There is some reason to believe that the summerless year that followed the eruption of Mt. Tambora in 1816 inspired the horror novels Frankenstein and The Vampyre. Some have also argued that Edvard Munch’s famous 1893 painting ‘The Scream’ was also inspired, in part, by the sight of a sky after a volcanic eruption.
A sufficiently powerful volcanic eruption can spew sulphates and other aerosols into the stratosphere, cooling the air there. This fact has motivated human efforts to artificially spray aerosols into the stratosphere to slow global-warming, with occasional support from the U.S. government, among others. The U.S. government is currently officially supporting research on solar radiation management (SRM).
In a controversy late last year, a private venture called Make Sunsets released tiny amounts of sulphur dioxide into the stratosphere using balloons in an effort to sell ‘solar-dimming’ as a way to offset carbon emissions. To many researchers the event was a major red flag signalling the colonisation of common goods like the atmosphere by private players.
The latest media buzz on this front comes from a paper recently published in the journal PLoS Climate on February 8. Researchers from the U.S. have proposed that billions of tonnes of dust can be launched from the moon to a Lagrange point – a point in space where the earth’s and the Sun’s gravitational fields cancel each other out. The feat is obviously beset by severe technical and economic challenges, yet there is interest in it.
The science of the consequences of volcanic eruptions is well-established. Aerosols in the stratosphere, especially radiation-scattering ones such as sulphates, do have a cooling effect. This is what led to the ‘year without summer’ – but it would be unwise to forget the other consequences of the same eruption. The cool summer led to widespread drought across the planet, sent crop yields plummeting, leading to disease and starvation. Many climate models have confirmed that dimming the amount of incoming sunlight with stratospheric aerosols will have similar outcomes.
Some recent studies have argued that the resulting drought won’t be as harmful and that the GDPs of most countries will be positively affected by this approach to SRM. But we should remember that even state-of-the-art climate models are skilled only at guessing the temperature response to changes in solar radiation caused by changes in the concentrations of greenhouse gases and stratospheric aerosols. In addition, these temperature projections are best at the continental scale – not at the regional scale, which matters when it comes to heatwaves, drought, and such.
The fact remains that climate models are still woefully inadequate at estimating the precipitation response to solar radiation perturbations at all scales. In other words, any projections related to changes in rainfall, as a result of throwing up dust into the atmosphere or in space to block sunlight, will be highly uncertain.
In turn, concluding that SRM won’t have unintended consequences in the form of drought and crop losses or that it will lead to ‘positive’ changes in the national GDPs, based on models that can’t reliably predict precipitation, would be foolhardy.
We need to bear in mind the fortunes of the Global South, which may once again be an innocent bystander to large-scale experiments by the Global North – just like the Global North proceeded to industrialise and triggered global warming, the consequences of which will bear most heavily on the Global South.
Other climate mitigation strategies, such as the use of renewable energy, emissions reductions schemes, carbon-capture technologies, and bioenergy, are not expected to have any dangerous unintended consequences. On the the hand, spraying aerosols even in a small pocket of the stratosphere will have global consequences that we can’t fully quantify at present.
Many natural as well as social scientists have expressed grave concerns about the science and governance issues of SRM. Who will decide when and where to deploy aerosols, and how much? Who will monitor for unintended consequences? If one country conducts an experiment that affects rainfall in another country, who will bear liability? Will there be compensation for the damages caused? Note that we are still struggling with the concept of ‘loss and damage’ under the U.N. Framework Convention on Climate Change, an instrument to compensate countries for the harm caused by climate change. Compensation for the accidental outcomes of SRM will be even more contentious.
The University of Oxford and the Asilomar Conference have proposed guiding principles for attempts to geoengineer the climate. Some points: Those involved must clearly and explicitly report the science and technology of these approaches along with their consequences – the good, the bad, and the ugly; the governance of the deployment and monitoring, verification, and reporting should be democratic and inclusive; and stakeholders must be codify and preemptively agree on compensation mechanisms for any harm.
Finally, a major caveat of the aerosol-loading approach is that there will be a rebound effect once spraying stops and the aerosols are washed out of the atmosphere. That is, when the temporary cooling effect is on, we must still reduce emissions. If we don’t, the cooling effect will end and a heating period will begin.
But if industrial and political leaders are thinking of the cooling as a licence to continue with business as usual, then we will definitely be creating a Frankenstein’s monster.
Raghu Murtugudde is a visiting professor at IIT Bombay and an emeritus professor at the University of Maryland.