Illustration for article titled No, We Shouldnt Just Block Out the Sun
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We have a decade to sort out a big chunk of our carbon pollution problem. If we fail to do so, our chances at protecting the climate that allowed humans to thrive will slip away. That could lead to world leaders or a rogue billionaire taking the rather extreme measure of blocking the sun to cool things down. This isn’t some Lex Luther super villain idea, it’s something scientists are actively studying so we don’t dive headlong into a huge planetary experiment blind.

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The process known as solar radiation management (or SRM if you really want to geek out) is the most intensely planet-altering form of a broader set of unproven tools that fall under the banner of geoengineering. It would require injecting sun-reflecting particles in the Earth’s stratosphere in its most basic form or, if you’re a tech-loving former presidential candidate, deploying space mirrors.

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The idea has a certain seduction. It’s cheap (space mirrors aside). Though no humans have tested it, we know it would definitely cool things down based on what scientists have learned from studying volcanoes. And the alternative of unchecked climate change if we don’t get our act together isn’t exactly appealing.

But there are also plenty of issues, including not knowing the exact impacts it would have on other parts of the climate and the fact we may not being able to stop. The relative cost of a couple billion dollars a year really does mean, say, a bald billionaire who raked in $28 billion during the pandemic alone could do it. For a rogue state desperate for relief from the heat, there’s even more incentives to give it a go. Oh, and there’s no international rules about it. We’re talking some real Wild West shit here.

But hey, don’t take it from me. Earther reached out to experts to ask what keeps them up at night about solar radiation management. Their answers are below, lightly edited for clarity.


Paulo Artaxo

University of São Paulo Institute of Physics

Solar geoengineering poses major dangers in terms of global climate impacts. We will need more than a decade of good science to know if the technology could be applied, and which would be the negative side effects. Large changes in the hydrological cycle and in the ecosystems functioning will certain happen for some regions. Also governance is a nightmare, in a politically divided world. Major questions holds on the governance issue.

Who will implement and control the process? Which will be the role of developing countries in the control of the possible deployment? Can geoengineering be used to further increase the difference between rich and poor countries? Who pays the bill if something goes wrong? These are major questions, besides the scientific ones, that are unanswered.

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Kate Marvel

NASA Goddard Institute for Space Studies and Columbia University

We know a lot about the climate (why some regions are hot or cold, wet or dry, how atmospheric composition affects temperature and rainfall) but we don’t have perfect knowledge of this complex system- certainly not enough to deliberately start messing with it. And yes, I know that emitting lots of CO2 is also messing with the complex system of our planet, but I think we should focus on not doing that.

I think we could probably lower the average temperature by blocking the sun, but is the average temperature of the planet really all we care about? We have reason to think that deliberate geoengineering could affect regional precipitation patterns, and its effects on wild plant and crop growth (these things tend to like sunlight) are not well understood.

And here’s what really scares me: it might not matter. Geoengineering is pretty cheap, comparatively: a single country (or really a single billionaire) could probably do it unilaterally. And this poses problems. If Country A decides to begin geoengineering, and Country B experiences a weather disaster, I’m not sure scientific attribution studies will be any match for politicians in Country B, if they want to blame the As.

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Andy Parker

SRM Governance Initiative and University of Bristol

The answer is EVERYTHING. If you’re not unsettled by the prospect of sun-dimming, then you’ve not understood either what is being proposed or the reasons it’s being considered at all.

SRM would involve intervening in the climate system of the entire planet. Can we predict the impacts? And the side effects? Who would control it? What if a country uses it unilaterally? Could climate intervention lead to climate conflict?

Here you might be tempted to think “the risks are too big, we must and shall reject it.” But SRM is the only known way to quickly reduce global temperatures, and that might prove necessary. It might already be the only way to keep temperatures rises below 1.5 degrees Celsius, or to avoid any temperature-driven tipping points if they lurk between 1 degree Celsius and 2 degrees Celsius.

So SRM is like chemotherapy. It’s horrible, it’s risky, no one in their right mind would consider it… unless the alternative might be worse. And the alternative might well be worse. Once you face up to the fact that we live in a world where deliberately dimming the ****ing sun might be less risky than not doing it, you will have found cause for a few sleepless nights.

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Gernot Wagner

New York University

The biggest thing that keeps me up at night is the world slithering into geoengineering the way we just slid into covid-19: almost entirely unprepared, without having done the work. That means both the science but especially the hard policy and even harder political discussions. Nothing with geoengineering is predetermined. It takes smart, active policy to steer things into a productive, desirable direction.

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Paulo Araxto’s comment has been updated.

Managing editor, Earther

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