I must save the world!
May 28, 2006 12:38 PM   Subscribe

I had an idea for a temporary solution to postpone global warming crisis. Does my idea make any sence?

I've been watching the previews for Gore's movie "Inconvienent Truth" and I've been thinking of solutions for this problem.

If the melting polar caps can cause the greatest problem, can we build large light weight structures sent into orbit that can cast huge shadows on portions of the Earth? My theory is to precisely control ambient sunlight cast on the globe, thus reducing regional temperatures.

Basically a titanic sized umbrella made of an extremely durable yet lightweight material that can be launched and unfurled once in orbit. Also a structure that can be expanded upon with multiple missions.

The structure should also be equipped with a built in self destruct mech in case this umbrella idea somehow backfires.

The further out from Earth the orbital path of the umbrella, the larger the shadow.
posted by SwingingJohnson1968 to Science & Nature (54 answers total) 4 users marked this as a favorite
 
PS. This device is not a premanent solution. Just to buy us some time while we clean up our act.
posted by SwingingJohnson1968 at 12:40 PM on May 28, 2006


But wouldn't putting the earth into shadow just give you the opposite problem? It'd surely get much too cold. I think the earth's temperature is too finely balanced for something like this to work, which is why a bit of carbon dioxide can throw it out of whack in the first place.
posted by reklaw at 12:45 PM on May 28, 2006


In the first Red Dwarf book, Earth had a similar thing. It was called an ozone plug.
posted by veedubya at 12:48 PM on May 28, 2006


Wasn't there a Simpsons episode involving this? Was it the one where Mr Burns gets shot?
posted by matthewr at 12:53 PM on May 28, 2006


But wouldn't putting the earth into shadow just give you the opposite problem? It'd surely get much too cold. I think the earth's temperature is too finely balanced for something like this to work, which is why a bit of carbon dioxide can throw it out of whack in the first place.
posted by reklaw at 12:45 PM PST on May 28 [mark as best answer] [+fave] [!]


Well, my theory with this device is to create precise small shadows cast in certain regions using mathmatical equations to control the shadow/temperature ration.

The precise control of the umbrella would depend on orbital position and distance.

From what I understand, Earth temperature data can be recored with extreme accuracy and very small changes in temperatures can cause of catastrophic weather events. So maybe the giant umbrella can balance this out, temporarily.
posted by SwingingJohnson1968 at 12:54 PM on May 28, 2006


very small changes in temperatures can cause of catastrophic weather events.

This is true. So your solution to dealing with a highly chaotic system that we do not at all understand is to... supply it with unusual input data. I am not sure this is wise.
posted by atrazine at 12:59 PM on May 28, 2006


Read about global dimming, which is what you are proposing having already occured as non-CO2 solution reduces the amount of sunlight reaching the earth.

Though it may very well work, there is not going to be any megascale engineering of this sort for a long time. It is too expensive to put things into space.

There's also orbit problems - you can't really place anything in stationary orbit over anywhere but the equator, although you might not need specific or stationary positioning for your project to work.
posted by TheOnlyCoolTim at 12:59 PM on May 28, 2006


I asked a related question a while back.
posted by Galvatron at 1:02 PM on May 28, 2006


solution -> pollution
posted by TheOnlyCoolTim at 1:03 PM on May 28, 2006


In the Red/Green/Blue Mars trilogy, large mirrors are used to direct more heat at Mars to warm it up. I guess if that works, so would the reverse.
posted by Orange Goblin at 1:06 PM on May 28, 2006


Since the light from the sun is nearly collimated, it doesn't matter how far out the structure is placed; the shade-producing structure would have to be as big as the desired shadow.
posted by MrMoonPie at 1:25 PM on May 28, 2006


Note that airplane shadows are nearly the same size as the airplane, regardless of the plane's altitude.
posted by MrMoonPie at 1:26 PM on May 28, 2006 [1 favorite]


I was just watching a documentary on the global dimming issue. One of the results of global dimming was a shift in the season monsoons of sub-saharan Africa. The basic conclusion was that particles in the atmosphere resulted in the both the obstruction of light reaching the surface and in the greater reflectivity of the clouds. This prevented the tropic region of the Atlantic ocean from being heated by the sun in its normal seasonal progression which prevented the rain belt that normally provided the seasonal monsoons to sub-saharan Africa from shifting north to do so.

Long story short. The famine there in the mid-eighties that killed so many people is thought to be directly related to pollution produced by Europe and the US which increased the reflectivity of the clouds, which prevented sunlight from reaching the earth, which prevented the normal progression of the weather.

So yes it would work, a form of it is working right now, but it is also much more complex than just blocking the sun and waiting for everything to cool down.
posted by 517 at 1:30 PM on May 28, 2006


I had this EXACT idea. I was thinking about writing a funny blog entry, but my blog's down and now you've beaten me to it. I feel like it's just crazy enough to work, but then again I am just a political scientist with an overactive imagination, not a physicist.

The big downside I thought of was that it could fuck up global water currents in a way that might cause just as many problems.

But still, if we are looking at imminent doom due to icecap cycles being thrown askew, it might be worth trying to give them a little help staying cold.
posted by Embryo at 1:41 PM on May 28, 2006


A similar idea has been proposed: placing a thin, concave fresnel lens at the L1 point between the earth and the sun. (L1 -> the place where the gravatational pull from the earth and the sun balances out; fresnel lens -> found in those flat, grooved magnifying glasses)

Check it out here.
posted by Maxwell_Smart at 1:48 PM on May 28, 2006


can we build large light weight structures sent into orbit that can cast huge shadows on portions of the Earth

Consider the practicalities of this. The Earth's profile is 127731695760000 square meters-- that's how big something would need to be to completely block out the sun. Instead of putting it in orbit around the Earth, where it would only work when its orbit occulted the sun, let's say you put in orbit around the sun, with a slightly smaller orbit that the Earth. You'd need to continuously adjust its orbit to keep it in synch.

If you wanted to block 1% of the sunlight hitting the Earth, this umbrella would need to be 1277316957600 square meters. If you made it out of something that was only 10 grams per square meter, it would weight 12773169576 kilograms.

According to wikipedia, the cost of payload delivery starts around $5000/kg. To get it into solar orbit would probably be several times that.

So shipping and handling would come to at least $100,000,000,000,000, ten times the U.S. GDP. Actually building the darn thing would be a lot more.
posted by justkevin at 1:53 PM on May 28, 2006


No, your idea makes no sense, at least in practical terms.

The sun is far enough away that by the time its rays reach the earth they're close enough to parallel as to make no difference.... so in earth orbit your umbrella would have to be thousands of miles across to noticeably cool the earth. It'd be incredibly expensive to build something that size even on earth, and nigh-impossible to get it (or its raw materials) into orbit.

Trying to get a bigger shadow by putting it in a closer orbit around the sun instead of orbiting around the earth is even more implausible; even if you pretend we have the technology to do something like that, which we don't, it'd now be orbiting at a different speed than the earth, so you'd only get very intermittent shadows at best -- I'm not going to try working out the mechanics of it, but I'd guess we're talking best case a few minutes of shadow every year. Not much return on your vast investment in umbrella technology.

Not to mention that all that industrial activity involved in building it would mean pumping even more greenhouse gases into the atmosphere, making the whole problem worse than when you started.
posted by ook at 2:01 PM on May 28, 2006


What if it was anchored to the Earth, though? Like with those carbon nanotubes. You could even use a nanotube elevator to build the thing in orbit. That way, it could cover specific places, i.e. the ice caps.

The other idea I had was building it out of e-paper, which is extremely cheap per meter and could be switched from black to white easily in certain places to control absorption/reflection.
posted by Embryo at 2:02 PM on May 28, 2006


Also, a single space shuttle launch produces as much CO2 as all the cars in the US running for two minutes. Since a typical shuttle payload is only a few thousand kilograms, the pollution effect will be comparable to the entire US automotive fleet.
posted by justkevin at 2:04 PM on May 28, 2006


Hmmm, your idea seems like a simplistic approach to a complex problem. And those very seldom work. If you really want to safe the world, stop polluting it with your car (instead of putting gigantic umbrellas in space - how are you going to clean those up?) - using less oil would also force some governments in the middle east to rethink their stance on more violent issues at hand.
posted by m.openmind at 2:08 PM on May 28, 2006


This is an option in the turn-based strategy game "Sid Meier's Alpha Centauri". Typically, deploying the solar shade will cause the oceans to fall 333 meters, and there is an option to later increase the shade for an additional decrease in the sea level.

It's a pretty good idea to put this option to a vote of the planetary council as soon as rising sea levels are detected.

I've never used the "melt polar ice caps" option, but it's also available.

None of these options seems to actually cost anything, but you do have to attain a high level of technology first. We are still a few Breakthroughs away from that level here on earth.
posted by jepler at 2:09 PM on May 28, 2006 [1 favorite]


Trying again, this time with the google cache.
posted by Maxwell_Smart at 2:21 PM on May 28, 2006


A similar and simpler idea would be to cover the caps with mirrors. Much of the solar radiation would reflect back into space. Think of alllllll that area to cover, though. That's a lot of mirrors. And you wouldn't even have to get anything into orbit / maintain its orbit. You think you can launch anything that big into space and keep it all in one piece while in orbit? Mmmm. I don't think so.
posted by scarabic at 2:27 PM on May 28, 2006


Hmmm, your idea seems like a simplistic approach to a complex problem. And those very seldom work. If you really want to safe the world, stop polluting it with your car (instead of putting gigantic umbrellas in space - how are you going to clean those up?) - using less oil would also force some governments in the middle east to rethink their stance on more violent issues at hand.
posted by m.openmind at 2:08 PM PST on May 28 [mark as best answer] [+fave] [!]


Yep, I know it's a simplistic idea. That's why I posted "This device is not a permanent solution. Just to buy us some time while we clean up our act.".

Regarless of how "Simpsonesque" or "Red Dwarflike" the idea sounds, some temporary ideas need to be considered to buy us some time.
posted by SwingingJohnson1968 at 2:29 PM on May 28, 2006


Wow, I never thought I'd see one of these threads pop up on AskMe.

Temporary solutions to a permanent problem never buy time -- they simply allow people to ignore the problem for a bit longer. I have no idea what your career is, but take a look at temporary solutions to computer problems. I've put several 'temporary' servers in place that are running 5 years later. The original problem still exists, and is still going to blow up in their face someday.

You're right that it's an immediate problem, but it's going to take a very painful experience for the 90% of the world that needs to change to actually wake up and change their lifestyle.
posted by SpecialK at 2:49 PM on May 28, 2006


I don't see any reason why this wouldn't work, but I think it would cost a lot of money to do. Far more money then curbing carbon emissions.
posted by delmoi at 2:53 PM on May 28, 2006


Yes, you could do it.

You probably wouldn't want to, as it wouldn't be a very cost-effective way to deal with the problem. Probably cheaper and more effective just to freeze atmospheric CO2 into dry ice and lob that into orbit instead of the shade material.

In addition to the problems mentioned above, any shade that's big enough to work and light enough to be remotely feasible will also be a very fine solar sail and be driven away from the sun by solar wind and photon pressure. So you might well need completely laughably astronomical amounts of propellant to keep it on station.
posted by ROU_Xenophobe at 2:55 PM on May 28, 2006


Also, a single space shuttle launch produces as much CO2 as all the cars in the US running for two minutes. Since a typical shuttle payload is only a few thousand kilograms, the pollution effect will be comparable to the entire US automotive fleet.

The shuttles main engies burn liquid hydrogen and liquid oxygen, producing water vapor as the only exhaust. If we were going to do this, it would be easy to do it using hydrogen only.

But like I said, the whole thing would be more expensive then just put in the CO2 limits.
posted by delmoi at 2:57 PM on May 28, 2006


I don't see any reason why this wouldn't work, but I think it would cost a lot of money to do. Far more money then curbing carbon emissions.

Keeping things in space for prolonged periods of time is really really hard unless you boost them periodically, or put them in stupidly high orbits. Geostationary especially.

Also keeping it aligned would probably be really hard as well. There is a lot of random junk up there and the bigger you are the more likely you are to get hit by it. And as it would have to be rather light to ever get lifted, then relatively small objects would damage it and cause it to drift. You can't really keep things in a geostationary orbit at that high a latitude either.

You can't tether it anywhere but the equator, but we can't even produce the materials required to construct a tether yet on any sort of scale beyond a test tube. And that's only the beginning of the problems when it comes to tethers. Where do you tether it? How much land do you require to be evacuated and declared a no fly zone around the tether? What happens if the tether breaks?

What effect would creating random / strategically located shadows even have on the atmosphere?

So yeah, you have the short term solution that, might work, possibly, if you could construct it and get it into space before any other vaguely worth while solution became an option.

This is a great idea if you ignore all the parts where it isn't.
posted by public at 3:07 PM on May 28, 2006


In addition to the problems mentioned above, any shade that's big enough to work and light enough to be remotely feasible will also be a very fine solar sail and be driven away from the sun by solar wind and photon pressure. So you might well need completely laughably astronomical amounts of propellant to keep it on station.

Not if you make it out of plastic :P
posted by public at 3:08 PM on May 28, 2006


The shuttles main engies burn liquid hydrogen and liquid oxygen, producing water vapor as the only exhaust. If we were going to do this, it would be easy to do it using hydrogen only.

Two words: Solid Boosters
posted by SpecialK at 3:19 PM on May 28, 2006



Probably cheaper and more effective just to freeze atmospheric CO2 into dry ice and lob that into orbit instead of the shade material. ROU_Xenophobe

I do admit my giant umbrella idea is cartoonish and not practical, but at least it is provoking some other good ideas.

I'm sure there are a thousand good ideas being experimented with right now by qualified scientists.

The thing that bothers me the most is we only get 1 shot at this when used on a global scale.

So the type of theory and course of action like the one ROU_Xenophobe posted above feels the safest.

A course of action that can be perpetrated gradually and data collected. Something that has an emergency kill switch.

The question is, can we discover some element that can eat up C02 on a large scale with the control that won't strip off earth's balanced atmosphere and screw things up worse?
posted by SwingingJohnson1968 at 3:28 PM on May 28, 2006


The question is, can we discover some element that can eat up CO2 on a large scale with the control that won't strip off earth's balanced atmosphere and screw things up worse?

Trees.
posted by matthewr at 3:46 PM on May 28, 2006


For a fraction of the amount of money as building this monstrosity you could probably buy every driver in the industrialized first world a brand new turbodiesel or electric hybrid, and destroy every last remaining conventional car. This would be far cheaper and more practical than building some kind of umbrella. So I don't see why we're even considering this half-baked idea as remotely feasible.
posted by Rhomboid at 4:04 PM on May 28, 2006


Hey, don't jump all over SwingingJohnson - at least he's thinking about the problem. Half-baked ideas are great for starting discussions and inspiring more realistic approaches. They're only a problem when Halliburton gets the contract ...
posted by Quietgal at 4:45 PM on May 28, 2006


IA(almost)AGeologist. I know it seems like the world is getting out of control and we're all to blame, but the world's actually been around far, far longer than we can comprehend. 4.6 billion years, to be precise. And during those billions of years, there have been many times when the earth's been hotter than it is now, and many times when it's been cooler.

Around a hudred million years ago, the oceans were about 150 metres higher than they are now. In the last ice age, they would have been many hundreds of metres lower.

So, we've stepped onto the planet and evolved and suddenly we're here and we can understand something of what's going on around us. This has only happened in the last 500 years or so. Even the last 100 years, almost. And if you look at the earth's temperature over the last 100 years, it has definitely increased. If you look at it over the last 1000 million years, however, the temperature has stayed fairly stable within a band of maximum and minimum temperatures. At the moment, we're at a maximum. So the whole global warming thing is true, but it's not like the planet was constantly nice before we showed up, and now it's totally out of control.

Yes, we've played a part, and yes, I'm all for cleaning up our act, but trying to stop a natural cycle of the earth that's been happening for billions of years is not going to help. Cooling Antarctica, say, (and this is pure conjecture) could very easily change the ocean currents that control climate around the globe, resulting in huge catastrophic weather changes.

So I'm with Rhomboid. Use the money to produce cheap, easily manufacturable alternative fuel vehicles. Trying to 'fix' the world in such an artificial way can only make things worse.
posted by twirlypen at 4:56 PM on May 28, 2006


I'm with Rhomboid -- what if we just used the scientific R&D and construction/implementation funding to convert the entire planet to alternative energy and quit using coal-, oil- and gas-fired energy?
posted by salvia at 4:59 PM on May 28, 2006


Probably cheaper and more effective just to freeze atmospheric CO2 into dry ice and lob that into orbit instead of the shade material

Probably still insanely expensive for no benefit! Lobbing very heavy things out of the pull of earths gravity is rather expensive. Somewhere in the region of $1000 a Kg iirc. Oh which we produce millions of tons of the stuff annually. Of course you have to freeze the stuff first too. That's going to be pretty hard and energy expensive. And producing the Hydrogen and Oxygen liquid fuels as well.

Nothing about space is cheap or easy.
posted by public at 5:07 PM on May 28, 2006


Probably still insanely expensive for no benefit!

Sure. I didn't mean to imply that lobbing dry ice into space wouldn't be pointless and dumb.
posted by ROU_Xenophobe at 5:13 PM on May 28, 2006


Swinging Johnson....I think I see a major flaw.

What about all the creatures that need sunlight in that region? You're condeming them to death. The ones under the sea, that are part of the ecosystem (even at northern latitudes) that supply food upstream in the food chain. If you make your shade big enough, you may cause enough damage to cause massive problems in our ecosystem/food chain.

The problem with *simple* solutions are *simple* flaws.
posted by filmgeek at 5:38 PM on May 28, 2006


Finally, an excuse to blow up the moon. The asteroid belt will provide needed shade and a first line of defense from our alien invaders.
posted by arruns at 6:46 PM on May 28, 2006


The fundamental problem isn't even the engineering, as formidable as that would be. The hardest part is determing how much shade is enough. Too little, and we don't really accomplish anything. Too much, and we could plunge into a deep ice age.

It takes a LONG TIME for this stuff to work... even the shortest of normal climate cycles are usually hundreds of years long. By the time we realized that we were giving too much shade, it might be too late... or we might overshoot the other way again if we removed the whole thing.

It's a bit like a beginner flying an airplane...t he impulse is always to overcorrect, and the plane gets wilder and wilder and wilder... the more actively the beginner tries to exert control, the more unstable the plane gets, because he/she exerts too much force for too long.

We're a long, long way from being able to do any such thing safely.

Another thought: human goverments aren't known for lasting that long or being that stable. What if we put a shade up and proceed to nuke ourselves badly enough that we no longer have the technology to understand or adjust it?
posted by Malor at 6:59 PM on May 28, 2006


You could build the shield from oceanwater. Use a space elevator and pump a few billion gallons into orbit. You'd simultaneously be eliminating the extra water from the oceans while shielding the ice caps.
posted by exhilaration at 7:20 PM on May 28, 2006


Actually, an easier solution may be to put all our efforts into producing a working time machine.
posted by SwingingJohnson1968 at 9:14 PM on May 28, 2006


The shuttles main engies burn liquid hydrogen and liquid oxygen, producing water vapor as the only exhaust. If we were going to do this, it would be easy to do it using hydrogen only.

Yes, but the production of hydrogen produces CO or other greenhouse gases.
posted by justkevin at 9:35 PM on May 28, 2006


You can't have anything hover in orbit over the poles. This is only possible at the equator because their is a particular distance that makes one orbit around the Earth in 24 hours, so the Earth's spin and the satellite's orbit keep the Earth's surface aligned with the position of the satellite. This doesn't work at the poles because the poles don't change position, just spin in place (rotation instead of translation), so the poles can't move with the satellite.

If you want to read about intriguing approaches to countering global warming, look up research about seeding the oceans with powdered iron.

"The sun is far enough away that by the time its rays reach the earth they're close enough to parallel as to make no difference."

People say this all the time and it's so obviously false. Sun shadows include penumbras. Yes the sun is far away. It also happens to be freaking huge, I mean like really, really big. Only point sources from great distances produce effectively parallel rays. The sun only qualifies on one of those aspects. Next full moon, go out and look at it. It has discernable width and features. That alone tells you that the moon, which has the same degree-of-sky width as the sun from earth, is not casting effectively parallel rays. Imagine placing a supa-brite (tm) flashlight on nearly opposite edges of the moon, pointed at you. Because the are far enough apart in angle, they will produce PARTIALLY overlapping shadows. The same angular differences are at play in the arrival of light from the sun, from all over the visible disc it presents to us.
posted by NortonDC at 10:42 AM on May 29, 2006


"Next full moon, go out and look at it. It has discernable width and features. That alone tells you that the moon, which has the same degree-of-sky width as the sun from earth, is not casting effectively parallel rays."

That needs more clarifying. If you can discern features, that means your eye has been able to sort out the various directions from which light has been reaching it, meaning that light is arriving at the pupil of your eye from more than one direction, meaning the light reaching your eye from the moon is not parallel, but still travelling in more than one direction instead.

And I saw the "their" as soon as I hit post, and rued it.
posted by NortonDC at 10:50 AM on May 29, 2006


Well, let's find out, shall we?

Diameter of the sun is 870,000 miles (which, yeah, is fucking huge), distance from sun to earth is 93,000,000 miles. We want to calculate the greatest angle of light at a given point on earth, which will be between the rays cast by the sun's "top" and its "bottom"; we can get half of that angle by making a right triangle with sides from sun center to earth (adjacent side to the angle we want), and from sun "top" to sun center (opposite side to the angle we want), giving us tan(x) = (435,000 / 93,000,000). X comes out as .0046 degrees, doubled is about nine hundredths of a degree.

Not exactly parallel. But close enough as to make no difference, if you're talking about how it's going to affect the size of a shadow cast by something in earth orbit (geosynchronous orbit is only 22,000 miles or so.)

I have no idea what your point is about the moon; I've reread that description fifteen times and can't figure out at all what you're trying to say there.
posted by ook at 3:07 PM on May 29, 2006


Damn. I skipped a step. .0046 is the ratio; the inverse tangent is 0.26, so we're talking about half a degree difference, not nine hundredths. Which if I had looked at the wikipedia entry on collimated light, I'd have been able to skip the math.

So I stand corrected; half a degree is small, but not completely insignificant.

None of which changes what a stupid idea this umbrella is, of course. :)
posted by ook at 3:16 PM on May 29, 2006


I'm totally mystified by (but no longer surprised by) the urge to calculate a result from two derived values and multi-step trigonometry, when that value can be directly measured, namely the arcminute width of the sun from the Earth (approximately 32, by the way).

And ook, your first reponse implies that Lagrangian points may be new to you.
posted by NortonDC at 4:10 PM on May 29, 2006


So... this is a pissing match now? I used math instead of going outside and squinting at the sun with a ruler, so that's somehow... bad? Huh?
posted by ook at 7:38 PM on May 29, 2006


Huh? Not at all. I didn't even mention the sun's equatorial bulge invalidating the "top to bottom is the widest dimension of the sun's disc" assertion you made. Obviously that would have come up if we were pursuing a pissing match, instead of me acknowledging that you were being understatedly clever in letting readers think that their relative view of the sun was in accord with it's polar orientation, when really you were silently accommodating their orientation bias. That was brilliant, a fine example of leveraging the lay perspective.
posted by NortonDC at 8:05 PM on May 29, 2006


It should be noted that at least one near-arctic community is considering a space-based mirror to improve their climate by warming things up a bit. You might have competition with your umbrella...
posted by nomisxid at 4:45 PM on May 30, 2006


All you doubters are eating your words now!
posted by nathancaswell at 5:53 PM on January 29, 2007


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