What If There Was No Greenhouse Effect?
by Roy W. Spencer, Ph. D.
The climate of the Earth is profoundly affected by two competing processes: the greenhouse effect, which acts to warm the lower atmosphere and cool the upper atmosphere, and atmospheric convection (thermals, clouds, precipitation) which does just the opposite: cools the lower atmosphere and warms the upper atmosphere.
To better understand why this happens, it is an instructive thought experiment to ask the question: What if there was no greenhouse effect? In other words, what if there were no infrared absorbers such as water vapor and carbon dioxide in the atmosphere?
While we usually only discuss the greenhouse effect in the context of global warming (that is, the theory that adding more carbon dioxide to the atmosphere will lead to higher temperatures in the lower atmosphere), it turns out that the greenhouse effect has a more fundamental role: there would be no weather on Earth without the greenhouse effect.
First, the big picture: The Earth surface is warmed by sunlight, and the surface and atmosphere together cool by infrared radiation back to outer space. And just as a pot of water warming on the stove will stop warming when the rate of energy gained by the pot from the stove equals the rate of energy loss by the pot to its surroundings, an initially cold Earth would stop warming when the rate at which solar energy is absorbed equals the rate at which infrared energy is lost by the whole Earth-atmosphere system to space.
So, let’s imagine an extremely cold Earth and atmosphere, without any water vapor, carbon dioxide, methane or any other greenhouse gases – and with no surface water to evaporate and create atmospheric water vapor, either. Next, imagine the sun starts to warm the surface of the Earth. As the surface temperature rises, it begins to give off more infrared energy to outer space in response.
That’s the Earth’s surface. But what would happen to the atmosphere at the same time? The cold air in contact with the warming ground would also begin to warm by thermal conduction. Convective air currents would transport this heat upward, gradually warming the atmosphere from the bottom up. Importantly, this ‘dry convection’ will result in a vertical temperature profile that falls off by 9.8 deg. C for every kilometer rise in altitude, which is the so-called ‘adiabatic lapse rate’. This is because rising warm air parcels cool as they expand at the lower air pressures aloft, and the air that sinks in response to all of that rising air must warm at the same rate by compression.
Eventually, the surface and lower atmosphere would warm until the rate at which infrared energy is lost by the Earth’s surface to space would equal the rate at which sunlight is absorbed by the surface, and the whole system would settle into a fairly repeatable day-night cycle of the surface heating (and lower atmosphere convecting) during the day, and the surface cooling (and a shallow layer of air in contact with it) during the night.
The global-average temperature at which this occurs would depend a lot on how reflective the Earth’s surface is to sunlight in our thought experiment. ..it could be anywhere from well below 0 deg F for a partially reflective Earth to about 45 deg. F for a totally black Earth.
So, how is this different from what happens in the real world? Well, notice that what we are left with in this thought experiment is an atmosphere that is heated from below by the ground absorbing sunlight, but the atmosphere has no way of cooling…except in a very shallow layer right next to the ground where it can cool by conduction at night.
Why is this lack of an atmospheric cooling mechanism important? Because in our thought experiment we now have an atmosphere whose upper layers are colder than the surface and lower atmosphere. And what happens when there is a temperature difference in a material? Heat flows by thermal conduction, which would then gradually warm the upper atmosphere to reduce that temperature difference. The process would be slow, because the thermal conductivity of air is quite low. But eventually, the entire atmosphere would reach a constant temperature with height.
Only the surface and a shallow layer of air next to the surface would go through a day-night cycle of heating and cooling. The rest of the atmosphere would be at approximately the same temperature as the average surface temperature. And without a falloff of temperature with height in the atmosphere of at least 10 deg. C per kilometer, all atmospheric convection would stop.
Since it is the convective overturning of the atmosphere that causes most of what we recognize as ‘weather’, most weather activity on Earth would stop, too. Atmospheric convective overturning is what causes clouds and rainfall. In the tropics, it occurs in relatively small and strongly overturning thunderstorm-type weather systems.
At higher latitudes, that convection occurs in much larger but more weakly overturning cloud and precipitation systems associated with low pressure areas.
There would probably still be some horizontal wind flows associated with the fact that the poles would still be cooler than the tropics, and the day-night heating cycle that moves around the Earth each day. But for the most part, most of what we call ‘weather’ would not occur. The same is true even if there was surface water and water vapor…but if we were able to somehow ‘turn off’ the greenhouse effect of water vapor. Eventually, the atmosphere would still become ‘isothermal’, with a roughly constant temperature with height.
Why would this occur? Infrared absorbers like water vapor and carbon dioxide provide an additional heating mechanism for the atmosphere. But at least as important is the fact that, since infrared absorbers are also infrared emitters, the presence of greenhouse gases allow the atmosphere — not just the surface — to cool to outer space.
When you pile all of the layers of greenhouse gases in the atmosphere on top of one another, they form a sort of radiative blanket, heating the lower layers and cooling the upper layers. (For those of you who have heard claims that the greenhouse effect is physically impossible, see my article here. There is a common misconception that the rate at which a layer absorbs IR energy must equal the rate at which it loses IR energy, which in general is not true.)
Without the convective air currents to transport excess heat from the lower atmosphere to the upper atmosphere, the greenhouse effect by itself would make the surface of the Earth unbearably hot, and the upper atmosphere (at altitudes where where jets fly) very much colder than it really is.
Thus, it is the greenhouse effect that continuously de-stabilizes the atmosphere, ‘trying’ to create a temperature profile that the atmosphere cannot sustain, which then causes all different kinds of weather as the atmosphere convectively overturns. Thus, the greenhouse effect is actually required to explain why weather occurs.
This is what makes water such an amazing substance. It cools the Earth’s surface when it evaporates, it warms the upper atmosphere when it re-condenses to form precipitation, it warms the lower atmosphere through the greenhouse effect, and it cools the upper atmosphere by emitting infrared radiation to outer space (also part of the greenhouse effect process). These heating and cooling processes are continuously interacting, with each limiting the influence of the other.
As Dick Lindzen alluded to back in 1990, while everyone seems to understand that the greenhouse effect warms the Earth’s surface, few people are aware of the fact that weather processes greatly limit that warming. And one very real possibility is that the 1 deg. C direct warming effect of doubling our atmospheric CO2 concentration by late in this century will be mitigated by the cooling effects of weather to a value closer to 0.5 deg. C or so (about 1 deg. F.) This is much less than is being predicted by the UN’s Intergovernmental Panel on Climate Change or by NASA’s James Hansen, who believe that weather changes will amplify, rather than reduce, that warming.
RE: bob (14:18:37) :
“You don’t need the greenhouse gases to cool the atmosphere, oxygen and nitrogen are infared emitters according to the Planck black body radiation effect.
So the atmosphere cools without the greehouse gases.”
Gases are not blackbodies!
To the limited extent that O2 has an IR spectrum one should include it as acting weakly as a greenhouse gas. Just imagine a Helium only atmosphere and you will have something like an GHG free, IR transparent atmophere.
Alex
Mh no weather without the green house effect , this guys thinks different :
http://freenet-homepage.de/klima/atmoseffect.htm
All exchanges happen in the whole range of wave lengths. Our limitations as observers do not condition the phenomena ocurring in nature around us. They happen without our consent.
Here is an online pdf of Bejan & Reis Thermodynamic optimization of global circulation and climate Int. J. Energy Res. 2005; 29:303–316. They show Constructal theory predicts global circulation.
“Mike D. (16:13:33) :
[…]
I may have missed it in the verbiage above, but my impression, unscientific though it may be, is that the ROTATION of the Earth about its axis every 24 hours, at speeds approaching 1,000 miles/hour at the Equator, and the angular momentum therefrom, have something to do with the WIND”
In the beginning the Earth stood still. And the atmosphere stood still.
Then came a cosmic billard queue and set the Earth in rotating motion with a 1000 miles an hour. As the atmosphere was not affected by this, it came to be that there was a 1000 miles/hour wind.
Actually, this didn’t last too long as friction set in and accelerated the atmosphere until it had exactly the same speed as the rotating earth. The earth slowed down a tiny bit to keep the angular momentum in balance.
There is no absolute speed, speed is relative. The atmosphere would rotate with the planet.
No water vapor huh? That means no water. Which means no life, so who cares?
Has anyone postulated a mechanism for the “flow,” for lack of a real word, of CO2 particles in the atmosphere?
Back in the days of the chlorofluorocarbon scare, the New Yorker managed to publish a readable article in which they explained how those little CFC beasties managed to get up to the ozone layer, how they engaged in chemical interactions that “ate” the ozone, why the “ozone holes” were over the poles and so on. Lots of wonderful stuff. I haven’t seen anything comparable for the CO2 particles that supposedly cause global warming. Does anyone know of postulated mechanisms that are taken to be important by some researchers?
I doubt that there is a postulated mechanism that is taken seriously. I just read an in article in “Science News” which argued that there has been no increase in the CO2 concentration in the last 150 years. Obviously, if that conclusion has merit then there is no mechanism because, if it existed, it would have no effect.
If there is no mechanism that has some support, then the Climategaters were doing only temperature reconstruction from historical records. That is the extent of their science, I take it.
“David L. Hagen (16:34:54) :
[…]
The new climate theory of Dr. Ferenc Miskolczi”
Oh. I guess that settles the debate for good, then.
The cyclic processes of evaporation/condensation and freeze/thaw are the energy exchange controlling factors that result in weather and climate change in this water world of ours. These processes would continue without any atmospheric CO2 .
GHG act as a buffer. The IR still ends up in space, and is not trapped, just delayed, like traffic. In the end, everyone gets home in space. The net energy flux of IR is still bottom to top.
Not sure why the upper atmosphere should cool since after a steady state is reached, just as much IR is released to space though the upper atmosphere.
Also the upper troposphere has not warmed even though there is more CO2 to capture outgoing IR. I suppose the density is quite low, so perhaps the GHG effect is minimal there, also because there is little water vapor at that altitude, and H2O is the most important GHG. In the desert, it gets cold in the evening, even with all that CO2, since there is not much humidity.
We have geothermal heat, coriolis forces on wind and ocean currents, moons influence on tides, energy being captured for photosynthesis, changing albedo, heat transport to poles from tropics, latent heat, adiabatic expansion, solar variability, air exchanges with the stratosphere, all of which influence on the weather and climate. Simple models do not work, and computers are not fast enough to handle more complex models .
A 1 deg C temperature rise due to CO2 is a 0.37% temperature rise, yet a doubling of CO2 is only a 0.038% increase in atmosoheric CO2. Thats an order of magnitude difference.
I would love to see an energy or heat content balance broken down by components in the atmosphere , O2, CO2, H20, latent heat, etc by altitude, and the net fluxes upward and downward. I mean, how much heat relative to total atmospheric heat is a result of CO2’s IR absorption at a given moment in time.
The article kind of muddies the water since the real issue is CO2 (and I am am Spencer fan), but it does point out how important H20 is. Just don’t confuse H20’s importance with CO2.
“DirkH (17:08:26) :
Oh. I guess that settles the debate for good, then.”
To elaborate further for all who don’t want to look through Ferenc’s slides, the key sentence is:
“If the system energetically could increase its
surface temperature, it need not wait for our
anthropogenic CO2 emissions, since another
GHG, water vapor, is available in a practically
infinite reservoir, in the surface of the
oceans.”
And as far as i understood it, the system tries to reach an
optimum point were exactly 1/3 of the IR radiation is
coming back to earth; it can’t do any better so that’s the optimum.
As the transmission function has exactly one maximum,
it will go there. Ferenc compares his theoretical assumptions
with experimental data and concludes that earths atmosphere is
working close to the optimum.
At least that’s my understanding. Didn’t see these slides before,
didn’t really get the point of his theory before. It’s beautiful.
The greenhouse effect can be physically explained without the greenhouse gases. There would be weather without those radiation absorbing gases and we wouldn’t have to account for the thermophysically questionable surface warming backradiation.
Hans Jelbring, The “Greenhouse Effect” as a Function of Atmospheric Mass
http://www.ingentaconnect.com/content/mscp/ene/2003/00000014/F0020002/art00011
http://www.tech-know.eu/NISubmission/pdf/Politics_and_the_Greenhouse_Effect.pdf
Dr. Spencer,
Not sure if I understand the distinction between these two processes since they are both primarily water vapor. It is easier for me to visualize water vapor functioning as a greenhouse when it simply is not energized enough to vent that energy convectively by rising into the cooler upper atmosphere and condensing.
Q: I understand the argument that C02 in low concentration has insufficient heat capacity to create catastrophic warming. And I can visualize that available IR is absorbed by water vapor within the first (X) feet of the surface until it is consumed, but:
What would happen if C02 was in concentration on par with water vapor? I should think it would begin to exert itself somewhere in a much higher concentration.
I found this to be a very interesting article (I like Dr. Spencer’s work), although I do not believe the so-called Greenhouse Effect Theory works anything like what I most often see being described. I don’t believe the so-called Greenhouse Effect Theory has the ability to heat anything, but instead slightly inhibits cooling or heat dissipation. I also believe that even the most conservative estimates citing a temperature differential between Greenhouse and non-Greenhouse are grossly over estimated. Meaning, the claims that we are 33C warmer with a Greenhouse Effect than we would be without, is grossly over estimated, and I believe the actual figure would be closer to single digits, if at all. The so-called Greenhouse Effect Theory does nothing more than slow the rate of cooling (inhibiting, or slowing, energy transfer).
– The Plinko Effect Theory –
The way I like to think of it is like this. Imagine for a moment a very stable atmosphere, without any wind or air movement at all. Now, release a ball filled with hydrogen or helium, this representing Infrared Radiation. The ball will swiftly float straight upward, accelerating until it reaches terminal velocity. Now, imagine GHG’s being represented by a matrix of static balls evenly spaced throughout that atmosphere (density of balls representing GHG concentration). Now, release another helium ball (IR). What happens? It bounces back and forth through the static balls (GHG’s), still gaining altitude, never descending, but ping-ponging between the static balls like a plinko-chip game (price is right). Any energy transfer that occurs simply spawns the same mechanism upward. The upward moving balls can never transfer energy downward.
Now, one might say, well the IR ball hit a GHG ball and bounced back down. Well, yes, that is possible, however, remember that there are other GHG balls bellow that the IR ball will likely plink off of and bounce right back up again, continuing its ascension as before.
Now, since our atmosphere is not static, and air can move somewhat upward and downward (vertical mixing), it is possible to get some of the balls moved to a lower altitude for a short period of time, but they will always persist in rising. So, at most, one could expect a very slight rise in the total density of lower altitude balls (very slight, and probably equates to more like 1C or 2C, not 33C). You are never able to increase the density of balls at the surface without first directly increasing the rate at which the surface releases those balls. The heat source is always the surface, and GHG’s can only slow the dissipation, and perhaps ever so slightly increase the density of balls near the surface through the so-called Plinko Effect Theory.
Personally, I believe this is a little more accurate representation of what really happens in our atmosphere than does the so-called Greenhouse Effect Theory.
The Earth is not warm because of GHG’s .. and Venus is not hot because of CO2 .. can’t work that way.
My imagination at work … yikes… 😉
almost forgot… I also left an email on your site asking if UAH Global Mean Temp is calibrated to surface records, and is there a risk that upward adjustments in the surface record would affect your results?
Different approach to the question.
What global climate forces brought on the Holocene? And how did those climate forces settle to maintain the Holocene?
What effect would greater or lesser CO2 have in that context?
If there are no answers to the first two questions, then how can the third question be answered?
Well, it can be answered by a look at the climate record of the Holocene, and so far the answer would be that CO2 has no discernible effect outside of normal variance within the Holocene.
If that’s true, then the forces that shaped and maintain the Holocene are not substantially effected and certainly not overridden by CO2.
The human effect on climate might be real, but it’s not substantial enough to be quantified, and not substantial enough to override the climate forces that maintain the Holocene.
I’d like to add another explanation about the mechanism described by the remarkable sentence by Ferenc M. Miskolczi .
For the moment, forget about CO2. Water vapour absorbs IR even better, that is why the IPCC always puts an emphasis on the water vapour “feedback”.
So earth heats up due to the greenhouse effect caused by water vapour. Now this will cause more IR radiation from the surface upwards and more water vapour.
This process continues for a while. Earth heats up, more radiation, more water vapour. Feedback.
But as we have learned: The absorption spectrum is saturated pretty fast and further increase of the concentration of a GHG has only a logarithmic effect on the increase in greenhouse effect. (A doubling in GHG leads to a constant addition in reflected IR)
So at a certain point, the feedback reaches the area of “diminishing returns”. For each new increase in temperature, more water vapour will rise into the atmosphere but on each feedback cycle the radiative effect of the added water vapour will decrease.
At least that’s how i understand it. And i find that an absolutely marvellous piece of work.
Wow. No greenhouse = no weather? Just ask the Martians where the winds surely do blow. Strange that a scientist from NASA would so mislead. All you skeptics out there: you might not want to use this site as your only education if this post is representative of the state of its science.
“When you pile all of the layers of greenhouse gases in the atmosphere on top of one another, they form a sort of radiative blanket, heating the lower layers and cooling the upper layers.”
Are we really adding any additional layers by adding CO2 to the atmosphere? If there is a saturation point of the infrared spectrum already in effect, the likely scenario is that the CO2 simply replaces other existing infrared absorbers and has no net effect at all. You cannot make a blanket more effective by squishing more insulation into the same few layers it already has. So, unless you can show how adding CO2 to the atmosphere in fact adds a layer of insulation between earth surface and outer space, the argument seems flawed. It is much more likely that adding 10 times the current CO2 content would actually equal the 1C increase in temperature than a simple doubling. I have no science to back this, just plain simple instinct on the fact that the earth is 4.5B years old, CO2 content has been 20 times as high as today while temperature at the time was comparable or even lower than today’s, and if there was a feedback mechanism for greenhouse effects, it would have already taken the earth to boiled ocean temperatures.
The rest of the article is cool and I dig it. I just get sick and tired of people trying to explain that CO2 adds to the greenhouse effect 1C per doubling as though there is no possible point of there being a saturation point.
“Paul (17:42:38) :
Wow. No greenhouse = no weather? Just ask the Martians where the winds surely do blow.”
They don’t have much precipitation up there or do they? BTW doesn’t Mars has a CO2 rich atmosphere? So there’s surely a greenhouse effect on Mars.
wikipedia about Mars: “The atmosphere on Mars consists of 95% carbon dioxide…”
Here i guess the wikipedia is not wrong….
Paul (17:42:38) :
“All you skeptics out there: you might not want to use this site as your only education if this post is representative of the state of its science.”
and yet here you are
peter_dtm (14:19:11) :
The only serious study I have ever seen on this debunked it quite effectively. The researcher started with several ‘sinks’, ie large containers with central drains, and left them for over 30 minutes to ‘settle’. This was the only way to ensure there was no effect from initial movement (which does some debunking already). His results then showed that the number of clockwise and anti-clockwise flows for all tests were statistically equal. I am not certain where he was based, but I am pretty certain in the US.
No idea where he got the research grant from. Probably claimed some future nebulous disaster, or something 😉
“Paul (17:42:38) :
Wow. No greenhouse = no weather? Just ask the Martians where the winds surely do blow. Strange that a scientist from NASA would so mislead. All you skeptics out there: you might not want to use this site as your only education if this post is representative of the state of its science.”
Maybe someone with an ignorance problem should go read about the actual Martian atmosphere content. Seems to me that the main gas in the atmosphere on mars is… wait for it… if you like to remain ‘ignorance is bliss’ stop reading now… CO2. oh, man, I bet that hurts like hell. Oh well, better luck next time Warmonger.
John A (14:22:37) :
Roy is talking about the planet Mars.
Unfortunately the notion that the lower atmosphere “warms” the surface is physically wrong – no more than double glazing “warms” the inside of a house
Perhaps phrased incorrectly.
Neither warms the earth or house, but it does change the rate at which the house or earth changes temperature.
Steve
DirkH (17:52): Mars does have a mostly CO2 atmosphere, but because of the very low surface pressure, it has little radiative influence and *** in the absence of a lot of dust ** the temperature of the surface of mars is very close to the radiative temperature (the mean temperature required to balance the absorbed solar radiation with outgoing IR). Dust is the main radiative forcing agent of the Mars atmosphere, but except during large dust storms, radiation from dust does not significantly heat the surface.