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Why Dimming the Sun Might be a Good Idea

“In the near future, climate modification will become necessary to maintain current climatic conditions,” wrote Soviet scientist Mikhail Budyko in 1974, responding to rising CO2 levels. In the decades following Budyko’s prediction, humanity has missed chance after chance to mitigate the catastrophic effects of climate change because of the actions of oil companies and the moral indifference of unchecked capitalism

Along with the new climatic conditions Budyko foresaw, the climate modifications are here too. Solar radiation management (SRM) is a theoretical plan to cool the earth by reflecting sunlight back into space. The most prominent and well-researched method of SRM is a strategy called stratospheric aerosol injection (SAI), where tiny particles would be deposited into the stratosphere to reflect solar radiation before it reaches the ground. SRM, through SAI or any other method, is a desperate measure, but one that reflects the desperation of our condition. Rising sea levels threaten to displace 1.4 billion people by 2060 while longer and more intense droughts will reduce food production, causing famine. Climate change is altering meteorological processes, destroying ecosystems, and triggering a mass extinction event.

Put bluntly by Andy Parker, director of the Solar Radiation Management Governance Initiative, “We live in a world where deliberately dimming the fucking sun might be less risky than not doing it.” While the potentially disastrous harms of SRM cannot be ignored, casting it aside is no longer an option. The international community needs to discuss and ultimately regulate SRM deployment, with emphasis on informed deliberation and environmental justice.  Humanity is facing suffering on an unprecedented scale and the cure may be worse than the disease. So, what does this discussion look like? 

First, the international community must lay the groundwork for informed conversation before any decisions are actually made; if scientists and government officials do not understand the precise benefits and drawbacks of SRM, they should not weigh its implementation. Yet earlier this year, Sweden canceled an experiment that would have tested technology for use in future small-scale SAI research. In 2019, the United States allocated only $4 million to the National Oceanic and Atmospheric Administration to research geoengineering as a whole, a far cry from the National Academies of Science, Engineering, and Medicine’s recommendation for $100-200 million in SRM research funds over the next five years. Without proper research into the realities of SRM, the technology will be sidelined while the world burns, or until one nation launches it out of desperation.

This latter concern adds to the urgency with which the international community needs to treat SRM. The financial cost of SAI is minor compared to the potential benefits of stalling climate change. Any nation that wishes to employ it could do so for as little as $2.25 billion each year over the first 15 years. “So if there’s pressure from the public to do something fast, my concern is that there will be no tools at hand other than stratospheric geoengineering,” noted chemist Frank Keutsch of Harvard’s Solar Geoengineering Research Program, in a recent interview. “But, over the years, as I see our lack of action on climate, I sometimes get quite anxious that this may actually happen.” If nothing else, the research required for an informed international discussion could unearth a catastrophic side effect of SRM that shuts down all consideration of it, preventing a frantic deployment. As geologist Daniel Schrag, a colleague of Keutsch, noted, “the highest priority for scientists is to figure out all the different ways this could go wrong.”

There is a lot that could go wrong with SAI, such as thinning the ozone layer, altering the nutrient cycle, and damaging human lungs. The most dire potential impact is a global rainfall reduction, which would disproportionately harm lower-income, less internationally powerful nations. For example, if SAI sparks drought in Asia and Africa, it would threaten the food security of billions of people. While the degree of this risk is far from certain, these disparate impacts would be a cruel repetition of the status quo pattern of climate injustice, where nations who are not responsible for climate change and who can do little to mitigate it are most acutely suffering from its effects. 

Yet the nations that could be most harmed by SAI are also the ones that stand to gain the most from it. The global cooling effect it causes may mitigate the strength and frequency of hurricanes in the Atlantic Ocean, improve crop productivity, and even reduce income inequality between nations by easing the GDP stratification climate change is causing. Facing financial collapse, mass migration, and physical erasure, low-income (and often low-lying) nations such as Belize, Bangladesh, and the Marshall Islands have a fundamental interest in any measure that can stave off climate change. SAI has the potential to revitalize them—or at least stave off existential threats. Their survival may be inextricable from its deployment. Between the intensifying effects of climate change and the risks and rewards of SAI, international deliberations must represent low-income nations at a rate disproportionate to their current political and financial power, as they most strongly experience the consequences of climate change actions and inaction. 

Still, international SRM discussions must exercise an extraordinary degree of caution when considering the technology’s deployment. Critics of the plan rightly note that it employs the same anthropocentric control of nature that got humanity into the mess of climate change in the first place. The intent is different, sure, but any individual, nation, or community that refuses to respect the limits of human knowledge risks colossal climate consequences. SRM is, by definition, human intervention in nature to alleviate the harms of human intervention in nature. Each layer of interference, however well-intentioned, introduces a new degree of uncertainty. There is no place for human hubris at the discussion table.

Unleashing drought through SRM deployment would be catastrophic, but writing off the strategy while billions suffer and are forced from their homes is its own great injustice. There is no avoiding our global predicament, no minimizing the irreversible damage humans have done to the planet and to each other. The future of climate policymaking will be defined by endless damage control, employing technologies and systems designed to correct the consequences of past actions. The international community needs to engage in honest, just, and humble deliberation to decide whether solar radiation management is a piece of the climate mitigation puzzle, else desperation forces the issue. Untested and undeveloped, SRM is a new frontier of humanity’s domination of the natural environment. It may or may not warrant deployment. But we no longer have the luxury of ignoring the question.

Photo by Mark Timberlake on Unsplash