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Lower Thermal Radiation Input Needed To Trigger Planetary 'Runaway Greenhouse' 137

Posted by Unknown Lamer from the poor-venus dept.
vinces99 writes with this excerpt from the UW news service: "It might be easier than previously thought for a planet to overheat into the scorchingly uninhabitable 'runaway greenhouse' stage, according to new research (abstract, article paywalled) by astronomers at the University of Washington and the University of Victoria. In the runaway greenhouse stage, a planet absorbs more solar energy than it can give off to retain equilibrium. As a result, the world overheats, boiling its oceans and filling its atmosphere with steam, which leaves the planet glowing-hot and forever uninhabitable, as Venus is now. One estimate of the inner edge of a star's 'habitable zone' is where the runaway greenhouse process begins. The habitable zone is that ring of space around a star that's just right for water to remain in liquid form on an orbiting rocky planet's surface, thus giving life a chance. Revisiting this classic planetary science scenario with new computer modeling, the astronomers found a lower thermal radiation threshold for the runaway greenhouse process, meaning that stage may be easier to initiate." If correct, the habitable zone shrinks a bit and a few exoplanets might lose their potentially habitable status. And the Earth will leave the habitable zone in a billion and a half or so years as the Sun gets brighter.
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Lower Thermal Radiation Input Needed To Trigger Planetary 'Runaway Greenhouse' More

Lower Thermal Radiation Input Needed To Trigger Planetary 'Runaway Greenhouse'

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  • Just think, both of those planets someday could have been very similar to our Earth.

    They are our sister planets, each expressing an ultimate degree to which things can go, and with what we've been discovering recently, remarkably little 'input'.

    • Re:Mars and Venus are warnings (Score:4, Insightful)

      by Maxo-Texas ( 864189 ) on Monday July 29, 2013 @06:53PM (#44418389)

      I think mars was doomed from the beginning but I wonder if Venus could be terraformed with some kind of aerosol cloud to shade it and reduce the thermal input.

      • Re: (Score:3)

        by mbone ( 558574 )

        I think at sunshade at Sun-Venus Lagrange Point 1 would do the trick.

        • You do understand, don't you, that except for the L4 and L5 points all of the Lagrange points are very unstable? If nothing else, Mercury would provide enough perturbation to move something like that out of alignment. You'd need lots of reaction mass, and frequent refueling to keep anything that big in place.

          • Re: (Score:2)

            by sFurbo ( 1361249 )
            Would the manipulating the light pressure be enough?

            I assume that the shade cannot simply absorb or reflect the light, as the light pressure would push it towards Venus, so some kind of backwards spreading would be needed. Could changing the angular distribution of this be enough to correct for the pertubations, or is a solar sail far to weak for this to work? What if the pertubations were predictable?

            • Re: (Score:2)

              by delt0r ( 999393 )
              A light enough shade it really could be enough. In fact it sounds quite doable. If you can make it big enough. Interesting fact, satellites that are orbiting a bit further out than 1000km need to take the solar pressure on solar panels into account for fuel budgets.

          • You can't remain "stationary" at an L1, 2, or 3 point without station keeping, but you can orbit those points with minimal fuel consumption for orbital maintenance. The orbit is just considerably more complicated than the elliptical orbits we're familiar with.

          • You do understand, don't you, that except for the L4 and L5 points all of the Lagrange points are very unstable?

            You do understand don't you that once we are talking about moving sun shades to Lagrange points around other planets and terraforming, that we are speaking of energy budgets that would dwarf maintenance on keeping any such item in that Lagrange point for a substantial period of time. Sort of like taking the great American cross country family road trip to Disney World and then complaining that the cost of parking might be too much.

            • Of course I understand that. I just wanted to point out that it's not quite as easy as it sounds because you have to take station keeping into account.

      • A sufficiently large artificial satellite put at the "Venus - Sun" legrange point would put venus into a state of purpetual eclipse, would/could mechanically shade the planet from solar high velocity particles, and serve as a useful space based power station for the planet. (I am thinking something like a great big sheet of metal impregnated mylar, with a weighted rim, spread open and stabilized using centrepital force. Its orbital relationship with venus stabilized using reaction wheels. For space based po

        • Totally the thing of science fiction though. Even if you eclipsed the whole planet, it would take ages for it to cool off.

          You'd also have to get rid of all the excess atmosphere somehow so a human on the surface wouldn't be crushed like a grape.

          • Send it to Mars, I hear they're short on air over there.

          • Re: (Score:3, Interesting)

            by Charliemopps ( 1157495 )

            Who says you have to live on the surface?

            • Re: (Score:3)

              by KalvinB ( 205500 )

              Gravity

              • When the atmosphere is so dense that a pleasant nitrogen oxygen mix at is a lifting gas gravity isn't as much of a problem as you might expect. And since you're airborne you neatly get around the problems associated with Venus's very long day, and you can map/explore most of the planet just by letting the winds take you where they will. Not to mention that there are elevations with approximately 1 atmosphere of pressure and comfortable temperatures too, and if your dirigible springs a leak you have equal

                • Re: (Score:2)

                  by lxs ( 131946 )

                  When the atmosphere is so dense a nitrogen oxygen mix is VERY pleasant [wikipedia.org] but not for long.

                • Floating cities in the upper atmosphere could indeed be a possibility, if for some reason you wanted to actually live suspended in the midst of continuous violent storms above a hellish inferno waiting to crush and corrode anything that sinks too deep, rather than in a nice safe space station or something. But N2/O2 makes for a pretty lousy lift gas, even on Venus. The atmosphere is almost entirely CO2, which has a molar mas of 44 versus 28 for N2 or 32 for O2, call it 30 average for simplicity's sake, so

                  • There are advantages to being in the atmosphere though that you can't get in space. First and foremost is... the atmosphere. CO2 can be cracked for oxygen, the various acids can be broken down for water and fuel. Yes, using breathable air as a lifting gas makes your dirigible bigger, but you have to bring the air along anyway and store it someplace. If you compress it down and store it in tanks you'd then need more H2 to support that weight, may as well just use it for lift.

                    Also, I think you underestima

                    • Certainly there's potentially useful materials in the atmosphere, the question is only whether it's worthwhile to risk human lives rather than having an automated refinery send supplies up to a orbiting station - something like an airship-to-orbit or skyhook system could potentially be quite effective for such a purpose.

                      Have you ever seen an aircraft getting tossed around in a thunderstorm? Now imagine trying to build a floating city that was constantly being subjected to even more violent stresses. From w

          • Re: (Score:2, Interesting)

            by Anonymous Coward

            You'd also have to get rid of all the excess atmosphere somehow so a human on the surface wouldn't be crushed like a grape.

            Why? As temperature drops, you liquify and solidify lots of the atmosphere.

            Anyway, the project, if put into effect today, would take thousands of years to accomplish. With our 4-year-election-plans, we can't even handle global warming on our planet, never mind terraforming another!

          • Depending on how long you are willing to wait, and how aggressively you are eclipsing the planet, the sunshade will eventially do both:

            At some point, the mean surface temperature will drop to the freezing temperature of carbon dioxide, and the atmosphere will crystallize, then snow out onto the surface, reducing surface pressure.

            Again, if you have a million years or more you can spend servicing the reflector, and twiddling your thumbs. ;)

          • If you could cool the planet, the atmosphere would condense to liquid except for the lighter gases.

            • The problem is that the venusian atmosphere is mostly CO2, with some anhydrous sulfuric acid thrown in.

              At greater than 200psi, and warmer than 70F (metric users can suck it. I live in the US. I don't see you guys helpfully giving imperial units on your posts! Meh! [/silly faux bitching] instead, enjoy this helpful link. [wikipedia.org]) CO2 becomes a supercritical gas. With no meniscus, the atmosphere will still ascend very high above the surface, and be too hot to condense. Items on the surface will still be "crushed like

              • Imperial unit have no business in science, and I live in the US.

                • Can you not recognize a joke when you see one?

                  I knew "off my head" what the imperial transition zone was, since I work in aerospace, and it is useful as an industrial solvent and coolant. Much like many european posters are too lazy to be arsed to look up imperial numbers for things off the tops of their heads, I was too lazy to do the same in the inverse direction. I did however, link to an informative article on wikipedia that gives the metric values for the transition point, assuming you aren't one of t

                • SI units have no business in science, either, and I live in the US too.

          • Re: (Score:2)

            by lxs ( 131946 )

            Deep sea divers don't get crushed like a grape. They do get nitrogen in their bloodstream if they breathe regular air and the bends if they decompress too quickly.
            So we "only" have to create a helium/oxygen atmosphere and good decompression facilities in the spaceports and life on Venus can be a reality. Everyone there will talk like ducks, but that's a small price to pay for interplanetary colonization!

            • Wait a second!!

              Venutian ducks can talk??

              Actually, I didn't even know Venus had ducks.

            • Deep sea divers don't get crushed like a grape.

              The surface pressure on Venus is about 900 atmospheres. Divers would have to be at the bottom of the Mariana Trench (about 6.8 miles) to experience the same pressure which is far below what a diver can dive without a protective submersible. So, yes, they would get crushed like a grape.

              • I believe that's off by an order of magnitude: the surface pressure on Venus is about 92 bar = 92 atmospheres, equivalent to a depth of about 3000 feet, slightly less than 1000 meters. Most of the Earth's ocean is much deeper than that. I think the deepest real dive (in the ocean or a lake) is around 1600 feet (500 meters). The reason for not going deeper has nothing to do with being crushed, since the gas you're breathing is at the same pressure as the water around you. Rather it is that the gases you'

        • Comment removed based on user account deletion

          • Re:Mars and Venus are warnings (Score:5, Interesting)

            by wierd_w ( 1375923 ) on Monday July 29, 2013 @09:07PM (#44419227)

            That's why you put it "sunward" of the lagrangian point, so that it wants to fall into the sun, but is pushed out of the well by the solar wind. ;)

            (Exactly where that would be depends on the specific impulse of the solar sail effect, and the mass of the reflector. Since both are hypothetical, I can't really give specifics.)

            • Re: (Score:2)

              by delt0r ( 999393 )
              The solar wind won't push much at all. Light pressure however will be quite substantial.
            • Comment removed based on user account deletion

              • It would be. That is indisputable.

                The sun in a yellow dwarf variable star. Its solar output varies, and can be quite erratic. Its gravitational attraction would vary significantly less.

                The issue is which set of problems you want to inherit from such an installation:

                1) a constant stream of supply missions to keep the unstable L1 situated reflector on station using reaction mass propellant, spare parts for thruster ports and hose assemblies, and all the related logistics.

                2) maintaing a tightrope teetering on

        • Is there some way you could use the energy to break the CO2 and sequester the carbon?

          I'd think a bacteria would be more efficient but if that wouldn't work, you could have a "balloon" with solar cells that broke the CO2 and released O2 and periodically dropped solid carbon masses to the planet.

          • There is.

            There is a manmade plastic called "aramid", which is comprised of nitrogen, carbon, and hydrogen. It has no melting temperature, and has a thermal decomposition temperature of approxmately 500c. (Just a little under the mean surface temperature for venus.) It dissolves, but does not denaturate in strong acids.

            Should an atmospheric sulfur cycle bacterium be engineered to make use of this substance for cell walls, their little dead bodies resulting from their "natural" lifecycle would fall into the l

      • Venus already has a really effective 'shade' - the bond albedo (percentage of light from the sun it reflects) is 0.9 (90%). Compared to ~0.3 for Earth

        http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html [nasa.gov]

        Venus is so hot at the surface mostly because the atmosphere is incredibly dense at the surface (93 times earth). In geneneral, as pressure increases in a planets troposphere, so does temperature. If you go deep enough into the gas giants (even Neptune), you will find very hot temperatures, at hi

        • Another fun fact:

          Total quantity of nitrogen gas in the venusian atmosphere is comparable to total quantity of nitrogen gas in the earth's atmosphere. The Venusian atmosphere is simply MUCH denser, and the nitrogen is diluted VERY heavily with CO2.

          (Meaning, if you used a compressor and condenser on a "balloon city", you could extract the nitrogen lifting gas by compressing and freezing the CO2, and then dropping it over the side as dry ice. This assumes that the balloon city is floating at 1bar pressure elev

      • I think mars was doomed from the beginning but I wonder if Venus could be terraformed with some kind of aerosol cloud to shade it and reduce the thermal input.

        I think that an answer to that requires some background. Venus has already lost most of its water to space due to a combination of things. Atmospheric sputtering due to the small magnetic field because of slow rotation rate (thought to be caused by an early collision with a proto planet early on) continues to carry along with the solar wind away lighter molecules like water and helium. Venus being closer to the sun doesn't help it either.

        This documentary [youtube.com] shows how the earth was formed and also gives the cu

    • Based on what evidence do you say that they could be in the very narrow habitable range of all the necessary parameters? And what makes you think that they are a warning of any sort? AGW hysteria is premised on lack of understanding of the heat equation. It's biggest skeptics are physicists. It's biggest proponents are Hollywood actors and politicians. If you disagree, do tell why the heat equation doesn't apply all of a sudden. If you can't, then stop spewing bull shit.
      • "All the necessary parameters"? The "Heat Equation"?

        You can't be serious.
        • I am serious. Are you? Put up or shut up. Explain why you think the heat equation doesn't apply. Or shut the fuck up.
          • Despite the straw man you are so desperately clinging to, the "Heat Equation" describes a region far greater than those of we three planets.
            • So you admit that you have no idea what you are talking about. Good. Thought so.

              • Re: (Score:2)

                by Maritz ( 1829006 )
                Your argument consisted of appeals to authority ("physicists") and ad-homs (hollywood celebrities) and then said something about the heat equation. Not compelling or interesting. Say something with substance. Explain to us lesser creatures so that we can be blessed by your wisdom.

          • Re: (Score:1)

            by Anonymous Coward

            No, they may not be valid "warnings" but that does not affect global warming. Changing the composition of the atmosphere with gasses which have different infra-read absorbance will have an affect on surface temperature, or do you think basic physics does not apply hear? Science is specialised I would trust a quantum physicist, for example, almost as much as my grandfather(who has no such knowledge) to be able to come up with valid understanding of the climate. If you as a physicist wish to look for like-

            • Muller didn't "think that climate models were wrong". And it doesn't make any difference who sponsored his research. He correctly argued that a certain variable was not accounted for in the model. The study which you point to simply accounted for that variable (the proximity of population centers to the "actual" temperature readings). That doesn't mean he went from the "heretics" to the "believers" as your comment strongly suggests. It just shows that the hypothesis, while it might be true, is most acc

      • Re: (Score:3)

        by Maritz ( 1829006 )

        Based on what evidence do you say that they could be in the very narrow habitable range of all the necessary parameters? And what makes you think that they are a warning of any sort? AGW hysteria is premised on lack of understanding of the heat equation. It's biggest skeptics are physicists. It's biggest proponents are Hollywood actors and politicians. If you disagree, do tell why the heat equation doesn't apply all of a sudden. If you can't, then stop spewing bull shit.

        AGW skepticism is akin to Intelligent Design. It's a false 'controversy' manufactured for political reasons.

        Your dismissal of the broad consensus of relevant experts is reminiscent of mount stupid. [borgerlyst.dk]

        It's all a big conspiracy, right?

  • Needs more doomsday. (Score:4, Funny)

    by Anonymous Coward on Monday July 29, 2013 @06:48PM (#44418345)

    I don't know about the rest of you, but I found the last two lines of the summary to be quite anticlimactic. Where's the fear-mongering?

    • I don't know about the rest of you, but I found the last two lines of the summary to be quite anticlimactic. Where's the fear-mongering?

      Well, it seemed pretty terrifying to me. I'm not sure what kind of plans you've been making, but this significantly moves up my time tables. Now we'll probably have to completely abandon Earth instead of preserving any as a museum for the origin of life. Well, at least we can take the gene sequences...

      Now it'll be much more of a smash and grab to get as many resources and mechanizations manufactured from the asteroid belt before we bolt for a new star-system. All but the first few percent of the plan will have to be re-calculated! Finding a younger destination star means taking a bigger risk with its instability, or planning an additional interstellar hop to last out the rest of the 4 billion years till the Andromeda Galaxy merges with this one. I mean, of course revisions are planed and there's some uncertainty to iron out as the future nears, but now Everything is Gorked! It might just turn out to be a complete cut and run to drift the nearest nebula and suck up the frigging dust dregs!

      • Re: (Score:2)

        by TheLink ( 130905 )

        It would be terrifying if you were actually an "Immortal" who can't die and yet does not have enough power to create universes or do other things to actually enjoy Eternity.

        Being stuck on a planet for billions of years till its sun blows up is not going to be pleasant especially if you can't die and you can't escape. After that you'd probably be stuck in space for a long time - which might be even worse.

        Might be fine if you have really good Immortal friends to be stuck in the same "boat" with... Not sure ho

  • No problem... (Score:3, Insightful)

    by Black Parrot ( 19622 ) on Monday July 29, 2013 @06:52PM (#44418381)

    so long as we aren't responsible for it?

  • At least according to the abstract of the research paper (couldn't read the paper itself) if Earth is brought into the hot moist athmosphere state, that state would maintain itself. From the abstract (emphasis mine):

    Therefore, a steam atmosphere induced by such a runaway greenhouse may be a stable state for a planet receiving a similar amount of solar radiation as Earth today. Avoiding a runaway greenhouse on Earth requires that the atmosphere is subsaturated with water, and that the albedo effect of clouds exceeds their greenhouse effect. A runaway greenhouse could in theory be triggered by increased greenhouse forcing, but anthropogenic emissions are probably insufficient.

    So we will probably not manage to terraform Earth into Venus just by continuing CO2 emissions. But maybe if the Vogons [wikia.com] help a bit ....

    • We don't have enough carbon to do this.

  • Forever is a long time (Score:3)

    by mbone ( 558574 ) on Monday July 29, 2013 @07:01PM (#44418459)

    As a result, the world overheats, boiling its oceans and filling its atmosphere with steam, which leaves the planet glowing-hot and forever uninhabitable,

    Well, until someone comes along and terraforms it back using a sunshade.

  • A billion years or so should be enough for everybody.

  • This article is so affordable. Only 22 pounds. We are so privileged to have the opportunity to read this study. Just imagine a world where such study results were just given away for free. Communism!

    It really is a much better world where only paying customers have access to scientific research. It is destructive and dangerous to allow poor people access to knowledge. In that way lies anarchy! The horror. Next we'll be arguing not only that information wants to be free, but that it should be free. Cats and d

  • what about weather dynamics? (Score:4, Interesting)

    by khallow ( 566160 ) on Monday July 29, 2013 @07:22PM (#44418619)
    What puzzles me is the absence of discussion of rain storms. These transfer a lot of heat to the upper atmosphere where it is radiated to space. They also pump energy into wind, increasing the circulation of air and increasing the heat loss from those convection effects.

    Also, I gather the relative heating depends on the spectrum of the star to some degree. I gather there's some degree of transparency of water to the lower frequency UV so a bluer star with the same energy influx might have a bit more energy penetrate the atmosphere than a redder star.

  • whoa wait, it's not climate change??? (Score:1, Insightful)

    by Anonymous Coward

    "And the Earth will leave the habitable zone in a billion and a half or so years as the Sun gets brighter"

    There, you said it, has nothing whatsoever to do with "climate change" here on earth, it's all the S-U-N!!! ;)

  • I wish I could read the actual studies. Most are paywalled. Can we change this? I want to learn!

  • While this may be true, I'll take warding off the next ice age in 10,000 years if global warming is the cost. Between the two, higher sea levels is a no-brainer.

  • I think it's a , it's a , gh-gh-gh-greenhouse gas global warming monster!

    Quick you assclowns! Get into the mystery hybrid mobile! *Vrrrrooooomm*

    I think it's still chasing us! How could that be? We left the Hubbert peak way behind with our super efficiency!

    Uh-oh, if my calculations are correct, the only people our efficiency was helping was the *gulp* big oil companies themselves.

    *poof* The monster appeared in the mystery hybrid mobile! The monster tore its own mask off!

    "Will you kids shut the **** up? I'm n

  • Oh, ok, I thought it said a Million and half years. I was worried.

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