In early July, in Germany's historic Berlin-Brandenburg Academy of Sciences and Humanities, academics and analysts from a wide range of disciplines gathered to participate in a research symposium on climate engineering. The fledgling field - only some of those present at the conference even consider climate engineering to be their primary research interest - has steadily been picking up momentum over the past decade. More commonly known as "geoengineering," it is generally taken to refer to "deliberate large-scale manipulation of the planetary environment to counteract anthropogenic climate change."
However, even most supporters of geoengineering are wary of deployment at this point in time, and the consensus among much of the research community seems to be that the repercussions of such direct, intentional intervention in the climate would be "irrational and irresponsible." Correspondingly, the majority of speakers at the Berlin conference were not engineers, and questions of ethics and governance figured more prominently in the various talks than breakthrough new technologies. But with current carbon emissions showing no signs of slowing down fast enough to make a significant dent in global warming over the coming decades, scientists are increasingly searching for alternative ways to cool the planet. And one possible avenue towards this goal - one which is slowly attaining a controversial following - is the injection of small reflective particles into the stratosphere; a risky but potentially highly effective way to counteract warming by reflecting sunlight back into space.
Too Little Too Late
With Pope Francis devoting an encyclical to environmental issues in June, and the United Nations Climate Change Conference (COP21) due to take place in Paris this coming December, it may seem like the tide on climate action is turning. Indeed, the ambitious stated goal of the conference, in which representatives from almost 200 countries will gather, is to reach a binding, universal agreement limiting greenhouse gas emissions in "all the nations of the world." But the idea that any agreed-upon curb in emissions can limit the global temperature increase to 2 °C above pre-industrial levels is being increasingly questioned.
That's because even if the conference is a runaway success - even in the unlikely scenario that the participating nations not only agree upon but actually manage to reach their target emissions cuts - warming is still expected to be an undeniable reality. Even if in a feat of unprecedented global coordination, emissions peaked by 2020, the carbon already emitted would remain in the atmosphere and continue to gather until we hit zero emissions, driving a rise in global temperature. Predictions vary, but if we were to stop the rise in carbon emissions today, freezing them at 10 billion tons per year, scientists expect that warming over the 21st century would still be somewhat above the 2 °C mark (though there are admittedly many uncertainties involved in this estimate). At this point, no matter how well the global community handles future emissions, the rise in temperatures is an almost inevitable reality and will have significant social and environmental consequences.
This growing realization is what has prompted some to begin looking into more active ways of dealing with global warming. "Carbon casts a long shadow into the future," writes David Keith, who holds a joint appointment at Harvard University as a professor of public policy and applied physics. "A thousand years after we stop pumping carbon into the air the warming will still be about half as large as it was on the day we stopped - assuming, of course, that we do nothing to engineer the climate."
Enter Geoengineering
In June 1991 Mount Pinatubo, an active volcano in the northern provinces of the Philippines, erupted, releasing about 17 megatons of sulfur into the atmosphere. The released particles formed a layer of sulfate aerosols that spread around the earth, reducing the amount of radiation hitting its surface and leading to an estimated decrease in global temperatures of about 0.5 degrees Celsius.
This monumental climate event has been one of the driving forces behind Solar Radiation Management (SRM), which, alongside Carbon Dioxide Removal (CDR), is one of the two umbrella categories of approaches for geoengineering the climate. SRM proposals generally seek to reflect a fraction of the sun's light back into space. This can be attempted in a variety of ways - from painting roofs white to launching reflective satellites - but the most commonly discussed method is the deliberate injection of aerosols into the atmosphere. Like the eruption of Mt. Pinatubo, particle injection would be expected to reduce the levels of radiation hitting the earth, thus creating a cooling effect and potentially lowering the earth's temperature back to pre-industrial levels. CDR researchers, on the other hand, propose developing technologies to directly remove CO2 from the air. Some, for example, suggest injecting minerals into marine ecosystems, which would increase the pull of carbon from the atmosphere into the oceans ("ocean fertilization"). Others advocate simply planting forests.
The risks involved with most CDR approaches are generally considered to be limited, in that they deal directly with the problem (carbon emissions) - and are not so different in effect from simply curbing fossil fuels. Thus, some methods of carbon sequestration have gathered tentative support from environmental groups and funding from government bodies. SRM approaches, on the other hand, deal in a sense only with the symptoms - the rise in global temperatures - and so are more likely to trigger undesired side effects. Still, the tradeoffs of the low risk associated with CDR methods are their high costs and the long expected timescale - likely decades - before they bring about meaningful change in the current climate trajectory. Injecting particles into the atmosphere, while more risky, is expected to trigger cooling almost immediately after deployment and to be cheaper and more technologically feasible.
According to Ken Caldeira, a climate scientist at the Carnegie Institution for Science's Department of Global Ecology, there is agreement among most climate scientists that sulfur-based SRM would be effective in lowering the earth's temperatures. "Broadly, the climate modeling results are consistent with volcanic observations," he explained in an interview with the HPR. "[The earth] would probably start cooling within a year after a solar geoengineering system were deployed."
Particles could theoretically be pumped into the air using a wide range of delivery systems, from modified jets and airships to guns and rockets. The SPICE Project, a collaborative investigation of the effectiveness of SRM that took place in Britain, looked at the possibility of disbursing particles from a pipe tethered to a large balloon. The different methods vary in cost and effectiveness, with the cheaper technologies likely requiring more development time. But as even the pricier options are estimated at a few billion dollars per year, costs are generally considered to be affordable across the board - especially when compared with the enormous economic consequences of cutting back on cheap fossil fuels. Caldeira quotes one of David Keith's catchphrases describing sulfate SRM technologies: "fast, cheap, and imperfect."
"Delusional in the Extreme"
The idea of shading our planet with an enormous cloud of sulfur, while giving hope to some, has generally invoked feelings that range from mild discomfort to strong, vocal opposition. Former Vice-President and environmental activist Al Gore said of geoengineering that "the hubris involved in thinking we can come up with a second planet-wide experiment that would exactly counteract the first experiment is delusional in the extreme" and has referred to the idea of using sulfur dioxide to reflect sunlight as "insane" and "utterly mad."
One frequently sounded concern is that the availability of an easy technological fix for global warming will lead nations to shirk from their commitments to lower greenhouse gas emissions. Moreover, cooling the planet by reducing CO2 is not the same as cooling the planet by reducing sunlight; temperature rise is just one of the many implications of increased carbon concentration in the atmosphere. Oceans, for example, would continue to acidify as they absorb larger and larger amounts of carbon from the air, endangering many underwater ecosystems. Less sunlight would also affect the hydrological cycle, with expected changes in rainfall and evaporation, according to Caldeira.
Another idea that has many worried is the "termination shock." While the current trajectory of warming will influence the planet in ways we can't quite predict, the relatively gradual process ensures that ecosystems will be able to at least partially adapt. "An awful lot of the impact [of global warming] is linked to how fast temperatures rise," Edward Parson, co-director of the Emmett Center on Climate Change and the Environment at UCLA, told the HPR. "So even if you [just] slow down temperature rise, you can still avoid a lot of the consequences." If an SRM program were suddenly halted - which could happen for a host of technological and political reasons - and temperatures rapidly accelerated, however, the consequences could potentially be far more dangerous. The earth, rather than having decades to adapt to gradual change, would have just a few short years.
Then there are political considerations. Provided the technology exists, regulation and governance still pose a significant challenge. "It will be a big job to develop the kind of institutional capacity required to manage this sort of stuff," said Parson, adding that technical and operational capability that large-scale deployment would require is "substantially greater than anything that current international bodies have."
But even if potential deployment is overseen by an agreed upon international authority, that body would still, according to many, have unhealthy leverage over the climate, which could easily be misused. Add that to the fact that climate change will not affect all nations evenly - while some stand to suffer significant economic and environmental losses, others might actually benefit (through increased rainfall, for example) - and agreed upon, global governance begins to seem even more difficult. Keith has likened this potential mess to "frat boys arguing over the thermostat." The low estimated cost of SRM presents yet another complication: there's not much to stop a few small Pacific island states, which are particularly threatened by rising sea levels, to group together and jointly spend the several billion dollars required to develop and deploy some form of SRM - regardless of the consequences that might have for the rest of the world.
Indeed, Ken Caldeira points out that it while it may take over half a century to see benefits from changed climate policy, deploying sulfur aerosols is something that decision makers could do to affect weather in a "politically relevant timeframe" - so the pressure to do so, especially considering the low costs, could at some point become intense.
Finally, there are the "unknown unknowns" - consequences that are wholly unexpected by current research but are sure to surprise us once the technology is tested. Indeed, some scientists have doubted how technically feasible SRM really is. "David Keith gives the impression that the engineering technologies needed for delivery of particles to the stratosphere [are] 'straightforward,' 'cheap' and 'ready to go,'" writes Dr. Hugh Hunt, a senior lecturer in the Engineering Department at Cambridge University who led the investigation of delivery methods in the SPICE project. "No technology exists for delivery of [10 million] Tonnes per year of 'stuff' to 20 [kilometers]. If we try to do it we will find difficulties that were unforeseen." However, Hunt concludes - as do Keith, Caldeira and Parson - that this is a case for, not against, further research into SRM. "It may turn out to be impossible, [but] the sooner we find this out, the better."
A Bad Idea Whose Time has Come?
Indeed, Hunt is somewhat frustrated by the high ratio of social sciences publications to engineering ones in the field of geoengineering. If we're going to talk about this, he feels, we should at least have something tangible to talk about. Others, Keith among them, feel that the debate is healthy, in that "it suggests that we have learned something from past instances of over-eager technological optimism and subsequent failures." But both agree on the importance of public support for further research.
A few years ago, the SPICE project cancelled a small-scale experiment with a balloon due to perceived public discomfort, despite planned testing only of basic aerodynamics (no sun-blocking particles were involved). Keith, too, has been holding back from further research due to lack of government funding. He has maintained that "it's important in a democracy that these experiments go through a proper external risk assessment with substantial public funding."
But public opinion may slowly be warming to the idea of climate engineering. A 2011 poll that was conducted in the United States, Canada, and the United Kingdom showed that 72 percent of respondents either "support" or "somewhat support" the study of SRM. A few months ago, the Natural Resources Defense Council released a statement expressing tentative support for research, saying that while "there's absolutely no substitute for slashing fossil fuel emissions," it would be "prudent to do research into geoengineering."
SRM may not yet be, as journalist Eli Kintisch put it, "a bad idea whose time has come," as the international community is probably far from ready to make use of such drastic means to fight climate change. Nevertheless, it is becoming increasingly difficult to argue against research into technology that might be the only fast enough method to reverse global warming - especially considering the pressure future governments may face to act swiftly. The time to deploy SRM technology to cool the earth may never come, but if it does, that decision should be made with full knowledge of the risks and consequences.
Image source: Wikimedia // Arnold Paul // Hugh Hunt // The Peruvian Ministry of Affairs
