A new study published on Wednesday suggested that a deep-space umbrella of lunar dust could help slow the effects of climate change.
The study, published in the PLoS science journal, explains how a cloud of lunar dust launched between the Earth and the sun could block some of the solar radiation that warms the Earth.
This research offers new support for a lesser-known corner of solar geoengineering, a field that seeks to scatter or reflect solar rays before they hit the Earth.
The European Union is actively studying this idea, and the Biden administration has also started looking into it.
The White House Office of Science and Technology Policy has been reviewing comments on a five-year research project aimed at a “scientific assessment of solar and other rapid climate interventions” to curb global warming.
Solar geoengineering — like many other prospective planet-scale techniques to partially slow climate change — strikes many climate scientists as an enormous and unnecessary risk.
A group of 380 scientists signed an open letter last year calling on world governments to pledge to take solar geoengineering off the table.
The scientists’ concerns fell into three categories.
First, they argued that the risks of climate engineering are poorly understood and could destabilize weather patterns, with unknown impacts on global agriculture and the water cycle.
Next are the “moral hazard” objections: the scientists warned that hope for future moonshots like solar geoengineering could distract or disincentivize from far cheaper and more practical decarbonization efforts.
Finally, they contended that the current global governance system is not able to regulate the deployment of solar geoengineering technologies.
Geoengineering is particularly thorny because any country, corporation or private individual could theoretically launch an independent project — dragging the rest of the world behind them into experimental territory.
Last month, Mexico banned the controversial earth-based experimentation by startup Make Sunsets, which had been experimenting with releasing sulfur dioxide into the atmosphere above Baja California as an experimental means of reflecting heat.
However, advocates of the space-based approach hope it could sidestep some of the potential environmental consequences posed by Earth-based initiatives, which generally involve seeding the atmosphere with reflective particles.
According to experts, the idea of solar geoengineering has long been discussed but neglected by U.S. policymakers.
“These are old ideas, [but] I am glad they are getting more traction,” David Keith, who leads a solar geoengineering lab at Harvard, told The Hill in a statement.
Keith’s team wrote about this prospect in 2020, where he noted that such an effort would be “more ambitious than anything previously attempted in space.”
The Harvard research group wrote that such projects would require breakthroughs in space technologies, from asteroid mining to in-space fabrication and new, energy-efficient methods of launching rockets, research shows.
But the research team also argued that these technologies were far more accessible — and, therefore, more deserving of immediate attention — than ones often suggested by space boosters, like Jeff Bezos’ proposed space industries or Elon Musk’s Mars settlements.
He estimated that with a price of approximately $1 trillion, designing a program to cut solar radiation by just one percent would cost about as much as developing an American F-35 fighter jet — and far less than the economic cost of climate change.
The PLoS study, conducted by a team from the University of Utah, suggested a means of dropping costs further by using the moon as both a launch pad and a source of soil. The lunar launch site would eliminate the need for repeated flights out of Earth’s far-larger gravity well.
Researchers proposed that lunar dust would be a far more cost-effective strategy than launching dust from Earth. Their simulations found that blasting dust from Earth to the Lagrange Point — a point between the Earth and the sun where the gravitational forces are balanced — would rapidly drift out of place.
They found that lunar dust, by contrast, would be cheaper to put in place and would stay there longer.
According to the team, the big question was how effective the dust shield would be.
The answer was highly complex, because it depended on keeping a cloud of dust nearly a million miles away floating in a sufficiently steady position to cast a consistent shadow on the Earth. The study considers this further, indicating that setting up a shield at a stable Lagrange Point would be the best bet.
“It is astounding that the sun, Earth, and moon are in just the right configuration to enable this kind of climate mitigation strategy,” said Scott Kenyon, a Harvard’s Center for Astrophysics researcher.
The authors stressed that their study explored whether it was possible to use lunar dust particles as a sun shield — rather than whether doing so was feasible or even advisable.
Dr. Michael Mann, a climate scientist from the University of Pennsylvania, argued that geoengineering was a very risky fix to a problem with much easier answers.
Mann explained that the term “solar engineering” is misleading, as human society doesn’t have control over the sun. Instead, these frontier ideas are ways to manipulate our planetary environment in deep and fundamental ways.
Such interventions could produce more harm than good, he argued.
“While it is certainly true that reducing sunlight can cause cooling, it acts on a very different part of the climate system than carbon dioxide,” he told The Hill.
“And efforts to offset carbon dioxide-caused warming with sunlight reduction would yield a very different climate, perhaps one unlike any seen before in Earth’s history, with massive shifts in atmospheric circulation and rainfall patterns and possible worsening of droughts,” Mann added.
Then there is the possibility that more and more solar dimming will be required as the Earth continues to heat.
That could lead to the risk of “a catastrophic ‘termination shock’ wherein a century of pent-up global heating emerges within a decade,” Mann said.
“Some proponents insist we can always stop if we don’t like the result,” he continued. “Well yes, we can stop. Just like if you’re being kept alive by a ventilator with no hope of a cure, you can turn it off.”
He argued that there is a far simpler solution: reduce or eliminate the reliance on fossil fuels.