The window for avoiding disastrous changes in our climate remains open. Though it is too late to stop the warming that's locked in due to the greenhouse gases already in the atmosphere, concerted global action can still turn back the worst impacts.
But time is tight and the major emitters have been slow to act, so we at EDF are sometimes asked whether humankind could deploy some sort of technological solution that puts the genie back in the bottle.
Broadly speaking, this suite of technologies is known as geoengineering, defined by the National Research Council of the National Academy of Sciences as the "deliberate intervention in the climate system to counter climate change." Some people think the possibility of a technological 'fix' provides an excuse to justify emissions inaction. But usually the question is sincere: Do we have a backup parachute — is there a planetary-scale fix that can stop the warming if we fail to cut emissions in time?
The short answer is, no. It would be criminally negligent to count on geoengineering to save the day. The best science says unequivocally that there is no technology yet conceived that could quickly or easily 'fix' the impacts of human-caused changes in the atmosphere. The best we could hope for is masking some of the impacts. That means we still need to do everything we can to address the emissions problem head on. We need to cut climate pollution now.
That said, we also think it makes sense to explore and understand this issue. As the world warms, somebody is bound to propose use of geoengineering technologies, or even deploy one of them. We need to understand the potential consequences before that happens.
A number of geoengineering ideas have been suggested, though none have been put to a real test. They fall into two main categories.
First is carbon dioxide removal (CDR), which tackles the root cause of climate change by taking greenhouse gases out of the atmosphere. Some concepts, such as reforestation, have been around for a long time, have few global risks and can address a relatively small proportion of the problem. Other efforts to capture CO2 using man-made tools are much less well developed, and generally considered to be economically unfeasible with current technology.
The second, known as solar radiation management (SRM) or "albedo modification," involves reflecting a small amount of incoming radiation (energy) back to space — essentially opening a gossamer parasol over the earth to reflect a small part of the sun's rays. Unlike CDR, experts think this sort of approach might conceivably be within reach. The question is whether it's a good idea.
Recently, I served on a committee that issued a the National Research Council's first-ever report examining two such strategies: First, injecting natural or synthetic reflective particles into the stratosphere via planes, rockets or other means; and second, increasing the brightness of marine clouds, either by spraying seawater droplets into the atmosphere or modifying exhaust from cargo ships and other vessels.
The report found that SRM interventions are likely to be less expensive than greenhouse gas emissions reduction strategies, making it theoretically feasible for a nation, corporation or group of wealthy individuals to deploy them unilaterally. These methods might be able to mask some of the heat-trapping impacts of greenhouse gases relatively quickly.
However, these methods are unproven and highly uncertain, and their risks and side effects are largely unknown and potentially substantial. And remember that they would only provide a temporary mask; any positive result would simply offset some of the climate effects without addressing their actual cause. Nor would SRM technologies address the growing impacts of increasing ocean acidification caused by rising levels of atmospheric CO2.
Not a Magic Bullet
Without exception, all scientific reports have categorically stated that SRM is no substitute for reducing greenhouse gas emissions, and that the environmental, economic, social, ethical, political and legal risks of using these technologies are poorly understood.
Some CDR approaches could play a role mitigating emissions or increasing the speed at which we could draw down greenhouse gas concentrations in the atmosphere once new emissions are drastically reduced. But it will still be necessary to address uncertainties and costs, while building resilience in social and ecological systems to reduce the inescapable effects of climate change.
So far, however, SRM research has been limited. Proponents often point to major volcanic eruptions, which deliver reflective sulfur particles to the stratosphere, as the test of such ideas. These are imperfect analogues to deliberate geoengineering, but observations suggest large volcanic emissions have negatively affected rainfall and crop growth in several regions of the world.
What's more, scientists warn that since SRM would merely hide the effects of greenhouse gases, we'd be stuck doing it forever (unless it were deployed to address a climate emergency at the same time as serious reductions in greenhouse gas emissions were underway). If it was ever necessary to stop SRM efforts in a high-carbon dioxide world, the result would be rapid rebound warming that would likely be far more destructive ecologically and socially than if nothing had been done to begin with.
Governance and Small-Scale Research
To better understand the implications of this technology before there is a sense of urgency to use it to address a growing emergency, many scientists, including the authors of the NRC report, believe there are opportunities to conduct valuable small-scale outdoor SRM-related research with negligible physical risks. We argue that such research would not only give us information about larger scale research and deployment, it would help us better understand the climate system. You can read EDF's full position on geoengineering.
The NRC report and most scientists also believe that research needs to be conducted with strong governance to ensure it is conducted transparently, with civil society input and interests in mind. Otherwise, the fear is that SRM could be seriously considered or even deployed in the face of a climate emergency before the world has either international oversight structures in place or a reasonable understanding of the implications.
The only international agreement that mentions SRM research is a 2010 non-binding decision by the United Nations Convention on Biological Diversity (of which the U.S. is not a member) that "invites" members to ensure that any geoengineering tests "that may affect biodiversity" do not proceed. The decision provides an exception for "small-scale scientific research studies that would be conducted in a controlled setting."
We believe that any such research requires effective governance structures to deal with the profound social, ethical and geopolitical consequences. In 2010, EDF co-founded the Solar Radiation Management Governance Initiative with the Royal Society and The World Academy of Sciences, in order to engage a diverse and global range of voices to discuss SRM research and appropriate governance.