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Lower Thermal Radiation Input Needed To Trigger Planetary 'Runaway Greenhouse'
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.
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?
so long as we aren't responsible for it?
Sheesh, evil *and* a jerk. -- Jade
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.
She was like chocolate when she drank... semi-sweet at first and then increasingly bitter.
Well, until someone comes along and terraforms it back using a sunshade.
I think at sunshade at Sun-Venus Lagrange Point 1 would do the trick.
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 power, use thin film PV instead of mylar. For cosmic ray deflection, use the power generated to drive a large electromagnet, and incorporate the ambient plasma from the sun into the design to inflate the field.)
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.
If you reply, do so only to what I explicitly wrote. If I didn't write it, don't assume or infer it.
Send it to Mars, I hear they're short on air over there.
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 dogs living together and all that.
Quite an experience to live in fear, isn't it? That's what it is to be a slave.
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.
Who says you have to live on the surface?
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!
If you could cool the planet, the atmosphere would condense to liquid except for the lighter gases.
The two are not linked. If we move off fossil fuels, our net CO2 emissions are cut to virtually zero, regardless of population (in fact, increased population acts as a carbon sink) or energy usage. Given enough cheap, carbon-free energy to distill seawater and power hydroponic stacks, we can support a far larger population if required.
Then all we have to worry about is excess waste heat, which will be a huge problem in 300-400 years. Though limiting ourselves to solar-derived energy can help a lot here.
Why would anyone engrave "Elbereth"?
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.) 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 grapes"
You have to wait for the atmosphere to literally start to freeze for venus.
Earth says: "I didn't leave the habitable zone. The habitable zone left me!"
If you think I voted for Trump because of this post, you're wrong. I voted for Dr. Jill Stein of the Green Party. Again.
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.)
Actually, steam should glow spectacularly in the far IR spectrum.
Clearly, you are unfamiliar with blackbody radiation, and with what the primary absorption/emission bands are for water vapor.
Imperial unit have no business in science, and I live in the US.
Gravity
Work Safe Porn
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
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 high pressures.
On Venus at 1 bar pressure, the temperature is actually not that far off of Earth http://www.datasync.com/~rsf1/vel/1918vpt.htm - (about 50 C = 122 F), hot, but not unmanageable if we could somehow put a floating colony there. You would have to seal the habitation anyway because the atmosphere is about 95% CO2.
I can try to explain why. So far only known life form is our carbon based, situated exclusively on planet Earth - it includes every living organism on Earth, from amoeba to whale. We do not know it for sure, but it is possible (but unlikely) that it is the only life form existing in the universe. More likely is that life is like a sparkle in time in space - that there were (insert arbitrary large number) of life forms before us, and will be even more after us, but on cosmic time scale life expectancy of average life form is very small, so most of time/space is kinda lifeless and boring, and, most important of all, lacks an observer.
It's easy to think about observer as about god - it's something that everybody have or it lives inside everybody who's alive, it does not include any part of personality, it does not have any properties at all - so everybody have the same observer, or, you can say, it's one for everybody. If you think about it this way - it does not die after your death, so it makes you almost immortal - if you define 'me' such it does not include your personality, which I believe is right - as personality is just a sum of your genes and previous life experience.
So, what can be our purpose in life, and what can be the purpose of a humane race? Based on above I believe it should be protecting and expanding areal of carbon based life form. This runaway greenhouse scenario will end up with earth without liquid water on a surface - it can possible kill all life as we know it, so we should try to prevent it, even if it will happen after our personal deaths. Anyway, on a long enough time line, chances of survival of life on planet Earth drops to zero - so I believe we should do what we can to extend life, not necessary humans - maybe just a seeds from which evolution can begin - to as many planets as we can.
CO2 alarmists pointing to Venus as a warning seem to forget that it is much closer to that big furnace, and that its composition, among other parameters, is widely different.
Fearing that earth could shortly turn into Venus is as silly as fearing that it would become a second Jupiter.
It doesn't have to be that scenario to be a big problem. just the melting of all the ice on earth alone would be a 70 meter problem.
Yes, I'm left. You have a problem with that?
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 shows how the earth was formed and also gives the current leading theory on how the water got here (and on venus and mars) -- that is that as jupiter and saturn were finding a stable orbit around the sun they caused many far out icy asteroids to come in a collision course with the inner planet in a bombardment that carried water to the surface of these planets.
So we would need to speed up the rotation of venus or smack it with big highly magnetic rocks from space to simulate a magnetic field, as well as causing icy asteroids to smash into it to make up for the lost water before we could try fun things like GM bacteria that eat sulphur. Any light compound in the atmosphere would be stripped away from a coronal outburst of solar activity and wouldn't last that 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 the net molar mass difference is about 14. Compare that to hydrogen with a molar mass of 2, which puts it's mass difference on Earth at about 28. So to get the same lift your N2/O2 blimp on Venus would need to have twice the volume as a hydrogen blimp on Earth. On the other hand a hydrogen blimp on Venus would have a molar mass difference of 42, so it would be able to carry 50% more weight than on Earth (or could be 33% smaller if you prefer), and with a CO2 atmosphere the fire risk would be virtually eliminated.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
Plus... it's nice to eradicate the human race anyway - there are just too many such vermins on this planet anyway
You go first. The rest of us could do with fewer of you self-loathing, emo douchebags.
Me? I don't give 2 shits about "the planet" aside from its use as a suitable habitat for human life. I also don't' give a crap about other life, except for its function in maintaining a suitable ecosystem for humans to thrive in.
In short, if you eradicate humans, would the planet be better off? The correct answer to this question is "Who gives a fuck?"
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.
It's all a big conspiracy, right?
I do not want your cheap brainburning drugs. They are useless for work. And I am a working man today.