David Keith is a professor in Harvard's Schools of Engineering and of Public Policy, and founder at Carbon Engineering.
Edward Parson is professor and co-director of the Emmett Institute on Climate Change and the Environment at UCLA, and senior research associate at the Centre for Global Studies, University of Victoria.
People's initial reactions when they learn about the prospect of solar geoengineering typically involve some mix of horror and relief: horror at the prospect of a dangerous and uncontrolled technical fix, and relief that new technologies may offer the prospect of additional reductions in this century's severe climate risks.
But wherever your views fall on this spectrum, the case for serious research on solar geoengineering, and serious examination of its governance challenges, is compelling. Indeed, it is becoming increasingly likely that some form of climate engineering will be necessary to achieve the Paris target of limiting planetary heating to well below 2 C.
Solar geoengineering – one type of climate engineering – would involve reflecting a small amount of incoming sunlight back to space. The most plausible method is to use aircraft to make a fine mist of reflective material in the stratosphere, where it would act like a thin cloud reflecting a little sunlight back to space. Neither science fiction nor saviour, the goal of such intentional climate intervention would be to offset some of the climate changes caused by elevated greenhouse gases.
Most climate models agree that carefully managed solar geoengineering can reduce projected changes in both temperature and precipitation over nearly all the Earth's land surface. It can slow and likely reverse sea level rise, and provide some reduction to rapidly mounting threats to coral reefs, by slowing both rising temperatures and ocean acidification. It appears particularly effective at slowing current and projected increases in the strength of tropical hurricanes.
How should the world consider climate engineering? As a taboo, pushed aside from the centre of climate policy? Or, as a risky solution embraced all too quickly by opponents of emissions cuts? Between these polar extremes lies a wide range of opportunities for responsible exploration – and a great opportunity for Canada to exercise effective international leadership.
Solar geoengineering should be considered along with another form of climate engineering – removing previously emitted carbon dioxide from the atmosphere, often called "negative emissions."
Geoengineering approaches are, at best, supplements to emissions cuts, not substitutes for them. Emission must still be cut. But early evidence suggests that a combination of emissions cuts, carbon removal and solar geoengineering could provide better protection against climate risks, perhaps substantially better, than emissions cuts alone. Such strategies could stop and even reverse the progression of climate change.
Solar geoengineering – our focus here – offers both the high-stakes prospects of large potential benefits and serious grounds for concern. The most basic concerns pertain to how well it could work and its environmental impacts and risks. Early research has shown surprisingly promising results, quite at odds with a few widely circulated, overconfident claims of harms: e.g., that it would destroy the South Asian monsoon or distribute large regional gains and losses. Yet there is plenty of uncertainty, and additional limits and risks, not presently identified, will surely be found.
The strongest grounds for concern pertain to how solar geoengineering would be used and governed. Ensuring that it is used (if used at all) in ways that bring global benefits, fairly distributed, with any attendant harms minimized and justly compensated, presents novel challenges to global governance. The politics will be hard and may be ugly. Forces opposing emissions cuts – mainly fossil-fuel interests – may exaggerate claims of solar geoengineering's effectiveness, or use the new uncertainties it introduces to argue for further delay in cutting emissions. The reasonable fear that solar geoengineering may be exploited to obstruct needed emissions cuts underlies much of the resistance bringing this topic out of the shadows.
Uncertainty about the effectiveness and risks of solar geoengineering should be addressed with a serious research program. Such research would include both modelling and small field experiments. Some have expressed concerns that doing this research would inevitably lead to the technology's deployment. But these claims are belied by abundant historical experience, and – if true to any degree – are easy to mitigate by careful design and management of research programs.
Longer-term questions about how to govern future proposals to use solar geoengineering need serious critical examination, and the sooner, the better. But this is not a reason against pursuing scientific and technical research, particularly when the risks of solar geoengineering are weighed against the increasingly severe and intractable risks of climate change itself. Yet on both the research and governance fronts, progress has stalled. The United States saw promising steps toward developing a federal research program in the past two years of the Obama administration, including recommendations to that effect from both a National Academy of Sciences committee and the U.S. Global Change Research Program.
But, as in so many areas, the Trump administration has changed the game, and not for the better. Considering its retreats from responsible climate-change policy, from international co-operation, and from science, many parties now fear that this administration's embrace of these technologies would do more harm than good.
A Trump tweet such as "Geoengineering is GREAT, no need to cut emissions" might be the worst case, but promotion of solar geoengineering research by agency officials or Congressional leaders who deny the severity of climate change, pursue expansion of fossil fuels, and demean scientific research when they don't like the results would not be much better.
Research is needed, but it must take place under conditions that make it more likely to help than hurt. The first condition is that expanded scientific and technical research must proceed in parallel, and be linked, with deliberation and development of international governance. A substantial research effort without governance would be reckless, yet effective governance cannot be developed without understanding the technologies that need to be governed – knowledge that can only be developed through research. Achieving linked progress in research and governance will be a delicate, iterative process, which will succeed or fail based on careful institutional design and trust in the leadership of both endeavours.
That need for trust is the second condition. The institutions leading these endeavours – whatever combination of governments, scientific bodies and other non-governmental organizations – must inspire and earn trust through a track record and commitment to international consultation and co-operation, to serious action on climate change that prioritizes strong emissions cuts and adaptation efforts, and to the constructive and impartial use of scientific knowledge and evidence in public policy.
Does this sound like Canada? We think so. While Canada's record on these matters is not perfect – indeed, Canada has at times exhibited an unfortunate gap between climate rhetoric and action – its quiet virtues and present commitments shine brighter in view of the chaos enveloping our southern neighbour. Canada has other advantages, too, that can help it play a leading role in developing responsible research and governance for climate engineering: its status as a middle power in international affairs; its exposure, as an Arctic nation, to some of the most rapid and extreme manifestations of global climate change; its strong record of effective science-based environmental assessment and advisory processes; and its strong base of scientific expertise in relevant areas such as climate modelling, stratospheric dynamics, remote sensing, ecological system studies and Arctic ecosystems, and the cryosphere.
A serious Canadian initiative to lead global efforts on climate engineering research and governance might include the following elements. First, federal funding for relevant investigator-driven academic work. Second, directed federal funding for applied research and development at agencies such as the Canadian Climate Centre, the Canadian Space Agency, and NRC. Third, establishment of a senior advisory committee on climate engineering governance, jointly convened by the Ministries of Environment and Climate Change, and Global Affairs, with substantial participation from scientific, environmental and other relevant civil-society groups. Finally, last but not least, a broad effort to foster public consultation and deliberation.
In pursuing such an initiative, Canada would not be acting entirely alone. Tiny tentative research efforts are developing in Europe, China and elsewhere. But a crucial leadership void exists, in developing a vigorous research agenda and in the linked development of governance. Canada is uniquely well positioned to provide that leadership. Canadian engagement could steer international debate on how, and whether, these technologies can be developed and used, prudently and justly, in addressing the grave threat that climate change poses to this divided planet.