Geoengineering is often basically about putting stuff into the atmosphere or into space that will block some of the light emitted by the sun from reaching the surface of the Earth. Since humans seem to be incapable of reducing their use of fossil fuels, so some other way must be found to reduce the amount of energy the planet receives from the Sun every second of every day.
In theory, if we could find a way to reduce the power of sunlight by about 2%, we could go right on burning every lump of coal, barrel of oil, or cubic foot of methane we could wrest from the Earth in perpetuity, which would delight the executives of the fossil fuel companies and their shareholders. The concept is like a cosmic dimmer switch that would allow us to turn down the intensity of sunlight just a teeny bit. It sounds simple but it will cost trillions of dollars, has no guarantee of success, and could cause unimaginable harm to life on our little blue planet in a minor galaxy at the far edge of the universe.
There are two ways geoengineering could work — in theory. First, we could inject tiny particles of sulfur dioxide or water vapor or sea salt high into the atmosphere. Second, we could create a system of mirrors at Legrange Point L1, the point between the Earth and the Sun where the gravitational forces of both cancel each other out. The precise location of L1 was postulated by Josephy-Louis Lagrange in a prize-winning paper he wrote in 1772.
A team of researchers led by Ben Bromley, a theoretical astrophysicist at the University of Utah, has published a study that suggests dust particles situated at L1 could do the trick nicely. The amount of dust needed is calculated to be 109 kilograms, which is roughly a hundred times more mass than humans have sent into space to date.
According to the study, “Here, we revisit the reduction of sunlight received by Earth that results from the placement of dust at or near the inner Lagrange point, L1, lying directly between Earth and the Sun, including gravitational perturbations from the Moon and other planets. While unstable, these co-rotating orbits allow for the possibility of temporarily shading Earth. We start by assessing the shadows produced by various types of dust; then we numerically determine orbits that persist near L1, including the impact of radiation pressure and solar wind. Our main results are a connection between the quantity and quality of dust and the attenuation of sunlight at Earth on achievable orbits near L1. To compare with previous work, we target a reduction in solar irradiance of 1.8%, or 6 attenuation-days per year.”
Getting millions of tons of dust into space from the surface of the Earth would be a Herculean task (and would add untold quantities of greenhouse gas emissions to the atmosphere from all the rockets needed to get the job done). But Bromley and his team think they have a solution. Instead of sending materials from Earth into space, why not mine the materials needed from the moon and fire them into space using magnetic rail guns? The lower gravity of the moon would make the task much easier.
“A really exciting part of our study was the realization that the natural lunar dust grains are just the right size and composition for efficiently scattering sunlight away from Earth,” Bromley tells The Guardian.“Since it takes much less energy to launch these grains from the moon’s surface, as compared with an Earth launch, the ‘moonshot’ idea really stood out for us.” For the analysis of the composition and shape of the particles the researchers considered, see the two graphs below.
The Geoengineering Details Are The Hard Part
Getting the mining and rail gun equipment to the moon would be a “significant project,” Bromley admits. It might require positioning of a new space station near the L1 Lagrange point to “redirect packets of dust on to orbits that could provide shade for as long as possible.” Such an approach would act as a “fine-tuned dimmer switch, leaving our planet untouched,” Bromley said, an advantage over other solar geoengineering proposals that have raised concerns about the environmental impact of spraying reflective particles within the Earth’s atmosphere.
The moon dust would have to be continually propelled into space in order to take the edge off global heating, however, or risk a so-called “termination shock” that would follow the temporary cooling if it abruptly stopped and the world was left to rapidly heat up again. Bromley insisted that the research’s sci-fi idea is no substitute for the primary task of cutting planet heating emissions in the first place. “Nothing should distract us from reducing greenhouse gas emissions here on Earth,” he said. “Our strategy may just be a moonshot, but we should explore all possibilities, in case we need more time to do the work here at home.”
That’s all well and good for him to say, but may be rather naive when it comes to commercial and political realities. The odds are the fossil fuel industry would use this prospect as yet another excuse to just keep on keeping on when it comes to extracting, transporting, and burning their climate killing products.
Ted Parson, an expert in environmental law at UCLA, said the moon dust proposal was “fun, scientifically interesting speculation” that was unlikely to be put into practice, partially due to the larger cost and lack of control compared with Earth-based geoengineering options. “There seems to be a bit of an uptick of interest in space-based geoengineering schemes more broadly,” Parson told The Guardian. “They were long dismissed as wildly impractical due to technical and cost considerations, but my impression is that the ongoing reduction of launch costs is piquing people’s interest and strange ideas are bubbling around.”
Opponents of solar geoengineering, whether on Earth or in space, argue that it is an unhelpful and potentially dangerous distraction from the urgent imperative to transition away from burning fossil fuels. “The idea to mine the moon or near-Earth asteroids in order to artificially block parts of the sunlight is no solution to the ongoing and intensifying climate crisis,” said Frank Biermann, professor of global sustainability governance at Utrecht University. “What is needed are massive cutbacks in greenhouse gas emissions, which require rapid technological advancement and socioeconomic transitions. Mining the moon is not the answer that we need.”
Geoengineering is like hydrogen fuel cell cars — an idea that refuses to go away. It is welcomed by those who blithely assert that just when humanity is on the brink of extinction, we will magically find a way to science our way out of the inevitable disaster. That’s a tender and touching fantasy, but it won’t do anything to help us when we need it most.
The hard work of decarbonizing the global economy is the only thing that has any hope of succeeding. The only sensible thing to do is get on with it.
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