclei would be lifted with equipment similar to snow-making machines, from ocean-going ships, to reach low-hanging clouds where they would convert into droplets thereby enhancing cloud reflectivity and cooling the earth. Contact: Dr Gary Cooper, FICER, ranchcoop@gmail.com

Factors determining the most efficient spray distribution for marine cloud brightening

By Connolly, Paul; McFiggans, Gordon; Wood, Rob; Tsiamis, Andreas

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0056

Marine Cloud Brightening is a geoengineering method proposed to mitigate rising temperatures in a changing climate. It relies on generating a fine mist of salt particles from sea water to increase the amount of sunlight that clouds reflect. Previous studies have optimized the salt particle sizes to produce the largest increase in cloud reflectance neglecting the important consideration of energy. Our paper optimizes the salt particle sizes to produce the required change in cloud reflectance for the least energy cost. It is newsworthy because it assesses the practicality of a technology aiming to offset rising temperatures. Contact: Dr Paul Connolly, University of Manchester,p.connolly@manchester.ac.uk

Solar geoengineering to limit the rate of temperature change

By MacMartin, Douglas; Caldeira, Ken; Keith, David

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0134

One of the criticisms levelled at using "solar geoengineering" to offset some fraction of climate change is that once started, it would need to be used (practically) forever.  However, this is only true if it was used to keep global mean temperatures roughly constant, as has generally been assumed.  If solar geoengineering were instead used only to slow down the rate of climate change, many impacts of climate change would still be reduced, but only a temporary deployment would be required.  This would also require less solar reduction, lowering risks from deployment.  Implicit assumptions about its use thus impact perceptions of risk regarding geoengineering.  Continued greenhouse-gas emissions would still result in a need for longer geoengineering deployment, underscoring the importance of mitigation. Contact: Dr Douglas MacMartin, California Institute of Technology, macmardg@cds.caltech.edu

Stratospheric controlled perturbation experiment (SCoPEx): a small-scale experiment to improve understanding of the risks of solar geoengineering

By Dykema, John; Keith, David; Weisenstein, Debra; Anderson, James

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0059

The Stratospheric Controlled Perturbation Experiment (SCoPEx) is an experiment under development that will provide the capability, under external oversight, to do controlled micro-scale experiments in the stratosphere. These experiments offer a direct and disciplined pathway to improve our knowledge of the risks and efficacy of solar radiation management through stratospheric aerosol methods. While laboratory experimentation can improve the current state of knowledge and atmospheric models can assess large-scale climate response, these approaches cannot represent the full range of interactive atmospheric chemical physics. Small-scale, in situ experimentation under well-regulated circumstances can begin to remove some of these uncertainties. Contact: Dr John Dykema, Harvard University, dykema@huarp.harvard.edu

Cirrus cloud seeding – A climate engineering mechanism with reduced side effects?

By Storelvmo, Trude; Boos, William; Herger, Nadja

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0116

We present the first coupled atmosphere-ocean model simulations of the climate response to cirrus seeding, and find that this climate engineering mechanism can cool the planet by as much as 1.4K. The cooling is most pronounced at high latitudes, and is accompanied by only a modest reduction in global mean rainfall and an overall pattern of “wet gets drier, dry gets wetter”. This climate engineering mechanism avoids many of the caveats that are associated with solar radiation management, for example delayed recovery of the ozone hole or drastic changes to the global hydrological cycle. Contact: Dr Trude Storelvmo, Yale University, trude.storelvmo@yale.edu

Field experiments on Solar Geoengineering: Report of a workshop exploring a representative research portfolio

By Keith, David; Duren, Riley; MacMartin, Douglas

URL after Publication: http://rsta.royalsocietypublishing.org/lookup/doi/10.1098/rsta.2014.0175

We summarize a workshop that developed a portfolio of possible field experiments on Solar Radiation Management (SRM). The portfolio is intended to support analysis of potential field research related to SRM including discussions about the overall merit and risk of such research as well as mechanisms for governing such research and assessments of observational needs. The proposals were generated with contributions from leading researchers at the workshop. Possible gaps, biases, and cross-cutting considerations are discussed. Finally, suggestions for plausible next steps in the development of a systematic research program are presented. We hope that by that offering a description of potential initial field tests we will support a healthy debate about the wisdom of such tests while reducing spurious disagreements that arise from the divergent assumptions about the character of field experiments. Contact: Dr David Keith, Harvard University, david_keith@harvard.edu

NOTES 

Please note that both the media summaries and the journal issue itself represent the views of the authors and not the position of the Royal Society. 

The Royal Society is a self-governing Fellowship of many of the world’s most distinguished scientists drawn from all areas of science, engineering, and medicine. The Society’s fundamental purpose, reflected in its founding Charters of the 1660s, is to recognise, promote, and support excellence in science and to encourage the development and use of science for the benefit of humanity. 

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• Promoting science and its benefits
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