Cooling the Planet With a Space Shade Is Now Very Slightly More Plausible

I think it’s important to remember, as we see the warming climate break down our ecosystems and weather patterns, that we do have a sort of very limited “emergency break”, in the form of solar geoengineering. The term, in this context, refers to a few different actions that could be taken to lower Earth’s temperature without reducing greenhouse gas levels, by blocking or deflecting sunlight, before it can hit the surface of the planet, and turn into heat. The cheapest and most reliable method, at least in the short-term, is to release sulfate aerosols into the upper atmosphere, simulating a massive volcanic eruption, and reflecting sunlight to cool the planet. From what I can tell, there’s not much question that this would have a cooling effect. The problem is that it will also have other effects, which are less certain, on atmospheric chemistry and on ecosystems. Another one that’s often proposed is to make man-made surfaces white – rooftops, roads, parking lots – just make all of it more reflective. There’s zero question that this would have an effect, but it would be a fairly small effect, and it’s not clear to me what it would take to maintain that brightness. There are some others, which you can check out at first link, but today we’re going to talk about the “space-age” option.

See, if you want to reduce the sunlight hitting Earth’s surface, but you don’t want to have to worry about mucking with ecosystems and atmospheric chemistry, you can take the most literal option, and put a sun shade in space. From the University of Hawai’i:

One of the simplest approaches to reducing the global temperature is to shade the Earth from a fraction of the Sun’s light. This idea, called a solar shield, has been proposed before, but the large amount of weight needed to make a shield massive enough to balance gravitational forces and prevent solar radiation pressure from blowing it away makes even the lightest materials prohibitively expensive. Szapudi’s creative solution consists of two innovations: a tethered counterweight instead of just a massive shield, resulting in making the total mass more than 100 times less, and the use of a captured asteroid as the counterweight to avoid launching most of the mass from Earth.

“In Hawaiʻi, many use an umbrella to block the sunlight as they walk about during the day. I was thinking, could we do the same for Earth and thereby mitigate the impending catastrophe of climate change?” Szapudi said.

Incorporating a tethered counterbalance

Szapudi began with the goal of reducing solar radiation by 1.7%, an estimate of the amount needed to prevent a catastrophic rise in global temperatures. He found that placing a tethered counterbalance toward the Sun could reduce the weight of the shield and counterweight to approximately 3.5 million tons, about one hundred times lighter than previous estimates for an untethered shield.

While this number is still far beyond current launch capabilities, only 1% of the weight—about 35,000 tons—would be the shield itself, and that is the only part that needs to be launched from Earth. With newer, lighter materials, the mass of the shield can be reduced even further. The remaining 99% of the total mass would be asteroids or lunar dust used as a counterweight. Such a tethered structure would be faster and cheaper to build and deploy than other shield designs.

Today’s largest rockets can only lift about 50 tons to low Earth orbit, so this approach to solar radiation management would be challenging. Szapudi’s approach brings the idea into the realm of possibility, even with today’s technology, whereas prior concepts were completely unachievable. Also, developing a light-weight but strong graphene tether connecting the shield with the counterweight is crucial.

I know the billionaires have given space stuff something of a stink, but unlike fantasies of colonies on Mars or Venus, this is one way that improving our ability to do stuff in space could actually help with the climate crisis. There would certainly be pollution from launching any kind of space shade, and from getting to the point where we can do such a thing, but I don’t know how that would compare to the other options on the table.

As I’ve said before, this kind of geoengineering is dangerous, but probably unavoidable, because of long we’ve delayed action. It won’t matter much if we don’t also reduce greenhouse gas levels, but a slight drop in incoming sunlight could make things a lot easier, as long as we avoid the Futurama Solution. I guess the main question is – absent the kind of systemic political and economic change that I want to see, what will it take for “world leaders” to decide it’s time to shade the planet? What would it take for you to decide it’s time for that?

For me, I honestly don’t know. Doing it sooner might buy us some needed time, by delaying the melting of ice and thawing of permafrost, but the geopolitical and ecological ramifications worry me, because it seems like a foregone conclusion that the side effects would fall hardest on those with the least say in any of this. It sucks we’ve let things go so far, but I guess I’m glad that people are at least working out what it would take to shade the planet, and buy us a little more time.


  1. Pierce R. Butler says

    This reminds me of a comic book I read in the early-middle ’60s. Superman dropped in on a world ruled by a ruthless dictator, who had enslaved the entire population to reshape the planet into a sculpture of his own head. The dictator, forewarned by other space travelers of Superman’s vulnerabilities, had set up a space station with a giant blue lens aligned with its edges between his world and its yellow sun; with one command, the station pivoted the lens 90°, the sunlight turned green, and the mighty son of Krypton lost his powers and was forced to labor with pick and shovel alongside the locals. (Apparently the planetary portraiture was very high-rez.)

    I don’t remember how Supes tricked the dictator into disabling his orbital weapon so that the revolution could commence, only that he came back a while after the overthrow and saw the locals had continued their terraforming project, but to carve their planet to show Superman’s face instead of the dictator’s. Szapudiman’s scheme strikes me as equally plausible, except maybe he could auction the rights to have some jillionaire’s visage etched into the sunshade, smiling down backlit on all of us forevermore so we’d know who to thank for our salvation.

    Up, up, and away!

  2. Pierce R. Butler says

    Oops, apologies for the missing end-italics tag after “very”!

  3. says

    Well, there is one way in which this is more plausible than your scenario, or the proposed idea of a fresnel lens wider than the planet to diffuse the light – the shade needs to be much, much smaller. I’m not good with math, but it seems like blocking 1.7% of the light would mean the shade would be 1.7% the size of the lens/filter options.

    But yes – while I think we should continue investigating space travel (through orgs like NASA, not billionaire bullshit), I think we’re at least 98.3% more likely to see more terrestrial solutions deployed. If nothing else, pretty much any nation with the ability to fly at high altitude would be able to enact the sulfate aerosol concept. There are a number of multibillionaires who could also probably just make it happen. I’d expect someone doing that unilaterally to be attacked, or at least sanctioned, but that probably depends on more factors than I could list here.

  4. sonofrojblake says

    The remaining 99% of the total mass would be asteroids or lunar dust

    Which is nice and all but… while none of that stuff is down here in this gravity well, none of it is anywhere near where it’s needed, either. So by definition, as well the minimum SEVEN HUNDRED launches you’d need to put the shield up, you’d need an indeterminate number of additional launches of vehicles that could go and get some asteroid, collect it, and bring it back to where it’s needed.

    (Aside: in 2019 there were 102 successful space launches, from a total of 114 launches.)

    Consider also that if you’re going to do this in anything like a sensible timespan (i.e. less than many decades), you’re going to need a LOT of fuel, because you’re going to need to accelerate your counterweight out of whatever orbit it’s in at the moment, then decelerate it again when it’s in position. All of that fuel is coming out up of the earth’s gravity well, probably. (Ignoring fantasies of having a fuel factory on the moon, for instance).

    It would be interesting to identify the nearest NEO greater than 3.5 million tonnes, and work out how much fuel would be required to drive it from where it is to where it would need to be, given a few different desired timescales (the quicker you want it, the more fuel you need). You could then work out how many launches it would take to get all that fuel up off the earth and decanted into the tug boat. Then all the launches it would take to get the tug boat up there. Then all the additional fuel you’d need to drive the tug AND ALL THE FUEL to the asteroid.

    All this assumes the target isn’t actually orbiting closer to the sun… find a candidate there and you could conceivably solar-sail it out to the right orbit. You’d still need fuel and a tug, but maybe less?

    All of this sounds like techno-utopian fantasy, though. In my defence, I’ve watched way too much Star Trek.

  5. Pierce R. Butler says

    Abe Drayton @ # 3 – thanks for fixing my foo!

    The idea of some Tony Stark wannabe geoengineering a climate “remedy” strikes me as a cinematically bad idea, though I doubt even the billionaires with their own space programs (so far Musk, Bezos, & Branson – more working on it?) could make such preparations without a leak.

    Some nation might try that, though again word would likely get out and most other nations object. For any one country to try unilateral sulfate aerosolization would require some sort of Klimate Kissinger getting power behind the scenes – I don’t know of any such persons to worry about so far, but if the US elections go the wrong way next year…

  6. says

    If memory serves, someone near Putin was urging him to do it a while back, but it didn’t go anywhere. I think the most likely to try something like that solo would be the US, Russia, or China, but like I said I couldn’t begin to guess what would lead them to do that.

Leave a Reply

Your email address will not be published. Required fields are marked *