Though anthropogenic climate change has been widely recognized since the 1970s, geoengineering is a much more recent phenomenon. Considered to be entirely impractical by the scientific establishment, geoengineering was nothing more than a pipe dream for scientists of the 20th century since no one could secure research money to pursue it. Delving into the topic also presented a risk to scientists’ careers, since many considered the research immoral: offering the public hope of a quick-fix to climate change might discourage efforts to reduce greenhouse gas emissions.
For many, opposition to geoengineering stems from a sense that manipulating the environment on a large scale is simply wrong. It fundamentally changes the relationship between humanity and nature in a way that gives humanity far too much power. After all, technological development is what created the climate crisis in the first place, making some skeptical of technological solutions.
However, the taboo against climate manipulation was lessened in 2006 when Nobel Prize winning atmospheric chemist Paul Crutzen published a paper on the feasibility and perhaps necessity of exploring geoengineering options. Suddenly chemical manipulation of the atmosphere was not a fringe theory; it was in fact endorsed by one of climatology’s leading voices. Solar radiation management (SRM) was no longer some far-away theory.
Currently, research in geoengineering is still in its infancy, but there are some guidelines in place for the scientific community and for the general public to be at ease regarding the issue. These guidelines are called the Oxford Principles of Geoengineering. These sets of guidelines were implemented to guide the development of research and techniques into viable solutions without causing any harm, or reducing the probabilities of this. According to the Oxford Geoengineering Programme, “The Principles stipulate that any decision with respect to deployment only be taken with robust governance structures already in place in order to ensure social legitimacy”. The Oxford Principles are used in every technique of research.
Some scientists envision a complex system of mirrors in space whose orientation could be controlled from Earth’s surface. Turning the mirrors to face the sun would cause them to reflect a portion of sunlight back out into space and thus lessen the amount of radiation entering the atmosphere. Turning the mirrors parallel to the sun’s rays would cause them to have no effect at all. This would allow scientists to control almost instantly how much heat enters the Earth’s climate system. Drawbacks for this particular method include cost and technical difficulty: such a project lies outside the realm of current scientific capability and would require substantial and lengthy investment in research and development.
Others support the idea of surface whitening. This system seeks to increase surfaces’ reactivity, or albedo, and decrease the amount of heat being absorbed by Earth’s surface. It would entail whitening clouds to increase their albedo. This could be accomplished using sea salt mist near the ocean’s surface, which would then mix into marine clouds to make them whiter and longer lasting. Some members of the scientific community argue that sea salt could actually decrease cloud reactivity.
But by far the most commonly proposed mechanism for climate manipulation is sulfate aerosol dispersal. This involves spraying microscopic droplets of sulfuric acid into the stratosphere, where they then scatter radiation from the sun back into space. This mimics a phenomenon observed following the eruption of large volcanoes, which also release sulfates into the atmosphere. In the months following such a volcano eruption, temperatures are considerably and consistently cooler than average. This is because sulfuric acid reflected a portion of sunlight out of the atmosphere. In other words, injecting sulfates into the stratosphere would increase the Earth’s albedo, thus counteracting climate change by decreasing the amount of solar radiation reaching Earth’s surface.
Though opponents of SRM often cite uncertainty as a reason to avoid geoengineering, there is more of a historical precedent for sulfate aerosols than there is for rapid warming, meaning climate manipulation could be considered “the devil we know.” Volcanic eruptions give scientists an analogue to study the impact of sulfate injection, whereas the rate of anthropogenic climate change is unprecedented.
David Keith, professor of Applied Physics for Harvard University’s Paulson School of Engineering and Applied Sciences (SEAS) and Professor of Public Policy for the Harvard Kennedy School at Harvard University, is one of the leading voices in geoengineering, specially SRM and sulfate aerosol dispersal. In his paper, “Photophoretic levitation of engineered aerosols for geoengineering” published in 2009, he wrote: “Aerosols could be injected into the upper atmosphere to engineer the climate by scattering incident sunlight so as to produce a cooling tendency that may mitigate the risks posed by the accumulation of greenhouse gases. I examine the possibility that engineered nanoparticles could exploit photophoretic forces, enabling more control over particle distribution and lifetime than is possible with sulfates, perhaps allowing climate engineering to be accomplished with fewer side effects. The use of electrostatic or magnetic materials enables a class of photophoretic forces not found in nature […] Photophoretic levitation could loft particles above the stratosphere, reducing their capacity to interfere with ozone chemistry; and, by increasing particle lifetimes, it would reduce the need for continual replenishment of the aerosol. Moreover, particles might be engineered to drift poleward enabling albedo modification to be tailored to counter polar warming while minimizing the impact on equatorial climates. The use of particles engineered to exploit photophoretic forces may enable more selective geoengineering with fewer adverse effects than would the use of sulfate aerosol.”
From an economic perspective, geoengineering is incredibly inexpensive. Keith estimates that a yearly SRM project could cost around 700 million USD. According to the International Energy Agency (IEA), currently, the world spends 250 billion USD on clean energy annually, meaning that Keith’s prediction would be just over one quarter of one percent of current spending on clean energy alone.
When taking into consideration the future use of geoengineering, its implementation should be fully regulated to avoid intended and unintended misuse and effects. Additionally, the creation of agencies that promote private efforts should be encouraged in the international and scientific communities. Despite its evident flaws, sulfate aerosol dispersal should be given thorough attention, particularly in the fields of photophoretic forces, as they could make the sulfate particles sustainable and avoid interference with the ozone layer, and possible alternative particles that are healthier to the ecosystem. Moreover, countermeasures are to be created in the case of sudden interruptions and of excessive dispersal, in order to keep the right balance within Earth’s temperatures, always keeping in mind the Oxford Principles.
Goodell, Jeff (2010). How to Cool the Planet: Geoengineering and the Audacious Quest to Fix Earth’s Climate. Boston: Houghton Mifflin Harcourt.
Keith, David (2013). A Case for Climate Engineering. Cambridge, MA: MIT.
Robock, Alan. (2008). 20 Reasons Why Geoengineering May Be a Bad Idea. Bulletin of the Atomic Scientists. https://journals.sagepub.com/doi/full/10.2968/064002006
IEA (2020), World Energy Investment 2020, IEA, Paris https://www.iea.org/reports/world-energy-investment-2020