(Part of the How to Talk to a Climate Skeptic guide)
Objection: The so called "Greenhouse Effect" which is the underpinning of the entire theory of anthropogenic global warming claims that greenhouse gases in the upper atmosphere absorb outgoing long-wave radiation from the surface and reradiate it back, thereby warming the climate. But the upper atmosphere is colder than the lower atmosphere and the surface and the second law of thermodynamics clearly requires that heat flow from warmer areas of a system to colder ones, the opposite direction that greenhouse theory requires. The cooler atmosphere can not radiate energy to the warmer surface. The greenhouse effect is a myth because it violates the second law of thermodynamics!
Answer:
No argument with the second law of thermodynamics here, that one seems to be on pretty solid ground! But the train of logic above has a subtle problem in its over statement of the constraints this law places on energy flow. Given a warmer and a cooler body exchanging energy either through convection or through radiation, the fact is, energy is constantly being exchanged in both directions. The second law of thermodynamics does not apply to individual molecules, it applies to the net flow of energy in the entire system. How could it be otherwise?
When an excited molecule of CO2 releases a photon, it does not somehow "know" which way to send it. It can not aim it towards a cooler body. It is simply released in a random direction. In the case of CO2 in the atmosphere, having absorbed some of the energy radiating towards space from the surface of the earth, this random choice of direction means that, roughly speaking, half of that energy is sent back. An individual molecule is not influenced at all by the temperature of the earth's surface.
Where the second law does apply is in the net flow of heat, and this happens because a warmer body will send out more energy overall than it is receiving from the cooler one. Lots of energy going back and forth, but on balance more is leaving the warmer body.
The IPCC has provided this nice graphic of what is going on. They have also used the analogies of a blanket and a garden greenhouse in their FAQ sections.
In the case of the simplified earth-atmosphere system, the Earth's surface warms from the sun's incoming shortwave radiation. As it is now a warm body floating in cold space, Earth radiates long-wave energy back out at a rate that is dependent on its temperature. If that were the whole story, the earth would have balanced its incoming shortwave with its outgoing long-wave radiation at an average surface temperature of roughly -18°C and it would be a rather inhospitable place. As it is, the content of greenhouse gases in its atmosphere absorb some of that outgoing long-wave radiation and send it back down where we all live. The earth must balance this by warming enough so that it can radiate this additional energy back out again. The totality of this natural effect is around 33°C, bringing our average surface temperature to a comfortable +15°C.
So, it is not really like a blanket, which inhibits convection in both directions, or like an actual greenhouse, which lets in the sunlight and then also inhibits convection, but both are reasonable analogies as far as they go. The scientists in the IPCC know this, they are only using these analogies to help laypeople understand the very general principles. If you hear someone attacking climate science by attacking these analogies, they are attacking a strawman.
As we have added to the greenhouse effect, the planet's surface must now warm until it reaches a new equilibrium temperature high enough to radiate out as much again as it is now receiving.
This is all very well established and long standing physics. No basic ignored mysteries, no violations of fundamental laws, just great explanations of naturally observed phenomena all over the solar system and beyond.
This is just one of dozens of responses to common climate change denial arguments, which can all be found at How to Talk to a Climate Skeptic.
"Greenhouse theory violates the laws of thermodynamics" is also posted on A Few Things Ill Considered, where additional comments can be found, and where the author, Coby Beck, is more likely to respond.
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Comments
View as Flat
Russ Posted 4:04 am
12 Sep 2008
A simpler way of saying this
(which also works vs. the anti-evolution cretins, who sometimes make a similar entropy argument), is to say that the 2nd Law applies to closed systems, while the earth is constantly receiving a massive infusion of new energy from the sun, and this overrides entropy.
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KenG Posted 4:15 am
12 Sep 2008
Applicability of Second Law
Russ, if you try that argument with someone who has actually studied thermodynamics, you're going to get laughed at. The second law is applicable to both open and closed cycles. It's usually demonstrated with closed cycles because that's much simpler. Neither the Kelvin-Planck or the Clausius statement of the second law has any restriction on the type of cycle involved.
"overrides Entropy"?? What on earth does that mean?
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Russ Posted 9:43 pm
12 Sep 2008
keng
This is not a physics seminar, but a political battleground. For those purposes, the "simpler" conception is sufficient.
Thus (from Wikipedia):
In the big scheme of things the universe is a closed system, and the sun is expending its finite energy and thus increasing entropy, and the 2nd Law is operative.
But for our purposes, our eyeblink of existence in geological, let alone solar time, we can say the sun is an infinite outside driver of what would otherwise be a closed system, the earth.
So for me the salient concepts in the above description would be: "not isolated", "not hindered", "equilibrium".
So I emphasize the "thermodynamic" rather than the "statistical" definiton. Sue me.
From the Merriam-Webster Online Dictionary:
The relevant definiton here would be 3a.
Entropy (wikipedia again):
So the sun "overriding entropy" would be its new energy input "prevailing over...the randomness of molecules" and the consequent "smoothing out differences", which would otherwise defeat the greenhouse effect.
Glad I could help.
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WWAGD?! Posted 9:49 pm
12 Sep 2008
Is The Earth Cooler from Outer Space?
Is a corollary of the Greenhouse Effect that the Earth should be cooler when seen from outer space?
That is, imagine a CO2 layer, one molecule deep, that has a density such that 5% of all infrared energy is absorbed and re-emitted (I say one molecule because I don't want to deal with it being bounced to other Co2 molecules within the layer itself).
So, an infrared ray, has a
0.05 x 1/2 = 0.025 chance re-emitted to Earth.
0.025 re-emitted to outer space.
0.95 passing right through CO2 to outer space.
0.975 total chance outer space.
Now double the density of the CO2 layer:
0.10 x 1/2 = 0.5 re-emitted to Earth.
0.5 re-emitted to outer space
0.90 pass through to outer space
0.95 total chance outer space.
So has the Earth been "cooling" when viewed from, say, the Moon?
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SamHec Posted 3:16 am
13 Sep 2008
Depends
jabailo,
It depends upon which Layer of the Earth you are looking at. The Troposphere, closest to the surface, is warming. But the Stratosphere, next layer up, is cooling a little; likely this is because less heat is transferring to the outer atmosphere due to increasing greenhouse gasses preventing as much. If the Sun's luminosity were increasing, the Stratosphere would be warmer too.
Models have predicted all this, observations confirm it. And of course, the Climate Cranks use the cooling stratosphere to argue that GW is a myth.
This is STILL not a Signiature!
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WWAGD?! Posted 4:11 am
13 Sep 2008
No, Total
No, I'm not saying look at individual layers.
I'm saying, from the Moon, the total amount of infrared allowed to escape should be decreasing as the Earth "traps" infrared according the Greehouse Effect.
So, infrared sensors on the Moon, would see a total decrease as more infrared is retained on Earth.
Are you saying that observations from the Moon or another distant location have shown the Earth as a cooler body over the 30 or 40 years of cooling? Haven't we ever sent up a satellite at a high enough orbit to measure this?
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GreyFlcn Posted 5:26 am
13 Sep 2008
Yes Bailo
The total amount of heat leaving the earth is going down.
Thats why the stratosphere is cooling.
Because there's less heat exiting through the stratosphere at any given time.
Less heat? More Cold.
http://greyfalcon.net/forcing2.png
-David Ahlport
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GreyFlcn Posted 5:27 am
13 Sep 2008
Oh yeah
And over 99% of the earth's atmosphere is represented by the troposphere, and the stratosphere.
It's basically a vacuum after the stratosphere.
-David Ahlport
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WWAGD?! Posted 8:55 am
13 Sep 2008
CO2, Tea or Heat
Seems like there'd be some optimal CO2 density at which that layer would start to retain a whole lot of the increased heat.
I just made some tea and poured it into a thick ceramic cup. The tea cooled a bit as the cup heated and became drinkable. Eventually the tea got cold even as the cup remained warm.
Now if I used a more perfect insulator like a Styrofoam cup, the cup would be cold, and the tea maximally hot. That is with 100% CO2 every infrared would hit a Co2 molecule and the bounce would be (assume the Earth absorbs 1/2 and reflects 1/2) 1/2 + 1/4 + 1/8 ...
But with some other density where the infrared can get "into" the CO2 layer, it could be 1/4 + 1/32 + ...
So do we end up with a heated layer of CO2 gas surrounding the planet which maximally keeps infrared both from the stratosphere and from the Earth body?
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Coby Beck Posted 2:38 pm
13 Sep 2008
energy in must equal energy out
jabailo,
No matter what the the content of the atmosphere, when at equilibrium, the earth will be radiating out as much energy as is coming in. Right now, during a state of disequilibrium, the radiation leaving the top of the atmosphere should be less, the difference going into warming the surface layers. Elevated CO2 will cause infrared to stay in the system longer, but ultimately the same amount will escape (aagain, once the sutem has acheived a new equilibrium)
"What if this weren't a hypothetical question?" -- unknown
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amazingdrx Posted 3:45 pm
13 Sep 2008
Good job Coby
Thanks so much for your valiant efforts, over so many articles. You have some titanic patience!
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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MAD MAC Posted 3:54 pm
13 Sep 2008
I still think it should be possible........
........ to modify the troposphere or the stratosphere in order to reduce the energy coming to the surface and thus mitigating the problem via this method.
Also, it seems we really need to put more effort into CO2 "washing" to remove CO2 that is already in the atmosphere.
These two actions could go a long way towards cooling the climate and achieving equilibrium, but I don't hear climate scientists beating the drums for them. Why not?
Truth be told, even if the west reduces its greenhouse gases, the Developing world is just going to take our place in outputs. The oil is giong to be used until it's gone. That's pretty obvious.
Victory in Pattani
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WWAGD?! Posted 3:58 pm
13 Sep 2008
No, Doesn't Follow
" Elevated CO2 will cause infrared to stay in the system longer"
On that we may may possibly agree.
"but ultimately the same amount will escape (aagain, once the sutem has acheived a new equilibrium)"
Not necessarily. With a thick enough layer of Co2, it would be the Co2 itself that husbands the energy.
So, it radiates up, hits on Co2 molecule, then another, then another. The odds of it "coming out" decreases with its efficiency as an infrared capturing layer, and the odds of it "staying in" -- constantly hitting other CO2 molecules rises.
Another result of this is that the heat would be spread with infrared travelling sideways in the layer. This could explain why the tropics aren't heating much, the temperate zones more and the polar zones a lot.
..in addition, any natural radiation from the Earth itself will also be trapped there, so the result at this optimal Co2 density would be a cooling of the planet with an ever hotter Co2 layer.
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SamHec Posted 4:22 pm
13 Sep 2008
Sequestration
of carbon molecules which store energy in their connections can eat up some of the expected outgoing IR radiation....but Eventually there will -otherwise- be equilibrium, as other Climate mechanisms stop reacting to the CO2 temp forcings, and give up latent energy as heat.
WRT satellites to measure such changes....well Al Gore wanted to launch DSCVR aka Triana aka GoreSat to do just that. But a certain political faction, who was in love with Hating Al Gore, would have nothing of it...that and the Shuttle crashed again.
This is STILL not a Signiature!
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amazingdrx Posted 4:32 pm
13 Sep 2008
Manufacturing and ag
"...even if the west reduces its greenhouse gases, the Developing world is just going to take our place in outputs."
In the developing world is already doing this, wether we reduce GHG or not. A lot of it to produce goods we use. All the cheap food and cheap junk at places like Walmart for instance.
They burn rain forest, vomit toxins, and spew coal emmisions elsewhere to stock the shelves here in the US.
The way to change this is to lead. We invent and mass produce and use rewable/conservation energy devices and those nations will rush to copy us and do it cheaper. And in the process realize these devices are a better deal economically for them too.
Saving the climate wouuld be a byproduct. When they see it makes money for them to be green, they will pretend to do it for the environment, then that takes on a self fullfilling nature. You might call it psychological/cutural postive feedback effect, hehey. So it goes.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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Russ Posted 5:59 pm
13 Sep 2008
shared emission responsibility
drx says
Which is in part why the delayer catch-22 talking point that America shouldn't impose a carbon price until China's willing to do so as well is fraudulent - a significant part of China's emissions are also America's emissions.
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amazingdrx Posted 6:14 pm
13 Sep 2008
Yep Russ
Delay and go the way of the all other empire.
Lead, follow, or get out of the way. With Palin/ McCain we will be in the way, as under duuhbya.
We still might be a contendor in terms of positive historical leadership. But that window will close with more of this drill, baby, drill and oil warrior bunk.
Gore's revenue neutral carbon tax/income tax cut for those under 200k is the way to go. And diverting carbon subsidies to GHG free subsidy.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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Russ Posted 6:55 pm
13 Sep 2008
positive historical leadership
That's what I've always said - enough already with these cost-benefit obsessions, all these accountants banging away like monkeys with typewriters trying to replicate Shakespeare.
What's needed is a grand historical gesture to break out of this morass, and even after all the damage eight years of aggressive idiot rule has done, the idea of America still commands enough respect, admiration, and hope worldwide that a grand moral gesture on America's part could still turn the tide around the world.
America should have, not the miserable myopia of a money-changer, but the pride of a leader.
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amazingdrx Posted 12:58 am
14 Sep 2008
Subsidy diversion
If Obama and the democratic controlled legislative branch would take a leap and divert the 10s of billions in corporate welfare and subsidies for fossil and nuclear and agribizz fuel farming to provide direct subsidies to homeowners and businesses to install solar panels and switch to plugin hybrids and ground source heating/cooling, that would get this energy revolution going.
It would mean turning on lobbyists and the powerful interests they support.
With direct subsidies utilities could build out smart grids to handle the power from solar, wind, and biogas and store it in plugin hybrid batteries and as heat or cold in building mass. They could even start to incorporate wind pumped hydro storage in existing hydro dams and super conducting electromagnetic energy storage systems.
With some of the subsidy money diverted, government could negotiate orders for millions of plugin hybrids, solar systems, and ground source heating/cooling systems, spurring mass production right here in the US. Stimulating our manufacturing, job, and tax base.
Subsidy diversion is a revenue neutral plan that could pay down our debts public and private. Russia has payed down it's debt in the last decade. How?
With oil and gas revenue, on the backs of European and US citizens. They are becoming a financial and world power again. We can see the danger that presents with the incursion into Georgia and the necon shill palin response. War!
The Palin/Mccain plan? Drill and wage war and go bankrupt with debt owed to China and OPEC nations, we see how that plan is working.
That's not change. That's more of the same. Hehehey. Oh, we got our slogans too. But they actually make sense.
http://amazngdrx.blogharbor.com/blog John Schneider, Northern Wisconsin
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WWAGD?! Posted 4:53 am
14 Sep 2008
Hybrid Shills
"It would mean turning on lobbyists and the powerful interests they support. "
Har. It's so hypocritical of you to disparage one industry simply to shift funds to your own favorite group of cronies: T. Boone Pickens and the Wind Combine, or the Solar Cartel or the Hybrid Hunta.
You clearly are taking a side, not offering some panacea. (I do the same, but I admit it...openly).
Why not hydrogen. Why not fuel cells. Why not cars that only have one engine...run on hydrogen generated from water using the Nocera method?
Yes, brush all that under the rug, Democrats, because it prevents you from getting the pork and earmarks put into your blue wallets!
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WWAGD?! Posted 4:57 am
14 Sep 2008
Clarify
"but Eventually there will -otherwise- be equilibrium, as other Climate mechanisms stop reacting to the CO2 temp forcings, and give up latent energy as heat."
Well, I think I understand you, but I get worried when things start to drift from technical descriptions to semi-metaphor.
Could this be said: At some point the total number of CO2 molecules will be active, charged up from an infrared ray, and unable to absorb any more?
At that point, any infrared heading into the Troposphere's CO2 layer would freely pass into the Stratosphere, unable to find an "open" Co2 molecule.
However, when you say "Climate mechanisms stop reacting", I really need a bit more specifics...
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GRLCowan Posted 6:32 am
14 Sep 2008
Oil can be leapfrogged
So far, the only large-scale permanent CO2 removal that has been happening, has been happening as a side effect of mining. More here, including numerous comments by me up and down thread.
They tend to think once CO2 has dispersed in the atmosphere, condensing it to a solid must be very difficult, because its entropy in the solid will be less. Fortunately, they are wrong, because the heat released by the condensation increases total entropy more. So grains of pulverized alkaline earth silicate minerals are consumed by, and consume, atmospheric CO2 over a period of one to five years. Here's Schuiling again saying one year (but he wants it to happen in warm places, where it's quicker).
Western governments are already taking enough special revenues on oil and gas to pay for removing CO2 by the above-mentioned methods at a greater rate than it is being injected from all fossil fuels worldwide. We could carry the developing world.
Also, in some markets, we know oil can be beaten, because it has been. Natural gas is next, as soon as its wind-power figleaf can be stripped away.
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SamHec Posted 10:33 am
14 Sep 2008
Replies
"the Hybrid Hunta."
iz spelld 'Junta'. ;)
"Yes, brush all that under the rug, Democrats, because it prevents you from getting the pork and earmarks put into your blue wallets!"
My oft repeated proposalis to simply end ALL energy subsidies and market protections, and replace subsidies for renewable energy by simply having our governments pay Certified Carbon Offsets for their own greenhouse gas wastes. It pays for itself, it's self-deleting, and the Free-MarketTM figures out where best to spend the money. It's probabvly not enough to get us back down to 350ppm of CO2, but it's a good start. And while we're at it, kill the Farm Bill; the changing climate will be too weird to be picking winners and be wrong anyway.
"Could this be said: At some point the total number of CO2 molecules will be active, charged up from an infrared ray, and unable to absorb any more?"
That is a very interesting question, I don't have an answer, but it probably relates to logarithmic (not one-to-one) relation between CO2 Levels and Global Temperature.
"However, when you say "Climate mechanisms stop reacting", I really need a bit more specifics..."
Inertia. To be more exemplific (NEW WORD!), the brakes in your car don't create an instantaneous stop.
This is STILL not a Signiature!
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