20 ms·

Cooling the Earth with a cloud of small spacecraft near the inner Lagrange point

216 points by abecedarius 9y ago

deleted 9y ago
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- deleted 9y ago
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burke 9y ago
> It seems feasible that it could be developed and deployed in ≈25 years at a cost of a few trillion dollars, <0.5% of world gross domestic product (GDP) over that time. Much more optimistic numbers than I had previously guessed.
idbehold 9y ago
Since stopping CO2 levels from rising is nigh impossible, the only option left it seems is something drastic like this (I'm reminded of Futurama where they drop a giant ice cube into the ocean every once in a while). It has the added benefit of being able to be done without depending on everyone else changing their habits. I have a feeling that there are a bunch of these "plan B" solutions to our global climate change problem. It's that they are mostly just giving us more time before we have to actually deal with the problem. If the Atlantic Meridional Overturning Circulation ever comes to a halt then we are really screwed, so if there's anything which could prevent that from happening it might be worth the risk.
- hyperbovine 9y ago
  Unless you can stop the marine ecosystem from cratering (virtually a given if CO2 levels continue to rise unabated) it's all for naught. Enjoy your lack of oxygen.
  - idbehold 9y ago
    Agreed, these types of solutions are really just a stopgap (and a relatively short one at that). But that's always been the case. I mean, there's no beating entropy. Eventually the heat-death of the universe will make it, literally, all for naught.
    - bdamm 9y ago
      The difference between end of all time in however many tens of billions of years vs the economic collapse of human society in a handful of generations is a fairly major scale difference.
      - idbehold 9y ago
        Oh, there are plenty of things that will wipe out humans far earlier. I was just pointing out that there's always something threatening to destroy us.
        s_kilk 9y ago
        I just don't see the point in this. Knowing about the eventual heat-death of the universe doesn't make the immediate prospect of my family and I dying in a water riot any more palatable.
      - KGIII 9y ago
        Yeah, we've got less than two billion years before the Sun expands enough to cook off our atmosphere. I suspect we will be extinct before that, however. As a collective, we're not very bright.
        sslayer 9y ago
        Really we should just be focusing on building a time machine and re-populate the pre-human past. I imagine that no matter what happens, we could just populate infinite timelines (But we are more likely to already be on that exact timeline)
  - stcredzero 9y ago
    I'm highly dubious that all marine photosynthesis is going to be stopped easily. Do you have citations?
    - pixl97 9y ago
      On mobile so I'll let you search for it, but start at Wikipedia for anoxic oceanic event. You don't have to stop much photosynthesis for the oceans to produce huge amounts of deadly hydrogen sulfide
      - damnfine 9y ago
        The wiki does not support 'huge amounts', and makes some tenous connections to some localized events and worldwide extinction event ones, as do most of the people who bring this up. It makes it hard to have the same conversation if they are conflated. However, note the end of the wiki, where they state that the oxygenated state of the ocean currently is likely not the 'default' state of things if extrapolated beyond human history. It is certanly a concern. However there are ways to stimulate blooms, which may help serve to sequester carbon, and add oxygen in one fell swoop. Perhaps it is time to investigate the feasibility of such an action.
    - darkmarmot 9y ago
      https://s3.amazonaws.com/academia.edu.documents/32815525/wignallTwit1996.pdf?AWSAccessKeyId=AKIAIWOWYYGZ2Y53UL3A&Expires=1503698167&Signature=RolCR6KI65l2ni0ZTKbNJHMxgWI%3D&response-content-disposition=inline%3B%20filename%3DOcean_anoxia_and_the_end-Permian_mass_ex.pdf https://s3.amazonaws.com/academia.edu.documents/32815525/wig...
      - andai 9y ago
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- archagon 9y ago
  The problem with geo-engineering solutions to global warming is that they would require global consent. Anything else would be a drastic violation of human rights, and potentially a cause for massive conflict. We all have to share the same planet, and some peoples might be drastically opposed to (potentially) irreversible processes such as the scattering of chemicals in the atmosphere. Any "for the good of mankind" justification is almost beside the point.
  - idbehold 9y ago
    Wait, so everyone is allowed to contribute to global climate change without permission, but we need everyone's agreement to prevent it?
    - archagon 9y ago
      Unfortunately, yes? Nobody made the decision to contribute to global climate change; it just kind of happened as an emergent consequence of the discovery of oil. Whereas a single country deciding to permanently tint the sky is not going to go over well with the global community, probably to the point of tanks on borders and missiles at ready.
      - cortesoft 9y ago
        It wouldn't require global consent, just consent of the few global powers strong enough to do anything about it.
        archagon 9y ago
        Sure, but I think it'll be very difficult to get the US, China, and Russia to agree on something as drastic as this before catastrophic climate-related events start taking place. (And let's not forget all the other nations with nuclear missiles. The playing field is a lot more level these days, for better or worse.)
        9y ago
- stephengillie 9y ago
  The Earth's orbit is too circular and our axis isn't tilted enough. We're at the maximal energy absorbing posture. In 100,000 years, we'll need this greenhouse blanket to keep our ice planet warm.
  - Stratoscope 9y ago
    Those are some really interesting points; I wonder if you could elaborate a bit? Thanks! (Feel free to edit your comment to add detail instead of replying; keeps the thread shorter that way.)
  - putsteadywere 9y ago
    And if we solve this problem, then maybe we'll still have a technological civilization in 100,000 years to solve that one.
    - orthecreedence 9y ago
      Seems we already solved that one, just 100,000 years early.
  - undersuit 9y ago
    How does a rotating sphere, orbiting around another sphere every reach "maximal energy absorbing posture"?
    - MiguelHudnandez 9y ago
      I'm a layman, but my mental model suggests that tidal-lock would be the relationship that raises the energy most on the receiving body. An example of that concept would be Mercury. A tidally-locked body would have nearly 50% of its area "cold," in other words it is not radiating any heat from the primary heat source out into space. Only heat reaching the cold side from atmospheric convection or internal conduction would be able to reach space. In Mercury's case, the lack of significant atmosphere reduces the flow of heat from the warm side to the cold side. A spheroid with any given amount of surface area exposed to equal heat / cold has the highest chance of preserving equilibrium. If that logic is true, correcting Earth's axis tilt should slightly increase the amount of energy radiated away. That would also produce more consistent temperatures between the equators and poles (raising sea levels by reducing the amount of frozen water proportionally). Needless to say that would have nearly incalculable side effects.
- njarboe 9y ago
  I think a really hard limit on the max CO2 acceptable that most everyone would agree to would be where outside air starts to feel stuffy to humans. I have not found a good study on this but indoor air quality people say around 1000 ppm CO2 and you should start trying to increase ventilation. If the atmosphere gets too high it will be hard to keep indoor air below that without CO2 scrubbers. Over 750ppm(?) CO2 in the atmosphere and one gets the horrible situation where one goes inside a CO2 controlled space instead of outside to get "some fresh air". Edit: Here is a decent article on a study of some cognitive effects of CO2 levels (http://newscenter.lbl.gov/2012/10/17/elevated-indoor-carbon-dioxide-impairs-decision-making-performance/ http://newscenter.lbl.gov/2012/10/17/elevated-indoor-carbon-...). Actual study paper (https://ehp.niehs.nih.gov/1104789/ https://ehp.niehs.nih.gov/1104789/)
  - aetherson 9y ago
    We're at 400 ppm CO2 right now. So your feeling is that we'll probably start reducing carbon emissions once we double the amount of carbon in the air? 450 ppm is often held up as a catastrophic point of no return. I don't know if that's alarmist. Let's say it is! Maybe we'd have to get all the way to 600 ppm before it was genuinely a catastrophe. But I'm pretty confident that if we reach 700 ppm, we're fucked.
- gnopgnip 9y ago
  The total amount of CO2 in the atmosphere, and the amount produced and consumed by plants is very high compared to the amount produced by humans. Long term the solution is absolutely to reduce the CO2 produced by mankind through renewable energy, and reducing CO2 produced by agriculture. In the short term though carbon farming can sequester large amounts of carbon by growing on land that was previously desert, or the method mentioned in the linked page. Hopefully this slows down global warming enough to give humanity enough time to come up with a sustainable solution
  - bigbugbag 9y ago
    Just so you know, fossil fuels are a renewable energy on a large enough timescale. It's the massive rate of consumption and waste of them which is the issue. Switching to biofuel or solar or wind at the same massive consumption rate will not fix the issue.
    - andai 9y ago
      Do you mean that there do not exist any energy sources which are renewable at the rate we require, or that using such sources at the current / future rate would still be irresponsible for some reason?
    - nikdaheratik 9y ago
      > fossil fuels are a renewable energy on a large enough timescale No they're not, at least coal isn't because it was formed from trees and other heavy cellulose based plant matter that wasn't broken down by microbes millions of years ago, but would be broken down today. Oil and Methane may be "renewable" but not in a timeline worth considering. Switching to other methods of generation would fix the problem of climate change caused by the release of CO2. Other issues are definitely important, but not on the same level as unchecked global warming.
davesque 9y ago
I don't have the technical background to know if this is a pie-in-the-sky kind of thing, but it seems like an amazing idea. It reminds me of the "Icarus array" from the book "Echopraxia" by Peter Watts. Of course, this wouldn't harvest energy but just absorb it.
- nonbel 9y ago
  So, now the most egregiously greedy/evil plans from the Simpsons are being considered? >'The Sun Blocker was a device developed by Charles Montgomery Burns. As the name suggests, it was created to literally blot out the sun outside, in order to ensure Mr. Burns' electricity was sold in a monopoly, covering Springfield in perpetual darkness otherwise. The machine was extremely infamous alongside the theft of Springfield Elementary School's oil well for riling the Springfieldans' hatred of Mr. Burns, enough to want to murder him, especially Smithers, who had earlier been fired by Mr. Burns when the former protested against the plot and cited it was too heinous of a plan for even him to nominally support. [...] According to Mr. Burns, the Sun Blocker was conceived due to Mankind overall having an innate desire to destroy the sun, and that, due to the infeasibility of actually doing such an act, he settled for "the next best option."' http://simpsons.wikia.com/wiki/Sun_Blocker http://simpsons.wikia.com/wiki/Sun_Blocker
- sbierwagen 9y ago
  February 2001, "Ice and Mirrors", by Brenda Cooper and Larry Niven. Swarm of small mirrors used to cool a planet. Mentioned in this Nature article complaining about the cost: https://www.nature.com/news/2006/061030/full/news061030-6.html https://www.nature.com/news/2006/061030/full/news061030-6.ht... Predates Echopraxia by 13 years.
  - antisthenes 9y ago
    This is the space version of fusion, "just 20 years away" or "within our grasp" for the last 60 years. In fact, it may be even less feasible. Not to sound too much like a skeptic, but my bet is on terrestrial methods of mitigation, solar/wind/tidal, reforestation and, hopefully one day, fusion. Most people underestimate by several orders of magnitude how hard it is to launch something into space correctly.
jessaustin 9y ago
If this works, it will eventually be used by the military-industrial complex to pad the bottom line by arranging for rich nations to boss around poor nations on cynical pretexts. As with sanctions, they'll make a big show of saying, "We're so peace-loving that we'd never just bomb the fuck out of those starving kids without torturing them first... how do they like it when we turn this knob and their agriculture dies? Maybe they'll do as we say after about half of them have starved to death?"
- sp332 9y ago
  This is how big a shadow the Moon makes on the Earth. On a good day. https://twitter.com/WWUPlanet/status/896177474517716992 https://twitter.com/WWUPlanet/status/896177474517716992 And the Lagrange point is 4x further away than the Moon. You can cut the total amount of light hitting the earth, but you can't aim it like that. Edit: Here's the view from a satellite sitting at L1 https://epic.gsfc.nasa.gov/?date=2017-08-24 https://epic.gsfc.nasa.gov/?date=2017-08-24 and what it looks like when the Moon gets in the shot https://epic.gsfc.nasa.gov/galleries/2016/lunar_transit https://epic.gsfc.nasa.gov/galleries/2016/lunar_transit and a total eclipse from last year https://epic.gsfc.nasa.gov/galleries/2016/solar_eclipse https://epic.gsfc.nasa.gov/galleries/2016/solar_eclipse
  - jessaustin 9y ago
    I'm sure we don't have the technology to do this today, nor will we have it this century, but if TFA is ever practical then the weaponization thereof will be soon after. At that point artificial-light agriculture will probably be less expensive than today, but still more expensive than the outdoor kind.
    - tempestn 9y ago
      How would you aim the shadow? It's not a matter of technology; it's not physically possible to pinpoint a shadow from that distance.
      - 9y ago
xitrium 9y ago
What idiot called this "Feasibility of cooling the Earth with a cloud of small spacecraft near the inner Lagrange point" instead of "Solar Eclipses As A Service?"
- SoMisanthrope 9y ago
  LOL well played bro!
deft 9y ago
Why not a giant magnifying glass to concentrate the sun and increase temps on enemy territory?
bmcusick 9y ago
If you're going to put 20 million tons of perfectly identical gram-sized craft into orbit somewhere, it seems a lot more sensible to launch a factory to the Moon rather than launch all that mass from Earth. The CO2 added to the atmosphere from burning 2 billion tons of rocket fuel cannot be negligible.
- ef4 9y ago
  When you build them on earth, you aren't using "a factory", you're using a supply chain with thousands of factories and millions of people. A factory that can go from regolith all the way to spacecraft is still very speculative. As for 2 billion tons of rocket fuel, it's not trivial but it's something less than 5% of one year's current CO2 emissions, and we're talking about spreading it out over a couple decades.
- sp332 9y ago
  This is addressed in the paper. It's even addressed in the abstract of the paper. Edit: Second is a concept aimed at reducing transportation cost to $50/kg by using electromagnetic acceleration to escape Earth's gravity, followed by ion propulsion. The paper says that if there are rockets involved, they will be used outside of the atmosphere.
  - robotresearcher 9y ago
    > It's even addressed in the abstract of the paper. Where? edit: located below (italics added) thanks. The environmental costs of launch are considered. I can't see the environmental impact of manufacture considered explicitly, though. Abstract: If it were to become apparent that dangerous changes in global climate were inevitable, despite greenhouse gas controls, active methods to cool the Earth on an emergency basis might be desirable. The concept considered here is to block 1.8% of the solar flux with a space sunshade orbited near the inner Lagrange point (L1), in-line between the Earth and sun. Following the work of J. Early [Early, JT (1989) J Br Interplanet Soc 42:567–569], transparent material would be used to deflect the sunlight, rather than to absorb it, to minimize the shift in balance out from L1 caused by radiation pressure. Three advances aimed at practical implementation are presented. First is an optical design for a very thin refractive screen with low reflectivity, leading to a total sunshade mass of ≈20 million tons. Second is a concept aimed at reducing transportation cost to $50/kg by using electromagnetic acceleration to escape Earth's gravity, followed by ion propulsion. Third is an implementation of the sunshade as a cloud of many spacecraft, autonomously stabilized by modulating solar radiation pressure. These meter-sized “flyers” would be assembled completely before launch, avoiding any need for construction or unfolding in space. They would weigh a gram each, be launched in stacks of 800,000, and remain for a projected lifetime of 50 years within a 100,000-km-long cloud. The concept builds on existing technologies. It seems feasible that it could be developed and deployed in ≈25 years at a cost of a few trillion dollars, <0.5% of world gross domestic product (GDP) over that time.
barneygumble742 9y ago
Isn't this what Mr. Burns did on The Simpsons except for Springfield instead of Earth?
SoMisanthrope 9y ago
The earth doesn't need cooling. It's been cooling since the 1800's https://realclimatescience.com/2017/08/new-video-getting-started-with-unhiding-the-decline/ https://realclimatescience.com/2017/08/new-video-getting-sta... This project would be a tragic waste of resources that could better be used to accelerate research into safer nuclear reactors.
njarboe 9y ago
$50/kg to Earth orbit would be fantastic. One could get to a much higher exit point than the 5.5 km elevation (18,000 feet) they propose for even more efficient system. Seems like a great mega-project for China. They have the resources, drive, ambition, tech, and access to many 8 km+ mountains to build a launch tower on. Hopefully this would spur the US to partner with Chile and/or Argentina to build one on one of the ~7km peaks in South America. Denali is probably out of the question, but as military project, maybe it could be done.
- KGIII 9y ago
  Umm... I'm not sure it is politically feasible to build a rocket launching facility on Denali. That is gonna make a whole lot of people angry. You should see what happened when they put wind turbines on the much smaller mountains of Maine. Sort of related, I happen to like the looks with said turbines. There are still untainted vistas.
  - NegativeK 9y ago
    Is Denali worth it, given its remoteness, horrid weather patterns, and distance from the equator?
    - KGIII 9y ago
      From the little I know about rocket surgery, probably not. There are better places to launch from.
      - njarboe 9y ago
        From US soil? Not sure the US would put 10's to 100's of billions into a launcher and not have it in the US. Maybe the Panama Canal land grab route would be what would happen instead of Denali.
        KGIII 9y ago
        We'd probably use the current facilities. I suppose we could also try for Hawaii or Puerto Rico. The land grab is also an option, given the likely political climate if it reaches this point. My understanding is that closer to the equator is better, with some caveats.
kazinator 9y ago
With regard to stability, just use L4 and L5! Park some anchor objects at L4 and L5, and stretch a big tape-like net between those things, in the middle of which is the shading device. Problem solved! :)
xbryanx 9y ago
The American Geophysical Union is looking for feedback from its members on geo-engineering efforts like this right now. The draft statement is a good read: https://sciencepolicy.agu.org/comment-geoengineering/ https://sciencepolicy.agu.org/comment-geoengineering/
filleokus 9y ago
Can somebody who understands the subject (or have read the paper more carefully than me) say how the moment of the shadow on the earth would be? Would it be fixed on a part of the earth or move, and if it moves, how fast and in what "orbit". I.e, would some part of the earth get more (much more?) cloudy days if this would to be implemented?
- mabbo 9y ago
  You wouldn't see the shadows individually. The sun would just be a little bit (1.8%) less bright.
- ramidarigaz 9y ago
  The inner Lagrange point is always between the sun and the earth (by definition), so the "shadow" would always be centered on local "noon" and would pass the each longitude at the same time every day.
  - civilian 9y ago
    But the sun isn't a single point, it is big! In the same way that a pencil can have a sharp shadow but an office building will have a blurry shadow, the satellites would produce blurry shadows. I'm not sure of the dimensions of the inner Lagrange point-- I agree that the shadow would be centered on astronomical noon, but I think it would be so blurry, and have such a wide blur radius, as to be unnoticeable except as a change in absolute light.
mabbo 9y ago
It's also been speculated that the same idea could be used to have the opposite effect on Mars. A cloud of small satellites trying to push more sunlight towards the planet, thereby heating it up. It's all space-nerd talk for the moment, but none of the technology needed to achieve these goals is very far from reach today.
- antisthenes 9y ago
  In that case, neither is fusion, which is essentially free energy forever. It opens up the avenue for many more warming and CO2 mitigation techniques that are a reality today (e.g. desalination on a global scale and massive reforestation of Africa and the Amazon) As well as the ability to stop burning fossil fuels much quicker than transitioning to solar/wind.
  - eloff 9y ago
    It's interesting how you think it's possible to do massive reforestation in Brazil and Africa. Think about massive reforestation of Europe or the eastern USA and I think you'll see the fundamental problem with it. That land has already been put to other use (mostly agricultural use) and cannot simply be reforested. The government would have to repurchase the land from each individual land owner to do that which is not at all practical.
    - CPUstring 9y ago
      To be fair, France currently has more forests than it did a century ago.
redthrowaway 9y ago
So what happens if a big volcano goes off and we suddenly need that sunlight again? Not too easy to clear debris out of a Lagrange point.
phkahler 9y ago
This is a shit test.
- andai 9y ago
  It might be! lifeisstillgood 16 hours ago I remember a quote from a US geo-engineer to the effect of "half of my job is not to come up with geo-engineering solutions that will be used, but to show people that plan B is soooo extreme that they start taking plan A much more seriously" Citation needed I know but it has stuck with me
drc0 9y ago
simpsons did it https://metrouk2.files.wordpress.com/2011/03/article-1300967207614-0b51086100000578-330784_636x336.jpg https://metrouk2.files.wordpress.com/2011/03/article-1300967...
philipkglass 9y ago
If it were to become apparent that dangerous changes in global climate were inevitable, despite greenhouse gas controls, active methods to cool the Earth on an emergency basis might be desirable. ... It seems feasible that it could be developed and deployed in ≈25 years at a cost of a few trillion dollars, <0.5% of world gross domestic product (GDP) over that time. The "few trillion dollars" part is a problem. Not because it represents a particularly high cost scheme for neutralizing the warming part of AGW, but because it's so all-or-nothing. If you invest "only" $10 billion in this scheme the marginal abatement effects are going to be pretty close to zero, because so much of the cost is front-loaded into enabling technologies that will eventually deliver direct benefits. I refer the interested reader to the classic The Political Economy of Very Large Space Projects: http://www.jetpress.org/volume4/space.htm http://www.jetpress.org/volume4/space.htm With minor adjustments, it could be generalized as The Political Economy of Very Large Projects.
- digi_owl 9y ago
  In other words we are fucked because of incessant shorttermism...
- kanzure 9y ago
  > The "few trillion dollars" part is a problem. I am not particularly convinced that this requires a few trillion dollars. Is there some hard evidence that sunshades are impossible to deploy with less than $10 billion? http://diyhpl.us/~bryan/papers2/space/Self-deployed%20extremely%20large%20low%20mass%20space%20structures%20-%202007.pdf http://diyhpl.us/~bryan/papers2/space/Self-deployed%20extrem...
drawkbox 9y ago
Deflecting sunlight in orbit is interesting. Regarding deflecting light, for a long time white roofs have been pushed as a reflection mechanism[1] to deflect and lower energy costs thus reducing emissions. Though white roofs may actually increase warning in the way it reflects light onto other particles and doesn't help block it from coming into the atmosphere. Solar roofs capture it better and may be a better emissions lowering tool. Seems like a better idea to do it from space, unless of course it goes too far and is difficult to control. [1] https://www.theguardian.com/environment/2011/oct/27/white-roofs-global-warming https://www.theguardian.com/environment/2011/oct/27/white-ro...
- wellboy 9y ago
  This seems really viable. Deflecting is still better than absorbing on the roof top, since roof top means 100% warmth absorption and deflection always less than 100%, probably only a fraction of that.
  - sliken 9y ago
    Your assuming that the atmosphere is more transparent to infrared (from a hot roof) then optical ranges (from a white roof).
    - jwilk 9y ago
      No? The atmosphere is more transparent to sunlight than to IR, thanks to greenhouse gases. That's why absorbent roofs heat the Earth more than reflective roofs.
    - wellboy 9y ago
      No. As an a example, I'm assuming that hot roofs absorb 70% of the incoming energy and reflect 30%, where reflectig roofs absorb 10% and reflect 90%. These numbers can be a bit different, but I'm pretty sure that hot roofs absorb a multiple of energy compared to reflecting roofs. Makes sense?
hughes 9y ago
> there is no fundamental reason why launch from Earth by linear acceleration to escape velocity of 11.2 km/sec should not be possible ok... even if you build it 5km in the sky, a 1km long launch rail would still apply 6,000 Gs of acceleration. Good luck designing a spacecraft that can survive that.
- sliken 9y ago
  Or don't waste 5km and make the tube 5km. The acceleration drops to 1282G. Digging a 1km hole drops it to 1000G or so. Not really that much. About the acceleration a woodpecker head gets, less than a baseball being hit by a bat, or what a wrist watch can withstand. Under 1/10th that of the electronics in an artillery shell.
mchannon 9y ago
This strategy, to get rid of some sunlight, doesn't fix our problem with CO2. In fact, it's likely to make the problem worse. Our planet has two primary natural methods for lowering atmospheric CO2. One, natural weathering, is not impacted with this strategy. The other, plantlife, is absolutely affected. If you were to take 10% of sunlight away from Earth, then it logically follows that plants would get 10% less sunlight to convert CO2 into starches and H2O into oxygen. The resource you're trying to constrain, in the name of fighting effects of rising CO2 levels, is the very resource you need in order to fight rising CO2 levels. Sure, blocking or deflecting some light might lower Earth's temperatures temporarily, but you'd exacerbate CO2 levels semi-permanently. We, as a community, need to come to the realization that our CO2 problem is not strictly a temperature problem.
- taberiand 9y ago
  There isn't going to be one single solution, but reducing incoming sunlight by a small percentage (1-2%) could be a cost effective part of a multi-layer approach.
- koverstreet 9y ago
  Amount of sunlight is not the limiting factor on plant growth in most places. In fact, it's often the opposite - plants shut down respiration during midday to limit water loss because it's too hot.
  - mchannon 9y ago
    I imagine "most places" refers to most places on land, which is less than 20% of the range of where plants grow. Ocean-based plantlife is the workhorse on this planet, and I would argue that the lion's share is absolutely constrained by available sunlight. Further, there's a substantial difference between "respiration" and absorption of sunlight. Pineapple plants, for instance, only "breathe" at night.
    - tlb 9y ago
      Plant life in the oceans is mainly limited by minerals, especially iron. That's why the oceans aren't green and slimy. Dumping iron powder in will usually cause an algae bloom, which eventually die and take the carbon they fixed to the bottom, so seeding the oceans with iron is a potential way of reducing CO2 in the atmosphere. Of course, like any large-scale meddling, there will be collateral damage.
gdubs 9y ago
I'm all for exploring solutions, but I also wonder about the behavioral economics at play when people "feel" like a geo-engineering solution is inevitable. In other words, how much does believing we will inevitably engineer our way out of the problem keep us from making the hard choices that may be necessary.
- svachalek 9y ago
  Who is the "us" that needs to make hard choices? Those that are seriously impacted by climate change and those that stand to benefit from the status quo are very disjoint sets, and the latter have shown quite an aptitude for persuading the former not to worry about it. The time for making those hard choices is quickly passing by without any significant motion. It's not time to give up yet but it's also not a good idea to just assume people are going to come around on this.
- fleitz 9y ago
  All solutions are geo-engineering... Exactly what kind of solution are all the things that are recommended to do to lower global CO2? The only difference is the current recommendations are inefficient and take a long time.
  - andai 9y ago
    And are at odds with greed / desire for comfort and luxury.
    - fleitz 9y ago
      Exactly, which is why the whole thing is stupid and isn't going to happen. Enviros: You can enjoy longer summers and shorter winters, or you can be poor. Sane people: Longer summers and shorter winters sounds pretty good to me.
deleted 9y ago
[deleted]
alkonaut 9y ago
Wouldn't earth based reflection be a lot simpler? E.g artificial clouds/ice/etc to reflect sunlight off the planet?
- bigbugbag 9y ago
  Like polar ice ? this would be simpler for sure but it would require very difficult things to attain such as having people relinquish their air conditioning, stopping capitalism and consumerism, changing the global industrial process, diminishing our energy consumption, replacing the current political systems with democratic ones, returning to ways of producing food that do not cause soil infertility.
  - alkonaut 9y ago
    Exactly like polar ice. The problem as you point out is that polar ice is reducing which just makes it worse. And obviously this whole discussion about technological solutions is due to the fact that all those things you list seem to be impossible or happening too slowly. I doubt artificial ice is the easiest solution, but e.g artificial clouds could be perhaps.
    - andai 9y ago
      I saw something on TV a few years ago about a project to make boats which would spray a fine mist high into the atmosphere, ie. create artificial clouds to reduce the heating of the earth.
- lagadu 9y ago
  That's what stratospheric sulfate aerosols[0] are. Same stuff the industry already dumps into the atmosphere but dumped way higher in low amounts and easy to reverse: you can just shut it down and the effects fade over the course of the following year. [0] https://en.wikipedia.org/wiki/Stratospheric_aerosol_injection_(climate_engineering) https://en.wikipedia.org/wiki/Stratospheric_aerosol_injectio...
lifeisstillgood 9y ago
I remember a quote from a US geo-engineer to the effect of "half of my job is not to come up with geo-engineering solutions that will be used, but to show people that plan B is soooo extreme that they start taking plan A much more seriously" Citation needed I know but it has stuck with me
gene-h 9y ago
This project requires millions of square kilometers of high tech satellites. If we could make millions of square kilometers of high tech satellites then we could probably make millions of square kilometers of solar panels here on earth, and not put CO2 into the atmosphere in the first place.
- andai 9y ago
  "The future is already here — it's just not very evenly distributed." William Gibson The space based sunglasses would shield the entire earth. I think it would be more difficult to get millions of square kilometers of solar panels evenly distributed.
whataretensors 9y ago
Does anyone have links to a good recent research paper on climate change? With modeling details and dataset. I've looked around but it's difficult to find the best/most recent knowledge.
anotherbrownguy 9y ago
I don't understand why people are still obsessed with "global warming". The political proponents of it have already changed it to "climate change" after global temperature stopped rising for a decade and it's been almost two decades now. I would be much worried about "global cooling" i.e. another ice age. A couple of degree increase over the next hundred years (which is their worst case estimate based on the most advanced models, even though no model has been able to predict anything, only fit historical data) will change nothing. Sea levels will probably rise by a few feet and people living in their beach houses will have to find another vacation spot in 20 years after they notice that the sea has been coming closer to their house since the last decade. Ice age is just as unpredictable (except they don't even have a make-believe explanation for it) and could start any time giving us very little time to prepare. If we want humans to suffer less because of it, the least we should do is try to give over a billion people who have no access to electricity some way to make sure that they will be able to heat their houses if it's cold, like most of the developed world can... in addition, meanwhile, they can enjoy clean drinking water, washing machines, industries etc.
- wellboy 9y ago
  Many U.S. coast cities will become submerged when sea-levels rise by several feet. This is not the omly effect, particularly countries in the middle east will dry out, leading rural inhabitants to gravitate towards in excess of their capacities, leading to destabilised countries. This has already happened with Syria and millions if refugees, now wait for the remaining countries to follow with hundreds of millions of refugees in the next 100 years. Naturally, even heavier hurricanes, more devastating floods will happen. Keep in mind, a rise of only 6 degress fahrenheit, means a rise of 20 degrees fahrenheit in some areas and less in others. This is catastrophic for the areas that are among the ones with bad luck and will induce mass migration/fleeing.
- citizen13384 9y ago
  Source?
- tempestn 9y ago
  Most of your assertions here are incorrect. You don't need a particularly complex model to show that if more energy is absorbed by the earth than is radiated, which is the case due to greenhouse gasses in the atmosphere, the temperature will rise until it returns to a steady state at a higher temperature. This means that even if CO2 emissions stop immediately (which obviously they won't), the temperature will continue rising for a period of time (some decades). A 2 degree rise is considered to be the absolute limit without likely catastrophic consequences. It is certainly not the worst case. Sea levels could certainly rise by more than you claim, but sea level rise is far from the only problem. See here for instance: http://nymag.com/daily/intelligencer/2017/07/climate-change-earth-too-hot-for-humans.html http://nymag.com/daily/intelligencer/2017/07/climate-change-... If you're being honest about your introduction, that you don't understand why people are concerned about climate change, then that's a start. If you're instead trying to convince people of your point of view, please provide evidence for your assertions.
amelius 9y ago
Don't we need the photons to convert CO2 back into O2 through photosynthesis?
civilian 9y ago
> 3 trillion dollars This is why we need a space elevator! Costs would be reduced from $40k / kg to ~$400/kg. I spoke to an engineer at a space-focused company about space elevators. He, unfortunately, burst my bubble. While the elevator itself might be feasible, he thinks that countries would never let an asteroid large enough to act as a counterweight, with thrusters large enough to move it attached, enter Earth's orbit. The potential of it being used as a catastrophic weapon is just too dangerous.
- XR0CSWV3h3kZWg 9y ago
  We'd also need to advance material science and logistics quite a bit. It sounds like carbon fiber has the tensile strength, but we can't make it in near the length nor quality we'd need for a space elevator. The elevator would need to avoid or divert space junk. And we haven't actually practiced asteroid capture, much less orbit keeping on a scale that large.
nickt 9y ago
Sunstorm [1] by Arthur C. Clarke & Stephen Baxter, obliquely touches on this though with added aliens and a larger threat from the sun. [1] https://www.goodreads.com/book/show/35815.Sunstorm https://www.goodreads.com/book/show/35815.Sunstorm
godshatter 9y ago
I'm not against geo-engineering as a general concept, even though I don't personally buy into the most alarmist of the climate change scenarios. If we do do some kind of project like this, I would want to have a counter in place in case it does more harm than good, as a general rule of thumb. I would want that factored into the cost and preparations in place for just such an eventuality before committing to such a course. In this case, though, it seems relatively trivial - it seems like it's more work to keep them in place then to have them scatter to the (solar?) winds. Once they've moved out of the Lagrange point, then they become a non-issue. All we've lost is the money to put them there and the materials. Compared to some of the other ideas I've heard, this appears to be much safer.
xhasid 9y ago
Would it possible to aim to have these satellites shade only one or both of the poles? That could solve the problem of reduced sunlight for plants. (Among other issues.)
- tempestn 9y ago
  ISTM it would be difficult since the sun isn't a point source. Fortunately, as other comments have mentioned, sunlight is not the limiting factor for plant growth in most situations.
StefanKovachev 9y ago
YOU ARE SUCH AN IDIOTS! ... BLAH BLAH. IM ANGRY HOW SUCH AN INTELLIGENT PEOPLE CAN RATE THIS CURRENTLY IMPOSSIBLE IDEA! THE MAIN POINT IS THAT YOU NEED TO STOP THE SAME AMOUNT OF SUN ENERGY... HOW?! BULLSHIT! IDIOTS!...
SCAQTony 9y ago
How would a "cloud" at the Lagrange point be removed in the event of a global cool down or "black swan" event occurred?
- throwaway7645 9y ago
  My first thought as well.
- cookingrobot 9y ago
  From the article, the L1 Lagrange point isn't stable, it's a saddle. In the plan described here, the craft would be actively controlled to adjust how much light they're diverting and at what angle in order to stay balanced at the Lagrange. If the steering system is turned off all the reflectors would harmlessly blow away.
spenrose 9y ago
"They would weigh a gram each, be launched in stacks of 800,000, and remain for a projected lifetime of 50 years within a 100,000-km-long cloud. The concept builds on existing technologies. It seems feasible that it could be developed and deployed in ≈25 years at a cost of a few trillion dollars, <0.5% of world gross domestic product (GDP) over that time." Oh FFS. If we have a few $trillion to devote to global warming, we can enormously reduce it using known technologies. There is an important clue in this spectacular self-own to the emotional allegiances of the people who get excited about ideas such as this one.
- devrandomguy 9y ago
  If I was given a few $trillion to solve atmospheric CO2/CH4, I would move mining to the moon, and move manufacturing and agriculture into orbit. Then smother the Earth-side economy with cheap/free stuff to discourage the remaining entrenched industry, and offer habitat space to anyone who prefers doing physical work for a living, over living in a highly regulated paradise on UBI + patreon. For perspective, Gerard K. O'Neil gave a ballpark estimate of $31B (correction: $31B in 1972 dollars, $172B in 2013 dollars) for a v1 O'Neil cylinder made of steel. http://www.nss.org/settlement/physicstoday.htm http://www.nss.org/settlement/physicstoday.htm
- sliken 9y ago
  How about just invest in a solar powered way to make something useful from CO2 in the atmosphere. Like say a brick. We could make roads and buildings out of it.
  - andai 9y ago
    I think trees stole your idea about 400 million years ago.
    - sand500 9y ago
      Yep, look up carbon sequestration.
AlexCoventry 9y ago
If the authors are around, you're missing some backslashes before your dollar signs, here: http://www.pnas.org/content/103/46/17184.full#sec-3 http://www.pnas.org/content/103/46/17184.full#sec-3
patrickdavey 9y ago
I'd argue that the more energy you use, the more comfortable your life is. I'd also argue that energy use (at the moment) is pretty linked to how much CO2 you emit. A lot of the biggest emitters live in democracies. So, how do you get the majority of the population to vote in politicians who are going to make their lives less comfortable (by taxing / controlling / lessening the amount of CO2 they use)? Frankly I reckon we, as a civilization, are going to dither and procrastinate up until the point it's far far far too late to do anything meaningful, and then people will try jump on the geoengineering to hack things into place. There was a nice piece in the book "This changes everything" where they were talking about geoengineering. I'll paraphrase, but basically someone said "we'll just alter things in this way", and someone else said "that'll mean droughts in my country". Fun times ahead. If you haven't read it yet, I recommend "Sustainable Energy Without the Hot Air" [0] to get an idea of just how much less energy we need to use if we want to get by with just renewables. I really hope we can get there! [0] https://www.withouthotair.com/ https://www.withouthotair.com/
mishkovski 9y ago
One option is to find a way to decrease human population voluntarily. That will reverse human related climate change in more natural and comprehensive way.
- deleted 9y ago
  [deleted]
SubiculumCode 9y ago
Any form of geoengineering that is outside of earth mskes me nervous. Removing or altering its effect might be precluded if society breaks down (e.g.after a nucleur war)
aurora- 9y ago
Well, this could give a good reason to build a Moon base. Instead of launching all that mass from the Earth (~20 million tons), the sunshade satellites could be launched from the Moon, using an electromagnetic launcher, for just a few dollars per kg. Building a Lunar base would start with seed factories, that would then build the base, which would make the launcher and the sunshades. The amount of material needed to start the seed factories should be under 20,000 tons, or 0.1% of the mass needed to launch the sun shades directly from Earth.
Nomentatus 9y ago
"A major technical hurdle to be overcome is the instability of the orbit, which is at a saddle point." Tether from the lunar surface, through the Lagrange point.

216 points by abecedarius 9y ago

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burke 9y ago

> It seems feasible that it could be developed and deployed in ≈25 years at a cost of a few trillion dollars, <0.5% of world gross domestic product (GDP) over that time. Much more optimistic numbers than I had previously guessed.

idbehold 9y ago

Since stopping CO2 levels from rising is nigh impossible, the only option left it seems is something drastic like this (I'm reminded of Futurama where they drop a giant ice cube into the ocean every once in a while). It has the added benefit of being able to be done without depending on everyone else changing their habits. I have a feeling that there are a bunch of these "plan B" solutions to our global climate change problem. It's that they are mostly just giving us more time before we have to actually deal with the problem. If the Atlantic Meridional Overturning Circulation ever comes to a halt then we are really screwed, so if there's anything which could prevent that from happening it might be worth the risk.

hyperbovine 9y ago
Unless you can stop the marine ecosystem from cratering (virtually a given if CO2 levels continue to rise unabated) it's all for naught. Enjoy your lack of oxygen.
- idbehold 9y ago
  Agreed, these types of solutions are really just a stopgap (and a relatively short one at that). But that's always been the case. I mean, there's no beating entropy. Eventually the heat-death of the universe will make it, literally, all for naught.
  - bdamm 9y ago
    The difference between end of all time in however many tens of billions of years vs the economic collapse of human society in a handful of generations is a fairly major scale difference.
    - idbehold 9y ago
      Oh, there are plenty of things that will wipe out humans far earlier. I was just pointing out that there's always something threatening to destroy us.
      - s_kilk 9y ago
        I just don't see the point in this. Knowing about the eventual heat-death of the universe doesn't make the immediate prospect of my family and I dying in a water riot any more palatable.
    - KGIII 9y ago
      Yeah, we've got less than two billion years before the Sun expands enough to cook off our atmosphere. I suspect we will be extinct before that, however. As a collective, we're not very bright.
      - sslayer 9y ago
        Really we should just be focusing on building a time machine and re-populate the pre-human past. I imagine that no matter what happens, we could just populate infinite timelines (But we are more likely to already be on that exact timeline)
- stcredzero 9y ago
  I'm highly dubious that all marine photosynthesis is going to be stopped easily. Do you have citations?
  - pixl97 9y ago
    On mobile so I'll let you search for it, but start at Wikipedia for anoxic oceanic event. You don't have to stop much photosynthesis for the oceans to produce huge amounts of deadly hydrogen sulfide
    - damnfine 9y ago
      The wiki does not support 'huge amounts', and makes some tenous connections to some localized events and worldwide extinction event ones, as do most of the people who bring this up. It makes it hard to have the same conversation if they are conflated. However, note the end of the wiki, where they state that the oxygenated state of the ocean currently is likely not the 'default' state of things if extrapolated beyond human history. It is certanly a concern. However there are ways to stimulate blooms, which may help serve to sequester carbon, and add oxygen in one fell swoop. Perhaps it is time to investigate the feasibility of such an action.
  - darkmarmot 9y ago
    https://s3.amazonaws.com/academia.edu.documents/32815525/wignallTwit1996.pdf?AWSAccessKeyId=AKIAIWOWYYGZ2Y53UL3A&Expires=1503698167&Signature=RolCR6KI65l2ni0ZTKbNJHMxgWI%3D&response-content-disposition=inline%3B%20filename%3DOcean_anoxia_and_the_end-Permian_mass_ex.pdf https://s3.amazonaws.com/academia.edu.documents/32815525/wig...
    - andai 9y ago
      <Error> <Code>AccessDenied</Code> <Message>Request has expired</Message>
archagon 9y ago
The problem with geo-engineering solutions to global warming is that they would require global consent. Anything else would be a drastic violation of human rights, and potentially a cause for massive conflict. We all have to share the same planet, and some peoples might be drastically opposed to (potentially) irreversible processes such as the scattering of chemicals in the atmosphere. Any "for the good of mankind" justification is almost beside the point.
- idbehold 9y ago
  Wait, so everyone is allowed to contribute to global climate change without permission, but we need everyone's agreement to prevent it?
  - archagon 9y ago
    Unfortunately, yes? Nobody made the decision to contribute to global climate change; it just kind of happened as an emergent consequence of the discovery of oil. Whereas a single country deciding to permanently tint the sky is not going to go over well with the global community, probably to the point of tanks on borders and missiles at ready.
    - cortesoft 9y ago
      It wouldn't require global consent, just consent of the few global powers strong enough to do anything about it.
      - archagon 9y ago
        Sure, but I think it'll be very difficult to get the US, China, and Russia to agree on something as drastic as this before catastrophic climate-related events start taking place. (And let's not forget all the other nations with nuclear missiles. The playing field is a lot more level these days, for better or worse.)
        9y ago
stephengillie 9y ago
The Earth's orbit is too circular and our axis isn't tilted enough. We're at the maximal energy absorbing posture. In 100,000 years, we'll need this greenhouse blanket to keep our ice planet warm.
- Stratoscope 9y ago
  Those are some really interesting points; I wonder if you could elaborate a bit? Thanks! (Feel free to edit your comment to add detail instead of replying; keeps the thread shorter that way.)
- putsteadywere 9y ago
  And if we solve this problem, then maybe we'll still have a technological civilization in 100,000 years to solve that one.
  - orthecreedence 9y ago
    Seems we already solved that one, just 100,000 years early.
- undersuit 9y ago
  How does a rotating sphere, orbiting around another sphere every reach "maximal energy absorbing posture"?
  - MiguelHudnandez 9y ago
    I'm a layman, but my mental model suggests that tidal-lock would be the relationship that raises the energy most on the receiving body. An example of that concept would be Mercury. A tidally-locked body would have nearly 50% of its area "cold," in other words it is not radiating any heat from the primary heat source out into space. Only heat reaching the cold side from atmospheric convection or internal conduction would be able to reach space. In Mercury's case, the lack of significant atmosphere reduces the flow of heat from the warm side to the cold side. A spheroid with any given amount of surface area exposed to equal heat / cold has the highest chance of preserving equilibrium. If that logic is true, correcting Earth's axis tilt should slightly increase the amount of energy radiated away. That would also produce more consistent temperatures between the equators and poles (raising sea levels by reducing the amount of frozen water proportionally). Needless to say that would have nearly incalculable side effects.
njarboe 9y ago
I think a really hard limit on the max CO2 acceptable that most everyone would agree to would be where outside air starts to feel stuffy to humans. I have not found a good study on this but indoor air quality people say around 1000 ppm CO2 and you should start trying to increase ventilation. If the atmosphere gets too high it will be hard to keep indoor air below that without CO2 scrubbers. Over 750ppm(?) CO2 in the atmosphere and one gets the horrible situation where one goes inside a CO2 controlled space instead of outside to get "some fresh air". Edit: Here is a decent article on a study of some cognitive effects of CO2 levels (http://newscenter.lbl.gov/2012/10/17/elevated-indoor-carbon-dioxide-impairs-decision-making-performance/ http://newscenter.lbl.gov/2012/10/17/elevated-indoor-carbon-...). Actual study paper (https://ehp.niehs.nih.gov/1104789/ https://ehp.niehs.nih.gov/1104789/)
- aetherson 9y ago
  We're at 400 ppm CO2 right now. So your feeling is that we'll probably start reducing carbon emissions once we double the amount of carbon in the air? 450 ppm is often held up as a catastrophic point of no return. I don't know if that's alarmist. Let's say it is! Maybe we'd have to get all the way to 600 ppm before it was genuinely a catastrophe. But I'm pretty confident that if we reach 700 ppm, we're fucked.
gnopgnip 9y ago
The total amount of CO2 in the atmosphere, and the amount produced and consumed by plants is very high compared to the amount produced by humans. Long term the solution is absolutely to reduce the CO2 produced by mankind through renewable energy, and reducing CO2 produced by agriculture. In the short term though carbon farming can sequester large amounts of carbon by growing on land that was previously desert, or the method mentioned in the linked page. Hopefully this slows down global warming enough to give humanity enough time to come up with a sustainable solution
- bigbugbag 9y ago
  Just so you know, fossil fuels are a renewable energy on a large enough timescale. It's the massive rate of consumption and waste of them which is the issue. Switching to biofuel or solar or wind at the same massive consumption rate will not fix the issue.
  - andai 9y ago
    Do you mean that there do not exist any energy sources which are renewable at the rate we require, or that using such sources at the current / future rate would still be irresponsible for some reason?
  - nikdaheratik 9y ago
    > fossil fuels are a renewable energy on a large enough timescale No they're not, at least coal isn't because it was formed from trees and other heavy cellulose based plant matter that wasn't broken down by microbes millions of years ago, but would be broken down today. Oil and Methane may be "renewable" but not in a timeline worth considering. Switching to other methods of generation would fix the problem of climate change caused by the release of CO2. Other issues are definitely important, but not on the same level as unchecked global warming.

davesque 9y ago

I don't have the technical background to know if this is a pie-in-the-sky kind of thing, but it seems like an amazing idea. It reminds me of the "Icarus array" from the book "Echopraxia" by Peter Watts. Of course, this wouldn't harvest energy but just absorb it.

nonbel 9y ago
So, now the most egregiously greedy/evil plans from the Simpsons are being considered? >'The Sun Blocker was a device developed by Charles Montgomery Burns. As the name suggests, it was created to literally blot out the sun outside, in order to ensure Mr. Burns' electricity was sold in a monopoly, covering Springfield in perpetual darkness otherwise. The machine was extremely infamous alongside the theft of Springfield Elementary School's oil well for riling the Springfieldans' hatred of Mr. Burns, enough to want to murder him, especially Smithers, who had earlier been fired by Mr. Burns when the former protested against the plot and cited it was too heinous of a plan for even him to nominally support. [...] According to Mr. Burns, the Sun Blocker was conceived due to Mankind overall having an innate desire to destroy the sun, and that, due to the infeasibility of actually doing such an act, he settled for "the next best option."' http://simpsons.wikia.com/wiki/Sun_Blocker http://simpsons.wikia.com/wiki/Sun_Blocker
sbierwagen 9y ago
February 2001, "Ice and Mirrors", by Brenda Cooper and Larry Niven. Swarm of small mirrors used to cool a planet. Mentioned in this Nature article complaining about the cost: https://www.nature.com/news/2006/061030/full/news061030-6.html https://www.nature.com/news/2006/061030/full/news061030-6.ht... Predates Echopraxia by 13 years.
- antisthenes 9y ago
  This is the space version of fusion, "just 20 years away" or "within our grasp" for the last 60 years. In fact, it may be even less feasible. Not to sound too much like a skeptic, but my bet is on terrestrial methods of mitigation, solar/wind/tidal, reforestation and, hopefully one day, fusion. Most people underestimate by several orders of magnitude how hard it is to launch something into space correctly.

jessaustin 9y ago

If this works, it will eventually be used by the military-industrial complex to pad the bottom line by arranging for rich nations to boss around poor nations on cynical pretexts. As with sanctions, they'll make a big show of saying, "We're so peace-loving that we'd never just bomb the fuck out of those starving kids without torturing them first... how do they like it when we turn this knob and their agriculture dies? Maybe they'll do as we say after about half of them have starved to death?"

sp332 9y ago
This is how big a shadow the Moon makes on the Earth. On a good day. https://twitter.com/WWUPlanet/status/896177474517716992 https://twitter.com/WWUPlanet/status/896177474517716992 And the Lagrange point is 4x further away than the Moon. You can cut the total amount of light hitting the earth, but you can't aim it like that. Edit: Here's the view from a satellite sitting at L1 https://epic.gsfc.nasa.gov/?date=2017-08-24 https://epic.gsfc.nasa.gov/?date=2017-08-24 and what it looks like when the Moon gets in the shot https://epic.gsfc.nasa.gov/galleries/2016/lunar_transit https://epic.gsfc.nasa.gov/galleries/2016/lunar_transit and a total eclipse from last year https://epic.gsfc.nasa.gov/galleries/2016/solar_eclipse https://epic.gsfc.nasa.gov/galleries/2016/solar_eclipse
- jessaustin 9y ago
  I'm sure we don't have the technology to do this today, nor will we have it this century, but if TFA is ever practical then the weaponization thereof will be soon after. At that point artificial-light agriculture will probably be less expensive than today, but still more expensive than the outdoor kind.
  - tempestn 9y ago
    How would you aim the shadow? It's not a matter of technology; it's not physically possible to pinpoint a shadow from that distance.
    - 9y ago

xitrium 9y ago

What idiot called this "Feasibility of cooling the Earth with a cloud of small spacecraft near the inner Lagrange point" instead of "Solar Eclipses As A Service?"

SoMisanthrope 9y ago
LOL well played bro!

deft 9y ago

Why not a giant magnifying glass to concentrate the sun and increase temps on enemy territory?

bmcusick 9y ago

If you're going to put 20 million tons of perfectly identical gram-sized craft into orbit somewhere, it seems a lot more sensible to launch a factory to the Moon rather than launch all that mass from Earth. The CO2 added to the atmosphere from burning 2 billion tons of rocket fuel cannot be negligible.

ef4 9y ago
When you build them on earth, you aren't using "a factory", you're using a supply chain with thousands of factories and millions of people. A factory that can go from regolith all the way to spacecraft is still very speculative. As for 2 billion tons of rocket fuel, it's not trivial but it's something less than 5% of one year's current CO2 emissions, and we're talking about spreading it out over a couple decades.
sp332 9y ago
This is addressed in the paper. It's even addressed in the abstract of the paper. Edit: Second is a concept aimed at reducing transportation cost to $50/kg by using electromagnetic acceleration to escape Earth's gravity, followed by ion propulsion. The paper says that if there are rockets involved, they will be used outside of the atmosphere.
- robotresearcher 9y ago
  > It's even addressed in the abstract of the paper. Where? edit: located below (italics added) thanks. The environmental costs of launch are considered. I can't see the environmental impact of manufacture considered explicitly, though. Abstract: If it were to become apparent that dangerous changes in global climate were inevitable, despite greenhouse gas controls, active methods to cool the Earth on an emergency basis might be desirable. The concept considered here is to block 1.8% of the solar flux with a space sunshade orbited near the inner Lagrange point (L1), in-line between the Earth and sun. Following the work of J. Early [Early, JT (1989) J Br Interplanet Soc 42:567–569], transparent material would be used to deflect the sunlight, rather than to absorb it, to minimize the shift in balance out from L1 caused by radiation pressure. Three advances aimed at practical implementation are presented. First is an optical design for a very thin refractive screen with low reflectivity, leading to a total sunshade mass of ≈20 million tons. Second is a concept aimed at reducing transportation cost to $50/kg by using electromagnetic acceleration to escape Earth's gravity, followed by ion propulsion. Third is an implementation of the sunshade as a cloud of many spacecraft, autonomously stabilized by modulating solar radiation pressure. These meter-sized “flyers” would be assembled completely before launch, avoiding any need for construction or unfolding in space. They would weigh a gram each, be launched in stacks of 800,000, and remain for a projected lifetime of 50 years within a 100,000-km-long cloud. The concept builds on existing technologies. It seems feasible that it could be developed and deployed in ≈25 years at a cost of a few trillion dollars, <0.5% of world gross domestic product (GDP) over that time.

barneygumble742 9y ago

Isn't this what Mr. Burns did on The Simpsons except for Springfield instead of Earth?

SoMisanthrope 9y ago

The earth doesn't need cooling. It's been cooling since the 1800's https://realclimatescience.com/2017/08/new-video-getting-started-with-unhiding-the-decline/ https://realclimatescience.com/2017/08/new-video-getting-sta... This project would be a tragic waste of resources that could better be used to accelerate research into safer nuclear reactors.

njarboe 9y ago

$50/kg to Earth orbit would be fantastic. One could get to a much higher exit point than the 5.5 km elevation (18,000 feet) they propose for even more efficient system. Seems like a great mega-project for China. They have the resources, drive, ambition, tech, and access to many 8 km+ mountains to build a launch tower on. Hopefully this would spur the US to partner with Chile and/or Argentina to build one on one of the ~7km peaks in South America. Denali is probably out of the question, but as military project, maybe it could be done.

KGIII 9y ago
Umm... I'm not sure it is politically feasible to build a rocket launching facility on Denali. That is gonna make a whole lot of people angry. You should see what happened when they put wind turbines on the much smaller mountains of Maine. Sort of related, I happen to like the looks with said turbines. There are still untainted vistas.
- NegativeK 9y ago
  Is Denali worth it, given its remoteness, horrid weather patterns, and distance from the equator?
  - KGIII 9y ago
    From the little I know about rocket surgery, probably not. There are better places to launch from.
    - njarboe 9y ago
      From US soil? Not sure the US would put 10's to 100's of billions into a launcher and not have it in the US. Maybe the Panama Canal land grab route would be what would happen instead of Denali.
      - KGIII 9y ago
        We'd probably use the current facilities. I suppose we could also try for Hawaii or Puerto Rico. The land grab is also an option, given the likely political climate if it reaches this point. My understanding is that closer to the equator is better, with some caveats.

kazinator 9y ago

With regard to stability, just use L4 and L5! Park some anchor objects at L4 and L5, and stretch a big tape-like net between those things, in the middle of which is the shading device. Problem solved! :)

xbryanx 9y ago

The American Geophysical Union is looking for feedback from its members on geo-engineering efforts like this right now. The draft statement is a good read: https://sciencepolicy.agu.org/comment-geoengineering/ https://sciencepolicy.agu.org/comment-geoengineering/

filleokus 9y ago

Can somebody who understands the subject (or have read the paper more carefully than me) say how the moment of the shadow on the earth would be? Would it be fixed on a part of the earth or move, and if it moves, how fast and in what "orbit". I.e, would some part of the earth get more (much more?) cloudy days if this would to be implemented?

mabbo 9y ago
You wouldn't see the shadows individually. The sun would just be a little bit (1.8%) less bright.
ramidarigaz 9y ago
The inner Lagrange point is always between the sun and the earth (by definition), so the "shadow" would always be centered on local "noon" and would pass the each longitude at the same time every day.
- civilian 9y ago
  But the sun isn't a single point, it is big! In the same way that a pencil can have a sharp shadow but an office building will have a blurry shadow, the satellites would produce blurry shadows. I'm not sure of the dimensions of the inner Lagrange point-- I agree that the shadow would be centered on astronomical noon, but I think it would be so blurry, and have such a wide blur radius, as to be unnoticeable except as a change in absolute light.

mabbo 9y ago

It's also been speculated that the same idea could be used to have the opposite effect on Mars. A cloud of small satellites trying to push more sunlight towards the planet, thereby heating it up. It's all space-nerd talk for the moment, but none of the technology needed to achieve these goals is very far from reach today.

antisthenes 9y ago
In that case, neither is fusion, which is essentially free energy forever. It opens up the avenue for many more warming and CO2 mitigation techniques that are a reality today (e.g. desalination on a global scale and massive reforestation of Africa and the Amazon) As well as the ability to stop burning fossil fuels much quicker than transitioning to solar/wind.
- eloff 9y ago
  It's interesting how you think it's possible to do massive reforestation in Brazil and Africa. Think about massive reforestation of Europe or the eastern USA and I think you'll see the fundamental problem with it. That land has already been put to other use (mostly agricultural use) and cannot simply be reforested. The government would have to repurchase the land from each individual land owner to do that which is not at all practical.
  - CPUstring 9y ago
    To be fair, France currently has more forests than it did a century ago.

redthrowaway 9y ago

So what happens if a big volcano goes off and we suddenly need that sunlight again? Not too easy to clear debris out of a Lagrange point.

phkahler 9y ago

This is a shit test.

andai 9y ago
It might be! lifeisstillgood 16 hours ago I remember a quote from a US geo-engineer to the effect of "half of my job is not to come up with geo-engineering solutions that will be used, but to show people that plan B is soooo extreme that they start taking plan A much more seriously" Citation needed I know but it has stuck with me

drc0 9y ago

simpsons did it https://metrouk2.files.wordpress.com/2011/03/article-1300967207614-0b51086100000578-330784_636x336.jpg https://metrouk2.files.wordpress.com/2011/03/article-1300967...

philipkglass 9y ago

If it were to become apparent that dangerous changes in global climate were inevitable, despite greenhouse gas controls, active methods to cool the Earth on an emergency basis might be desirable. ... It seems feasible that it could be developed and deployed in ≈25 years at a cost of a few trillion dollars, <0.5% of world gross domestic product (GDP) over that time. The "few trillion dollars" part is a problem. Not because it represents a particularly high cost scheme for neutralizing the warming part of AGW, but because it's so all-or-nothing. If you invest "only" $10 billion in this scheme the marginal abatement effects are going to be pretty close to zero, because so much of the cost is front-loaded into enabling technologies that will eventually deliver direct benefits. I refer the interested reader to the classic The Political Economy of Very Large Space Projects: http://www.jetpress.org/volume4/space.htm http://www.jetpress.org/volume4/space.htm With minor adjustments, it could be generalized as The Political Economy of Very Large Projects.

digi_owl 9y ago
In other words we are fucked because of incessant shorttermism...
kanzure 9y ago
> The "few trillion dollars" part is a problem. I am not particularly convinced that this requires a few trillion dollars. Is there some hard evidence that sunshades are impossible to deploy with less than $10 billion? http://diyhpl.us/~bryan/papers2/space/Self-deployed%20extremely%20large%20low%20mass%20space%20structures%20-%202007.pdf http://diyhpl.us/~bryan/papers2/space/Self-deployed%20extrem...

drawkbox 9y ago

Deflecting sunlight in orbit is interesting. Regarding deflecting light, for a long time white roofs have been pushed as a reflection mechanism[1] to deflect and lower energy costs thus reducing emissions. Though white roofs may actually increase warning in the way it reflects light onto other particles and doesn't help block it from coming into the atmosphere. Solar roofs capture it better and may be a better emissions lowering tool. Seems like a better idea to do it from space, unless of course it goes too far and is difficult to control. [1] https://www.theguardian.com/environment/2011/oct/27/white-roofs-global-warming https://www.theguardian.com/environment/2011/oct/27/white-ro...

wellboy 9y ago
This seems really viable. Deflecting is still better than absorbing on the roof top, since roof top means 100% warmth absorption and deflection always less than 100%, probably only a fraction of that.
- sliken 9y ago
  Your assuming that the atmosphere is more transparent to infrared (from a hot roof) then optical ranges (from a white roof).
  - jwilk 9y ago
    No? The atmosphere is more transparent to sunlight than to IR, thanks to greenhouse gases. That's why absorbent roofs heat the Earth more than reflective roofs.
  - wellboy 9y ago
    No. As an a example, I'm assuming that hot roofs absorb 70% of the incoming energy and reflect 30%, where reflectig roofs absorb 10% and reflect 90%. These numbers can be a bit different, but I'm pretty sure that hot roofs absorb a multiple of energy compared to reflecting roofs. Makes sense?

hughes 9y ago

> there is no fundamental reason why launch from Earth by linear acceleration to escape velocity of 11.2 km/sec should not be possible ok... even if you build it 5km in the sky, a 1km long launch rail would still apply 6,000 Gs of acceleration. Good luck designing a spacecraft that can survive that.

sliken 9y ago
Or don't waste 5km and make the tube 5km. The acceleration drops to 1282G. Digging a 1km hole drops it to 1000G or so. Not really that much. About the acceleration a woodpecker head gets, less than a baseball being hit by a bat, or what a wrist watch can withstand. Under 1/10th that of the electronics in an artillery shell.

mchannon 9y ago

This strategy, to get rid of some sunlight, doesn't fix our problem with CO2. In fact, it's likely to make the problem worse. Our planet has two primary natural methods for lowering atmospheric CO2. One, natural weathering, is not impacted with this strategy. The other, plantlife, is absolutely affected. If you were to take 10% of sunlight away from Earth, then it logically follows that plants would get 10% less sunlight to convert CO2 into starches and H2O into oxygen. The resource you're trying to constrain, in the name of fighting effects of rising CO2 levels, is the very resource you need in order to fight rising CO2 levels. Sure, blocking or deflecting some light might lower Earth's temperatures temporarily, but you'd exacerbate CO2 levels semi-permanently. We, as a community, need to come to the realization that our CO2 problem is not strictly a temperature problem.

taberiand 9y ago
There isn't going to be one single solution, but reducing incoming sunlight by a small percentage (1-2%) could be a cost effective part of a multi-layer approach.
koverstreet 9y ago
Amount of sunlight is not the limiting factor on plant growth in most places. In fact, it's often the opposite - plants shut down respiration during midday to limit water loss because it's too hot.
- mchannon 9y ago
  I imagine "most places" refers to most places on land, which is less than 20% of the range of where plants grow. Ocean-based plantlife is the workhorse on this planet, and I would argue that the lion's share is absolutely constrained by available sunlight. Further, there's a substantial difference between "respiration" and absorption of sunlight. Pineapple plants, for instance, only "breathe" at night.
  - tlb 9y ago
    Plant life in the oceans is mainly limited by minerals, especially iron. That's why the oceans aren't green and slimy. Dumping iron powder in will usually cause an algae bloom, which eventually die and take the carbon they fixed to the bottom, so seeding the oceans with iron is a potential way of reducing CO2 in the atmosphere. Of course, like any large-scale meddling, there will be collateral damage.

gdubs 9y ago

I'm all for exploring solutions, but I also wonder about the behavioral economics at play when people "feel" like a geo-engineering solution is inevitable. In other words, how much does believing we will inevitably engineer our way out of the problem keep us from making the hard choices that may be necessary.

svachalek 9y ago
Who is the "us" that needs to make hard choices? Those that are seriously impacted by climate change and those that stand to benefit from the status quo are very disjoint sets, and the latter have shown quite an aptitude for persuading the former not to worry about it. The time for making those hard choices is quickly passing by without any significant motion. It's not time to give up yet but it's also not a good idea to just assume people are going to come around on this.
fleitz 9y ago
All solutions are geo-engineering... Exactly what kind of solution are all the things that are recommended to do to lower global CO2? The only difference is the current recommendations are inefficient and take a long time.
- andai 9y ago
  And are at odds with greed / desire for comfort and luxury.
  - fleitz 9y ago
    Exactly, which is why the whole thing is stupid and isn't going to happen. Enviros: You can enjoy longer summers and shorter winters, or you can be poor. Sane people: Longer summers and shorter winters sounds pretty good to me.

deleted 9y ago

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alkonaut 9y ago

Wouldn't earth based reflection be a lot simpler? E.g artificial clouds/ice/etc to reflect sunlight off the planet?

bigbugbag 9y ago
Like polar ice ? this would be simpler for sure but it would require very difficult things to attain such as having people relinquish their air conditioning, stopping capitalism and consumerism, changing the global industrial process, diminishing our energy consumption, replacing the current political systems with democratic ones, returning to ways of producing food that do not cause soil infertility.
- alkonaut 9y ago
  Exactly like polar ice. The problem as you point out is that polar ice is reducing which just makes it worse. And obviously this whole discussion about technological solutions is due to the fact that all those things you list seem to be impossible or happening too slowly. I doubt artificial ice is the easiest solution, but e.g artificial clouds could be perhaps.
  - andai 9y ago
    I saw something on TV a few years ago about a project to make boats which would spray a fine mist high into the atmosphere, ie. create artificial clouds to reduce the heating of the earth.
lagadu 9y ago
That's what stratospheric sulfate aerosols[0] are. Same stuff the industry already dumps into the atmosphere but dumped way higher in low amounts and easy to reverse: you can just shut it down and the effects fade over the course of the following year. [0] https://en.wikipedia.org/wiki/Stratospheric_aerosol_injection_(climate_engineering) https://en.wikipedia.org/wiki/Stratospheric_aerosol_injectio...

lifeisstillgood 9y ago

I remember a quote from a US geo-engineer to the effect of "half of my job is not to come up with geo-engineering solutions that will be used, but to show people that plan B is soooo extreme that they start taking plan A much more seriously" Citation needed I know but it has stuck with me

gene-h 9y ago

This project requires millions of square kilometers of high tech satellites. If we could make millions of square kilometers of high tech satellites then we could probably make millions of square kilometers of solar panels here on earth, and not put CO2 into the atmosphere in the first place.

andai 9y ago
"The future is already here — it's just not very evenly distributed." William Gibson The space based sunglasses would shield the entire earth. I think it would be more difficult to get millions of square kilometers of solar panels evenly distributed.

whataretensors 9y ago

Does anyone have links to a good recent research paper on climate change? With modeling details and dataset. I've looked around but it's difficult to find the best/most recent knowledge.

anotherbrownguy 9y ago

I don't understand why people are still obsessed with "global warming". The political proponents of it have already changed it to "climate change" after global temperature stopped rising for a decade and it's been almost two decades now. I would be much worried about "global cooling" i.e. another ice age. A couple of degree increase over the next hundred years (which is their worst case estimate based on the most advanced models, even though no model has been able to predict anything, only fit historical data) will change nothing. Sea levels will probably rise by a few feet and people living in their beach houses will have to find another vacation spot in 20 years after they notice that the sea has been coming closer to their house since the last decade. Ice age is just as unpredictable (except they don't even have a make-believe explanation for it) and could start any time giving us very little time to prepare. If we want humans to suffer less because of it, the least we should do is try to give over a billion people who have no access to electricity some way to make sure that they will be able to heat their houses if it's cold, like most of the developed world can... in addition, meanwhile, they can enjoy clean drinking water, washing machines, industries etc.

wellboy 9y ago
Many U.S. coast cities will become submerged when sea-levels rise by several feet. This is not the omly effect, particularly countries in the middle east will dry out, leading rural inhabitants to gravitate towards in excess of their capacities, leading to destabilised countries. This has already happened with Syria and millions if refugees, now wait for the remaining countries to follow with hundreds of millions of refugees in the next 100 years. Naturally, even heavier hurricanes, more devastating floods will happen. Keep in mind, a rise of only 6 degress fahrenheit, means a rise of 20 degrees fahrenheit in some areas and less in others. This is catastrophic for the areas that are among the ones with bad luck and will induce mass migration/fleeing.
citizen13384 9y ago
Source?
tempestn 9y ago
Most of your assertions here are incorrect. You don't need a particularly complex model to show that if more energy is absorbed by the earth than is radiated, which is the case due to greenhouse gasses in the atmosphere, the temperature will rise until it returns to a steady state at a higher temperature. This means that even if CO2 emissions stop immediately (which obviously they won't), the temperature will continue rising for a period of time (some decades). A 2 degree rise is considered to be the absolute limit without likely catastrophic consequences. It is certainly not the worst case. Sea levels could certainly rise by more than you claim, but sea level rise is far from the only problem. See here for instance: http://nymag.com/daily/intelligencer/2017/07/climate-change-earth-too-hot-for-humans.html http://nymag.com/daily/intelligencer/2017/07/climate-change-... If you're being honest about your introduction, that you don't understand why people are concerned about climate change, then that's a start. If you're instead trying to convince people of your point of view, please provide evidence for your assertions.

amelius 9y ago

Don't we need the photons to convert CO2 back into O2 through photosynthesis?

civilian 9y ago

> 3 trillion dollars This is why we need a space elevator! Costs would be reduced from $40k / kg to ~$400/kg. I spoke to an engineer at a space-focused company about space elevators. He, unfortunately, burst my bubble. While the elevator itself might be feasible, he thinks that countries would never let an asteroid large enough to act as a counterweight, with thrusters large enough to move it attached, enter Earth's orbit. The potential of it being used as a catastrophic weapon is just too dangerous.

XR0CSWV3h3kZWg 9y ago
We'd also need to advance material science and logistics quite a bit. It sounds like carbon fiber has the tensile strength, but we can't make it in near the length nor quality we'd need for a space elevator. The elevator would need to avoid or divert space junk. And we haven't actually practiced asteroid capture, much less orbit keeping on a scale that large.

nickt 9y ago

Sunstorm [1] by Arthur C. Clarke & Stephen Baxter, obliquely touches on this though with added aliens and a larger threat from the sun. [1] https://www.goodreads.com/book/show/35815.Sunstorm https://www.goodreads.com/book/show/35815.Sunstorm

godshatter 9y ago

I'm not against geo-engineering as a general concept, even though I don't personally buy into the most alarmist of the climate change scenarios. If we do do some kind of project like this, I would want to have a counter in place in case it does more harm than good, as a general rule of thumb. I would want that factored into the cost and preparations in place for just such an eventuality before committing to such a course. In this case, though, it seems relatively trivial - it seems like it's more work to keep them in place then to have them scatter to the (solar?) winds. Once they've moved out of the Lagrange point, then they become a non-issue. All we've lost is the money to put them there and the materials. Compared to some of the other ideas I've heard, this appears to be much safer.

xhasid 9y ago

Would it possible to aim to have these satellites shade only one or both of the poles? That could solve the problem of reduced sunlight for plants. (Among other issues.)

tempestn 9y ago
ISTM it would be difficult since the sun isn't a point source. Fortunately, as other comments have mentioned, sunlight is not the limiting factor for plant growth in most situations.

StefanKovachev 9y ago

YOU ARE SUCH AN IDIOTS! ... BLAH BLAH. IM ANGRY HOW SUCH AN INTELLIGENT PEOPLE CAN RATE THIS CURRENTLY IMPOSSIBLE IDEA! THE MAIN POINT IS THAT YOU NEED TO STOP THE SAME AMOUNT OF SUN ENERGY... HOW?! BULLSHIT! IDIOTS!...

SCAQTony 9y ago

How would a "cloud" at the Lagrange point be removed in the event of a global cool down or "black swan" event occurred?

throwaway7645 9y ago
My first thought as well.
cookingrobot 9y ago
From the article, the L1 Lagrange point isn't stable, it's a saddle. In the plan described here, the craft would be actively controlled to adjust how much light they're diverting and at what angle in order to stay balanced at the Lagrange. If the steering system is turned off all the reflectors would harmlessly blow away.

spenrose 9y ago

"They would weigh a gram each, be launched in stacks of 800,000, and remain for a projected lifetime of 50 years within a 100,000-km-long cloud. The concept builds on existing technologies. It seems feasible that it could be developed and deployed in ≈25 years at a cost of a few trillion dollars, <0.5% of world gross domestic product (GDP) over that time." Oh FFS. If we have a few $trillion to devote to global warming, we can enormously reduce it using known technologies. There is an important clue in this spectacular self-own to the emotional allegiances of the people who get excited about ideas such as this one.

devrandomguy 9y ago
If I was given a few $trillion to solve atmospheric CO2/CH4, I would move mining to the moon, and move manufacturing and agriculture into orbit. Then smother the Earth-side economy with cheap/free stuff to discourage the remaining entrenched industry, and offer habitat space to anyone who prefers doing physical work for a living, over living in a highly regulated paradise on UBI + patreon. For perspective, Gerard K. O'Neil gave a ballpark estimate of $31B (correction: $31B in 1972 dollars, $172B in 2013 dollars) for a v1 O'Neil cylinder made of steel. http://www.nss.org/settlement/physicstoday.htm http://www.nss.org/settlement/physicstoday.htm
sliken 9y ago
How about just invest in a solar powered way to make something useful from CO2 in the atmosphere. Like say a brick. We could make roads and buildings out of it.
- andai 9y ago
  I think trees stole your idea about 400 million years ago.
  - sand500 9y ago
    Yep, look up carbon sequestration.

AlexCoventry 9y ago

If the authors are around, you're missing some backslashes before your dollar signs, here: http://www.pnas.org/content/103/46/17184.full#sec-3 http://www.pnas.org/content/103/46/17184.full#sec-3

patrickdavey 9y ago

I'd argue that the more energy you use, the more comfortable your life is. I'd also argue that energy use (at the moment) is pretty linked to how much CO2 you emit. A lot of the biggest emitters live in democracies. So, how do you get the majority of the population to vote in politicians who are going to make their lives less comfortable (by taxing / controlling / lessening the amount of CO2 they use)? Frankly I reckon we, as a civilization, are going to dither and procrastinate up until the point it's far far far too late to do anything meaningful, and then people will try jump on the geoengineering to hack things into place. There was a nice piece in the book "This changes everything" where they were talking about geoengineering. I'll paraphrase, but basically someone said "we'll just alter things in this way", and someone else said "that'll mean droughts in my country". Fun times ahead. If you haven't read it yet, I recommend "Sustainable Energy Without the Hot Air" [0] to get an idea of just how much less energy we need to use if we want to get by with just renewables. I really hope we can get there! [0] https://www.withouthotair.com/ https://www.withouthotair.com/

mishkovski 9y ago

One option is to find a way to decrease human population voluntarily. That will reverse human related climate change in more natural and comprehensive way.

deleted 9y ago
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SubiculumCode 9y ago

Any form of geoengineering that is outside of earth mskes me nervous. Removing or altering its effect might be precluded if society breaks down (e.g.after a nucleur war)

aurora- 9y ago

Well, this could give a good reason to build a Moon base. Instead of launching all that mass from the Earth (~20 million tons), the sunshade satellites could be launched from the Moon, using an electromagnetic launcher, for just a few dollars per kg. Building a Lunar base would start with seed factories, that would then build the base, which would make the launcher and the sunshades. The amount of material needed to start the seed factories should be under 20,000 tons, or 0.1% of the mass needed to launch the sun shades directly from Earth.

Nomentatus 9y ago

"A major technical hurdle to be overcome is the instability of the orbit, which is at a saddle point." Tether from the lunar surface, through the Lagrange point.