Reflecting Sunlight Recommendations for Solar Geoengineering Research and Research Governance (2021) / Chapter Skim
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6 An Integrated Agenda for Solar Geoengineering Research
6 An Integrated Agenda for Solar Geoengineering Research
Pages 191-258
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From page 191... ...
The agenda is also intended to address topics that are not already priorities for the broader climate change research enterprise; although at the same time, we acknowledge (and indeed hope) that some research can advance knowledge both for questions specific to SG and for climate change understanding more generally.
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. This includes chemistry and microphysics research to understand the properties of injected reflective particles and interactions with clouds and other atmospheric processes, engineering studies of the technical require ments associated with different SG technologies, and advancing strategies to monitor and attribute the climate impacts of SG activities. Research related to human health, social systems, and ecology aims to develop systematic ap proaches to studying impacts, to better characterize the range of possible im pacts, and to consider the uncertainties and limits to understanding impacts. • Social Dimensions.
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the social dimensions. Under these broad categories, the following are recommended as key research clusters to pursue: INTEGRATED RESEARCH AND GOVERNANCE FRAMEWORK CONTEXT AND GOALS FOR SG RESEARCH • Program Development Pathways • Future Conditions • Integrated Decision Analysis • Capacity Building IMPACTS AND TECHNICAL SOCIAL DIMENSIONS DIMENSIONS • Atmospheric Processes • Public Perceptions and Engagement • Climate Response • Political and Economic Dynamics • Other Impacts • Governance • Monitoring and Attribution • Ethics • Technology Development and Assessment Figure 6.1 Three broad categories and 13 research clusters included in the Committee's proposed re The research clusters included in the Committee's proposed research agenda.
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• Climate Response. Assessing how different SG approaches would affect key climate outcomes.
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Program Development Pathways: Designing an SG research program to maximize the prospects for broadly beneficial outcomes. The exploration and possible implementation of SG -- like any other technology -- is inherently a sociotechnical enterprise.
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For instance, the design of the research program will shape the nature of the scientific explorations undertaken, the knowledge from the scientific explorations will inform decisions about whether and how to proceed with further development and any possible SG deployment, and possible scenarios of SG deployment will inform relevant scientific explorations. The pathways taken in each of these dimensions will depend on the stakeholders involved in the discussions, their questions of interest, and the disciplinary perspectives brought to bear.
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Some critical questions to address in this research cluster include the following: • How and by whom are the scientific questions that need to be answered in an SG research program identified? • How and by whom are the primary objectives of SG determined (i.e., what risks are to be mitigated and by how much)
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? • How do we assess the sensitivity of the answers to these questions across dif ferent climate models or to uncertain physical parameters in models?
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that characterize a broad range of possible societal trajectories over the course of this century. Five SSPs have been developed as inputs into climate models in the lead up to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (Hausfather, 2018; O'Neill et al., 2017, 2019)
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or a fixed rate of change of temperature (MacMartin et al., 2014a) or cut the rate of change of net radiative forcing in half (Irvine et al., 2019)
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Some critical steps forward to advance this research cluster include the following: • Develop an improved set of SG scenarios for use in impacts modeling and policy assessments. These scenarios should characterize a representative range of socioeconomic, geopolitical, and climatic and other environmental conditions under which SG deployment decisions might be made.
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(See related discussion in Research Cluster 3, "Integrated Decision Analysis.")
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This will aid future decision making about setting further research priorities and weighing pros and cons of SG implementation. Some critical steps forward to advance this research cluster include the following: • Develop methodologies to incorporate socioeconomic model uncertainty into SG outcome uncertainty assessments, including both empirical uncertainty from climate effect and impact studies, as well as parametric and model-form uncertainties.
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Some critical questions to address in this research cluster include the following: • What kinds of capacities are needed in order to engage meaningfully with critical dimensions of SG research and research governance? • What are the current differences and commonalities in capacities between the Global North and South?
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Atmospheric Processes: Understanding chemical and physical mechanisms that determine how addition of materials to the atmosphere alters the reflection and transmission of atmospheric radiation. There is a wide array of research questions to explore in order to better understand the technical feasibility of SG interventions, and the exact nature of these questions 205
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Stratospheric Aerosol Injection It is clear from the Chapter 2 discussion that adding aerosols to the stratosphere would result in global cooling at the surface. Predicting the magnitude of this cooling, the climate response more generally, and the resulting impacts requires use of a climate model (discussed in Research Cluster 6)
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. Observations of the resulting size distributions could provide constraints that improve representation by climate models, but these observations would not be able to distinguish among the driving processes (e.g., vapor oxidation, heteromolecular and ion-induced nucleation, plume dynamics, or near-field coagulation of particles smaller than 10 nm diameter)
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As changes to cirrus would affect the overall radiative forcing, these processes will also need to be understood and properly represented in climate models. Some open research questions associated with the aerosol microphysics of SAI include the following: • For gaseous additions, what is the rate of formation and growth of particles from their precursors, and how does this depend on the time and location (latitude and altitude)
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How does stratospheric water vapor change as a result of the circulation changes and tropopause heating? • How does stratospheric ozone change due to changes in heterogeneous chemistry and stratospheric circulation?
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Labora tory experiments and detailed simulations provide a starting point for these questions. • Climate models are the critical tool to assess large-scale climate responses associated with SAI.
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Marine Cloud Brightening For understanding MCB, the highest priority research questions are how aerosols interact with clouds locally (and immediately) and regionally (and over days)
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Particle size could impact such feedback processes but we do not yet have the observations and models needed to determine the design criteria for a particle production and delivery system. Uncertain cloud processes. As discussed in Chapter 2, given the complex interaction between microphysics and turbulence in the marine boundary layer, at scales too small to be captured in global-scale models, idealized climate model simulations of MCB interventions do not provide reliable projections of climate impacts.
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modeling is an important tool for providing realistic turbulence, but it needs to be constrained by comparison to relevant observation and often lacks particles with realistic size distributions and chemical composition. Therefore, field 213
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Because the variability of turbulence in the Marine Boundary Layer (MBL) has few observations to constrain a very complex problem, observations need to target a series of measurements in three specific target regions (northeastern Pacific, southeastern Pacific, and southeastern Atlantic)
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. In short, it is not known whether radiative forcing is more buffered to the effects of added aerosols than is included in current climate models. Climate model development.
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Testing whether the process-based knowledge that we have obtained from these earlier studies is sufficient when incorporated in global models requires a sufficiently long and accurate measurement record to provide statistical overlap. The detailed characterization of the full annual cycle of clouds and their properties is the first and most basic objective that will fulfill this need for global climate models, some of which can be verified with existing satellite records, but providing accurate measurements of cloud vertical extent and more detailed radiative properties, in addition to characterizing the range and frequency of regional precipitation that occurs, would require in situ measurements.
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• Are the simplified model representations of photochemical oxidation, cloud processing, and other physical-chemical interactions sufficiently well represented to predict CCN? • How well do climate models predict aerosol properties relevant to CCN activation (aerosol amount, size distribution, composition, and hygroscop icity)
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If the cloud and aerosol simulations of models are realistic when considered separately, then it makes sense to assess the processes by which they interact. Here the evaluation includes the interaction of two complicated aspects that cannot be explicitly calculated in climate models: the microphys ics and the turbulence.
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If climate models can be developed that represent MCB accurately, then they provide important tools to assess the impacts of MCB on regional climate and ecosystems. Climate models could then also be used to design experiments to test whether those impacts are well represented.
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• Pursue, for the near term, modeling studies at the scale of LES, parcel and column models, and nested regional models -- all of which can help inform the improvement of climate model parameterizations. Pursuit of global-scale MCB modeling will be more useful after climate models are further developed on several key fronts: to better represent Earth's current cloud cover, to better quantify the uncertainties and feedbacks associated with perturbing cloud processes, and to provide a more accurate estimate of how changes in aerosol will alter climate.
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Some critical steps forward to advance this research cluster (for CCT) include the following: • Expand observations to better constrain how often cirrus forms and the cur rent distribution of homogeneous versus heterogeneous cirrus formation.
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In general, studies to date indicate that SG interventions would decrease globally averaged temperature and precipitation, but regional effects are less clear, and such interventions may alter the ocean and atmospheric circulation in unique ways. Climate models are the critical tool to assess large-scale climate responses associated with SG intervention strategies.
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For SAI, validation of climate responses with observations after volcanic eruptions provides some basis for confidence in using global climate models to assess the response to deliberate injection but with uncertainties, as described earlier. Evaluating effects of subgrid-scale mixing (e.g., at the scale of the "plume" released behind an aircraft)
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. Some critical steps forward to advance this research cluster include the following: • Use climate models to establish better estimates of the uncertainties in regional climate responses to SG interventions and assess how much those uncertainties can be reduced through research.
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° Incorporation of realistic causal links between cloud drop number concen trations and aerosol particle size distributions, which show the sensitivity and limitations of number enhancement. • Improve representation of SAI in global climate models.
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CPTs provide effective mechanisms to facilitate close collaboration and enduring links between process experts and model developers, thereby accelerating scientific understanding of key physical processes and leading to improvements in their representation in climate models.
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The needed research approaches range from detailed mechanistic studies of impacts on specific ecosystems or sectors to broader integrated studies of how different types of impacts and risks may be distributed across populations and geographic regions. Some critical steps forward for this research cluster include the following: • Explore the effects of SG interventions on a broader range of climatic and biogeochemical variables that are relevant to social-ecological systems, includ ing studies carried out at high enough resolution to inform understanding at regional and local scales and including a fuller range of SG deployment sce narios.
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5 This refers to bounded, partially enclosed outdoor experiments that are used in environmental science to bridge the gap between laboratory studies and the real world.
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This includes, for instance, the suite of in situ and remote sensing capabilities proposed herein for study of SAI (e.g., rapid response to volcanic emissions) and MCB (e.g., in situ sampling of cloud aerosol interactions and their radiative forcing impacts)
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Some critical steps forward to advance this research cluster include the following: • Determine what variables would provide the earliest and highest signal-to noise signals that could assist in attribution. • Explore approaches to improve the signal-to-noise in such observables to re duce the time needed for attribution (such attribution studies should explicitly consider the importance of natural climate and geophysical variability)
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For MCB, the primary question is the capability to produce salt particles of an appropriate size distribution that can be lofted into, and serve as nuclei for, boundary layer clouds. MCB deployment would also require the development of appropriate ships (or other delivery approaches)
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• Some development of specific capabilities may be necessary simply to enable scientific experiments. For instance, for MCB studies, there will be a need for spray nozzles that can produce a particular range of aerosol size distributions.
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Some critical steps forward to advance this research cluster include the following: • Conduct design and costs estimates for aircraft to deliver payload at altitudes up to 25 km (SAI)
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The substantive rationale -- that public engagement can improve the content of geoengineering research itself -- is underappreciated." (According to the normative rationale, broad publics should have opportunities for input on SG research, since these technologies have global reach and may affect people around the world; the instrumental rationale holds that public engage ment with SG research may reduce conflict and controversy.)
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Some critical questions to address in this research cluster include the following: • What constitutes effective practices for "meaningful public engagement" in SG research and research governance? • What does public engagement lead to in practice for SG research?
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For example, IAMs, an important tool for SG research discussed earlier in this chapter (see "Integrated Decision Analysis" cluster) , will need substantial input from political science and economics -- both at the macro level (e.g., regarding scenario design)
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Together with the ethics research related to such concerns (described later in this chapter) , economics and political science research can help with finding empirical evidence of the development of these dynamics, tracking the steps that lead to these phenomena, and assessing their actual success or failure at "mitigation deterrence" or technological or economic lock-in.
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• Are different systems of government relatively more or less compatible with broadly considered principles for SG governance (e.g., transparency, account ability, public engagement, etc.)
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. Relatively little research has examined the adequacy of existing resources for building capacity for SG research in developing countries or mechanisms for expanding that capacity.
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• Study the possibility and ethical permissibility of various approaches to ad dress harm and compensation issues, including harms that may arise with SG field tests with transboundary effects or as a result of deployment. • Assess the adequacy of existing resources for capacity building for SG research in developing countries and advisability of opening some exist ing pools of climate finance to SG research or establishing new sources of funding.
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Although fundamental questions regarding the moral permissibility of geoengineering remain important, the increased attention to specific geoengineering approaches is welcome because "geoengineering" is not a single, fixed technology; rather, it is an evolving array of ideas that includes not only possible SG technologies themselves, but also various approaches to researching, developing, governing, and making decisions about these technologies and how they might fit (or not fit) into a broader climate response (Stilgoe, 2015)
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Additional social science research to identify the values, perspectives, and concerns of diverse publics and stakeholders globally should inform ongoing priorities for ethics research. Some critical questions to address in this research cluster include the following: Justice and equity issues • How can SG research take account of the full range of ethical perspectives on this issue?
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How might ethics guidelines and permitting requirements for outdoor experiments take into account concerns that go beyond just physical effects? What role, if any, should the concept of informed consent play in governing SG field experiments?
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• What ethical considerations should inform research and research governance 9 Note that the recommended research on these questions reflects the need to better understand and anticipate ethical issues associated with deployment in order to inform SG decision making. This does not presuppose that SG should or will be deployed.
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This stems in part from arguments that outdoor experimentation at a scale large enough to affect regional to global climate is tantamount to actual deployment, and outdoor experiments short of that are legitimizing a road to deployment. For some, these objections are absolute, based, for instance, on fundamental objections to the idea that a small group of people has the right to "tamper with nature" in the absence of broad public input and consent and concerns about unintended consequences, intentionality of researchers toward outdoor experiments of increasing scale and impact, and lack of controllability and reversibility of outcomes.10 At the same time, some scientists involved in SG research argue that some form of outdoor experimentation is essential for advancing understanding of certain core physical processes, and that gaining such understanding will be essential if we are to credibly inform societal decisions about operational pursuit of SG.
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General Considerations for Setting Thresholds for Outdoor SG Experimentation The committee believes that thresholds for outdoor experimentation should address both the impacts of the potential perturbation on the climate and the impacts of the test materials on the environment. These dual concerns about outdoor experimentation motivate the dual threshold requirements -- based on the expected global mean surface temperature change and the mass of materials injected into the atmosphere -- that are described below.
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The potential for multiple independent experiments to have a larger aggregate effect on global temperature also makes it challenging to set firm thresholds for outdoor experimentation by individual countries. Thus, the committee suggests a threshold for individual experiments as well as for the aggregated effects of all outdoor experiments conducted globally in a given year.
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Recommendation 6.2: Deliberate outdoor experiments that involve releasing substances into the atmosphere should be considered only when they can provide critical observations not already available and not likely to become available through laboratory studies, modeling, and experiments of opportunity (e.g., observing volcanic eruptions, rocket plumes, or ship tracks)
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for a 100-yr time horizon (or 10 µK normalized to a 1-yr time horizon) ; and • for the sum/aggregate of all experiments conducted globally each year, any induced change in global mean surface temperature should be less than 1 µK (1 x 10-6 C)
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That said, even materials that might be considered safe in a general sense may be harmful in specific conditions, such as at high concentrations or if sensitive organisms are exposed. Before proceeding, proposed outdoor experiments would need to do a complete accounting of the environmental effects of an outdoor experiment that would consider how long and at what levels sensitive ecosystems might be exposed to a substance and the toxicity of the specific substance to organisms that would be exposed.
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• Research funding should be accompanied by support for implementing research governance and public engagement. Achieving the integrated strategy of research, research governance, and engagement requires dedi cated funding for advancing these other (non-research)
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As illustrated in Figure 4.1, these allocations should evolve as knowledge improves and the research needs adjust accordingly, thus the importance of ensuring flexibility for a large fraction of the funding. Field campaigns to obtain in situ measurements are likely to be the most expensive element of the SG research agenda.
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Targeted efforts to build capacity and new funding mechanisms for the "Social Dimensions" and "Context and Goals" categories will likely be required because Oversight, Management, Governance, and Public Engagement Context and Goals [~20%] program development pathways; future conditions; integrated uncertainty analysis; capacity building Social Dimensions [~20%]
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While the committee expects that the proposed research would be federally supported, it is also possible that support from philanthropic sources could help enable some of the proposed activities that are particularly challenging for government agencies to advance. Any philanthropic support for an SG research program would need to be pursued in a way that embodies the principles for the conduct and governance of research discussed in Chapter 5 and that ensures that the federally and privately funded activities are well coordinated.
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In addition, some field campaigns incorporate human dimensions research, engaging local communities and incorporating research on the implications for local policy and decision making (e.g., in the Large-Scale Biosphere–Atmosphere Experiment in Amazonia; [Avissar and Nobre, 2002]
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is just as important as understanding the technical question of "will it work." The SG research program proposed herein is, by design, quite different from most traditional environmental research and development programs -- with an array of interlinked research "clusters"; stepwise, iterative planning; and a strong governance framework that helps ensure transparency, accountability, human and environmental safety, and robust public engagement. Rather than being a burden on the research community, we suggest this governance framework will enable this research to proceed effectively.
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An Integrated Agenda for Solar Geoengineering Research Given that climate change is one of the most complex challenges that humanity has ever faced -- and that SG is one of the most controversial aspects of the response to climate change -- the scientific community must rise to this challenge with humility and creativity and stretch itself in new ways, across disciplines and national boundaries and beyond business-as-usual approaches to research.
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