Managing Solar Radiation
by Sonya Gurwitt '16
Global temperature increases in the coming decades will endanger coasts, small island nations, and agricultural yields, threatening the lives and livelihoods of people around the world. As a potential solution, some scientists have turned to geoengineering--using technology to engineer Earth’s climate. Geoengineering techniques aim to either reduce atmospheric CO2 concentration or incoming solar radiation. Many of these techniques are highly contested, and there has been little research into their feasibility or potential harms and benefits.
In a 2008 research paper (1), Alan Robock and colleagues attempt to shed light on the consequences of one form of geo-engineering, injecting aerosols into the stratosphere to cool the planet. Although the injections could substantially decrease temperatures over most of the globe, they might also disrupt rain patterns in certain areas and thereby affect food supplies for billions of people. Overall, their results and consequent analysis provide a number of significant worries about this type of geoengineering and suggest extreme caution when attempting an endeavor such as interfering with global climate.
The United Nations Framework Convention on Climate Change (UNFCCC) states that its “ultimate objective…is to achieve…stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system” (2). Scientists generally agree that this level would be a maximum of 450ppm of atmospheric CO2 and would be necessary in preventing dramatic temperature and sea level rise, reduced agricultural yields, and other catastrophic climatic consequences. Yet, the UNFCCC has taken little action to prevent rapidly rising CO2 emissions, and work towards mitigating or fixing problems caused by climate change is at a virtual standstill. Given the sluggishness of current methods and negotiations, the idea of “fixing” the climate with technology seems tantalizing, giving rise to a whole slew of proposed geoengineering methods by scientists.
Countries that have signed onto the UNFCCC. Green = industrialized + required to support other countries. Blue = economies in transition. Orange = developing. [image via]
One kind, called “solar radiation management” (SRM), involves either stratospheric aerosols or sun-shields in space to reduce incoming solar radiation and thus cool the planet. This idea arose from observations that volcanic eruptions, which similarly disrupt solar radiation with billowing clouds of ash, have temporarily cooled the planet. However, Robock et al. point out that, rather than having a consistent cooling effect over the entirety of the planet, tropical eruptions have produced changes in atmospheric circulation that actually led to warming over continents in the Northern Hemisphere (1). This warming persisted for only a few years, but the effect could be generalizable to continuous aerosol clouds. Furthermore, eruptions have also caused decreases in precipitation accompanying the Asian and African monsoons, as well as large stratospheric ozone depletion (1). From these observations, they conclude that, while evidence from volcanic eruptions might indicate that similar geoengineering techniques could produce a cooling effect in certain parts of the world, it does not prove the safety or overall effectiveness of these techniques.
Using computer simulations, Robock et al. conducted experiments for both tropical and Arctic SO2 injections into the stratosphere. They were interested in the response of the climate system to a “permanent” stratospheric aerosol cloud, in contrast to the transient nature of the effects of volcanic eruptions. They ran their experiments by virtually injecting SO2 at a constant rate for 20 years (of varying amounts and in both the Arctic and tropics), then continued the simulations for an additional 20 years to examine the aftereffects. They compared these simulations to a run simulating the IPCC business-as-usual scenario, which assumes continuous, high CO2 emissions and accompanying increases in temperature.
From their simulations, they found that the more SO2 was injected, the more global warming was reduced, though injection at the Arctic had a smaller effect than at the tropics. However, they also found that, as temperature was reduced, global precipitation declined on average due to weakening of the African and Asian summer monsoons, a finding consistent with the observed effects of volcanic eruptions. Finally, they found that although SO2 injections could counter rapidly melting Arctic sea ice and even cause increased sea ice production, the ice would melt quickly soon after the injections stopped.
Injecting 5 megatons of SO2 into the stratosphere at the tropics would reduce surface air temperature (SAT) around the world. [image via]
These results demonstrate that injecting aerosols into the stratosphere would cool the planet and could even reverse global warming. However, they also suggest that this reversal might come with potentially catastrophic consequences. For one, the disruption of African and Asian summer monsoons predicted by their simulations would seriously jeopardize the food and water supplies of billions of people. Moreover, the public might see SO2 injection as a temporary fix to stall for time if strategies to reduce CO2 emissions or mitigate other climate change effects are not implemented quickly enough. Yet, it cannot be used as a temporary fix. Robock et al.’s results demonstrate that if injection were to stop due to some sort of technical problem, political issue, or the discovery of unforeseen negative consequences, the planet would begin to warm at an even faster rate than projected in a business-as-usual scenario.
Compared to real-world experiments, simulations have limitations: they rely on certain assumptions that may or may not be correct. Furthermore, Robock et al. state that there is no known practical mechanism for injecting SO2 into the stratosphere on a continuous or episodic basis at the rates used in their simulation. Thus, there is no guarantee that SO2 injection is even feasible or that the simulations are indicative of the safety and effectiveness of potential mechanisms for SO2 injection.
However, assuming their results are accurate, do these likely negative repercussions outweigh the possible positive effects of global temperature reduction? Robock et al. simply state that their results do not support that using sulfate aerosol injections to prevent sea ice from melting and temperatures from rising will be safe and effective or will avoid negative effects on the rest of the biosphere. They conclude that the costs, benefits, and dangers of different options must be weighed before deciding whether we should use this type of geoengineering in an attempt to counter the worst effects of global climate change.
Their conclusion lacks mention of one additional danger of tinkering with the climate system. SRM techniques target the symptoms of climate change – warming temperatures – rather than the problem itself. The problem in this case is the rise in atmospheric CO2, which is really a symptom of the underlying mindset and societal values that led to high emissions in the first place. SRM could produce the undesired effect of inhibiting solutions to both. Not only would it do nothing to stop rising CO2 emissions, it might encourage more emissions in that it would cause a sense of complacency, as people would believe that at least some climate change issues were being addressed. Furthermore, the mindset of human power over the Earth that caused emissions in the first place could actually be reinforced through this attempt to exert technological dominance over the climate system.
These additional consequences, combined with the dangers presented by Robock et al. would jeopardize food supplies and establish reliance on continuous SRM techniques. In this case, it seems that the potential costs outweigh possible benefits. What seems like a “golden” idea to some might turn out to be nothing more than fool’s gold, dangerous fool’s gold at that – tempting society down a path paved with hazards from which we might have more difficulty recovering than avoiding.
The author is a guest contributor. If you would like to publish a piece on Ursa Sapiens, please contact us!
Leave a Reply.