The greenhouse effect is real. If there were no greenhouse gases in the atmosphere, earth would be a cold place. Compare Mars versus Venus – Mars has minimal greenhouse gas molecules in its’ atmosphere due to low atmospheric pressure, and is cold. By contrast, Venus has a lot of greenhouse gas molecules in its’ atmosphere, and is very hot. Temperature increases as greenhouse gas concentration increases. These are undisputed facts.
outgoing radiation = incoming radiation – changes in oceanic heat content
The image below from AER Research explains the radiative balance.
http://www.aer.com/scienceResearch/rc/rc.html
About 30% of the incoming shortwave radiation (SW) is reflected by clouds and from the earth’s surface. 20% is absorbed by clouds and re-emitted back into space as longwave (LW) radiation. The other 50% reaches the earth’s surface and warms us. All of that 50% eventually makes it back out into space as LW radiation, through intermediate processes of convection, conduction or radiation. As greenhouse gas concentration increases, the total number of collisions with GHG molecules increases. This makes it more difficult for LW radiation to escape. In order to maintain equilibrium, the temperature has to increase. Higher temperatures mean higher energies, which in turn increase the frequency of emission events. Thus the incoming/outgoing balance is maintained.
Click for larger image
http://www.aer.com/scienceResearch/rc/m-proj/lbl_clrt_mls.html
The important greenhouse gases are: H2O, CO2, O3, N2O, CO and CH4. The reason why the desert can get very cold at night is because of a lack of water vapor. The same is true for Antarctica. The extreme cold in Antarctica is due to high albedo and a lack of water vapor and clouds in the atmosphere, which results in almost all of the incoming radiation returning immediately to space.
An earth with no CO2 would be very cold. The first few tens of PPM produce a strong warming effect, and increases after that are incremental. It is widely agreed that a doubling of CO2 will increase atmospheric temperatures by about 1.2C, before feedbacks. So the debate is not about the greenhouse effect, it is about the feedbacks.
Suppose that the amount of reflected SW from clouds increases from 20% to 21%? That would cause a significant cooling effect. Thus the ability of GCM models to model future temperatures is largely dependent on the ability to model future clouds. Cloud modeling is acknowledged to be currently one of the weakest links in the GCMs. Given the sensitivity to clouds, it is perhaps surprising that some high profile climate scientists are willing to claim that 6C+ temperature rises are established science.
So the bottom line is that the greenhouse effect is real. Increasing CO2 will increase temperatures. If you want to make a knowledgeable argument, learn about the feedbacks. That is where the disagreement lies.
Leif
Where do people get these ideas from? Googling the internet?
No ,this is textbook knowledge, which you usually embrace, why not this time?
foinavon (10:14:41) :
As usual you disparage all the previous theories and replace them with the newly concocted papers from the early 2000 to 2008. That makes me very suspicious and it should make you suspicious also. The fact that it doesn’t, speaks volumes to me. You should ask yourself how the font of all knowledge appears only in the last eight to nine years.
On the theme that you think life began only nine years ago you may be aware that there was a medieval warm period and a little ice age. Outside of your own fledgling scientific field all other facets of science acknowledged these historical periods. Unfortunately these periods run contrary to the CO2 thesis. Then along came Mann and his bent hockey stick and the rewrite of historical temperature records commenced. Even though Mann’s work has become the most discredited piece of climate science, along comes a whole raft of other studies purporting to show variants of the hockey stick. Naturally all of these studies are post Mann. None of them pre-date him. Coincidence? Not likely.
And Anthony, it’s not a question of over analysing. Foinavon will argue black is white as long as it is in defense of that beloved molecule, CO2.
When I was in college, we were taught how to solve equations with two or three variables. We applied this math to try and figure out how electric motors really worked so we could predict horsepower output and efficiency. When the professor started writing down all the variables (about 15 or twenty in all), we found it impossible to calculate the output. Of course, the professor already knew this. It got worse when we tried to figure out how radio antennas really work (some configurations are pretty exotic). Even the experts admit that some of this is black art with trial and error because of all the variables and our lack of understanding of certain aspects of electromagnetics.
So after reading all this back and forth. I started thinking of the THOUSANDS (if not more) of variables far beyond the very few mentioned in the arguments in the comments to this posting).
There is no way any supercomputer can be set up to model all the variables on the Earth and coming at us from the sun, etc.
Mr. Goddard’s simplistic post on the greenhouse effect doesn’t do anything to show CO2 affects us at all, and is a disappointing primer no better than telling my son that the reason a car works is because you put gas in it and push on the pedal. To understand it, you need to know what’s under the hood.
So how did we finally figure out the horsepower and efficiency of the motor, or the effectiveness of a radio antenna? We tried it out, tweaked stuff, recorded data and drew conclusions. We dropped the idea of calculating or modeling how the stuff worked.
So back to the Greenhouse: I simply watch the satellite data and see the temperature statistics over time. The Arctic icecap did not melt last summer, and it doesn’t look like it will before I’m gone. And no one seems to be able to find arguable evidence of the oceans rising at historic tidal water marks at various locations around the Earth from these past centuries.
Sometimes observation over time, is better than trying to predict 50 years into the future with math we just can’t solve.
Joel Shore:
That being the case, and I agree btw, how can they predict temperature increases of several times what can be attributable to CO2 forcing?
Steve,
Looking at three planets and saying that as greenhouse gas concentration increases so does temperature does not really settle the issue for me I’m affraid. The proxy record of fluctuating CO2 and temperature indicates quiet clearly to me that radiative heat transfer is by far not the dominant heat transfer mechanism in the earths atmosphere. Increased temperature increases verticle wind shear. To put it in terms of your car analogy CO2 would add an extra traffic light on the road between your school and place of work, but then verticle wind shear would go and put an expressway between them.
Colonel Sun (10:14:32) :
Mark (06:36:27 wrote :
“Has there ever been a study that involved a bunch of greenhouses where each had different amounts of CO2 (all other factors equal) and all subjected to the same amount of sunlight to see how the different CO2 levels affect temperature?”
Winner, winner, chicken dinner. Excellent question.
Or take two “aquariums” with walls of whatever material is most transparent to infrared.
One filled with normal atmosphere and one filled with pure CO2. Both partly filled with water.
Shine infrared lights on both. Any difference in the rise in and final equilibrium temperature of the atmospheres and water?
REPLY: The experiment is too simple to replicate our atmosphere – Anthony
The experiment is not about replicating the atmosphere, but empirically evaluating the efficacy of CO2 as a greenhouse gas relative to the atmosphere.
As for Venus and Mars, the 1/r^s of solar radiation is the dominant effect.
Joel Shore (12:44:28) :
“No it doesn’t. If the positive feedback is sufficiently strong that the first order response is greater than the original effect (e.g., if the temperature response from feedbacks is greater than the bare response), then you have a diverging series and you are correct. However, if the positive feedback is weaker than this, then what you get is amplification, for example: 1 + 1/2 + 1/4 + 1/8 + 1/16, an infinite series that converges to 2.”
Not again Joel please. It’s getting like Ground Hog day.
Joel Shore 12:44:28
“I think that most climate scientists would say that a net positive feedbacks is very likely,….”
I watched the you-tube debate at the JLF foundation. It was my impression that experimental evidence at this point is that feedback is negative. No evidence for positive feedback.
jae (14:15:27) :
Thus, an increase of 8% water vapor would amount to only (0.08)(15) = 1.2 wm-2. Negligible.
Accepting your figures for now, that’s equal to 75% of the current net anthropogenic forcing. Why negligible? CO2 doubling is likely to be reached by the 2050s at current rates. So, to put it in simplified terms then, by your calculations we are looking at 1.2C + 0.9C = +2.1C by the 2050s. How ‘negligible’ is that?
Steven Goddard (10:04:26) :
**Cold air over ocean causes fog, which blocks LW. During the miserably cold California summer of 1998, I remember that we were lucky to get an hour of sunshine at noon on the beaches south of Santa Cruz. I also remember bundling up in several blankets to watch the fireworks.
“The coldest winter I ever spent was my summer in San Francisco”
Mark Twain
Sorry I meant to say that fog blocks SW (not LW) which is the dominant factor during the day. LW blocking is more interesting at night.**
Steve, you have it backwards in the first sentence. The cold air over the ocean does not cause fog because it would get heated and develop into convective cloud. That is how you get showers or snow showers in the winter further north. Advection fog develops when warm moist air moves over cooler water. Radiation fog develops over land at night when land cools due to LW radiation.
SW radiation heats the water, but because it penetrates up to hundreds of feet the daily change can only be a fraction of a degree. It takes a long time to heat water. The Great Lakes take a couple of months to get to 15 to 20 degrees. There is a similar effect for cooling. Water will cool by emitting LW radiation, but it also emits from the depths so it can only cool a fraction of a degree overnight and therefore radiation fog cannot form over water. This is why the Great Lakes do not freeze during an average winter. Lake Erie being the most shallow will freeze first.
On the other hand LW radiation emitted from land can drop the temperature 20 to 30 degrees overnight(on a clear night).
Cloud cover will reradiate the LW back down and slow the cooling.
That should be 1/r^2
Simon: That’s WATTS, not degrees. 3.7 watts translates to 1.2 C; so 1.2 watt translates to only 0.39 C. And that’s a worst-case scenario.
jae:
Death Valley is about as low a desert as you can get (it’s below sea level). In July, the average temperature range is for the high is 115 with an average low of 86, according to the weather channel.
Disclaimer: I don’t know exactly where the official temperatures are recorded in Death Valley. Death Valley is about as dry and barren as you can get, and is surrounded by mountains on all sides. There is no urbanization there, but official temps could be affected by land use changes near the weather station.
There should be comparable high desert sites nearby for comparison. What’s the altitude of Baker, CA? It’s not far from Death Valley (and is home to the world’s largest thermometer, btw) and except for possible local siting issues, there isn’t any urbanization to speak of in Baker, either. Weather.com shows the July average ranges from 108 to 76.
John Galt.
Here is information about measuring temperature in Death Valley.
Would it be wrong of me to wonder, after reading through this primer and the reactions, that the “greenhouse effect” might be an overly simplistic metaphor. Greenhouses do not warm for reasons anything like the greenhouse effect. It almost seems that the atmosphere is acting as “thermal mass” slowing the process of re-radiation.
I understand that absent an atmosphere the surface of the moon has greater temperature extremes than the earth, but maybe it would be good to consider how subsurface soil temperatures might behave when comparing the moon to the earth. After all, absent an atmosphere, the moon’s surface is more akin to the our boundary of space than the earth’s surface.
It’s easy to program: Just put in the observed temperature rise from 1979 to 1998, then program the computer to maintain the trend! Viola – runaway AGW!
The next step is to concoct an explanation of how this might work, and vigorously defend your results no matter what the actual temperatures are.
The point being: Computer programs only do what the programmer tells them to do. GIGO is the first thing I learned from my first programming class (Fortran, btw). This means Garbage In, Garbage Out.
Climate models show future warming simply because that’s what they were written to do. If you assume more CO2 causes more warming and you also assume there will be increased CO2 in the future, what other output could the models possibly have?
James Griffiths (13:05:33) :
Joel Shore says: (albeit a quote from someone else):
“The surface of the Earth is warmer than it would be in the absence of an atmosphere because it receives energy from two sources: the Sun and the atmosphere.”
I suppose that should be quantified (at least as I understand it)
The atmosphere (and the oceans) cool the surface while the sun is shining upon it, and prevent heat from leaving as quickly it might otherwise when the sun is not shining on it, thereby maintaining a mean temperature that we calculate is higher than might otherwise be the case.
The surface of the earth receives little energy from the atmosphere, it receives the energy from the sun. A proper diagram would show this.
SUMMARY: The earth receives all its energy from the sun by SW radiation. This heats the surface of the earth. The surface of the earth (land and water) then heat the air next to it by conduction and this is redistributed by convection, horizontal motion, evaporation and condensation. A small amount of heating of the atmosphere is caused by LW radiation emitted by the land and water.
Briefly, when the average temperature of the earth is not changing, the earth emits (loses)by LW radiation the same amount of energy it has received by SW radiation.
The earth is always emitting LW radiation. Any object above absolute zero emits LW radiation. When the sun is shining you have a net gain of SW over LW. AT night you have a net loss. AS you go towards the poles you have a net loss especially over the south pole where there is little dark surface to absorb the SW. Ocean and atmospheric circulation redistribute the heat energy.
Clouds modify the rate at which parts of the surface lose energy.
tmtisfree says:
Others have already responded to this but I will just add my voice: The second law says only that the NET flow of heat can’t be from the cooler atmosphere to the warmer surface without work. I.e., all that is required is that there is more heat flowing from the surface to the atmosphere than vice versa.
You might think, “Well, how then can the atmosphere heat the surface if the NET heat flow is from surface to atmosphere?” The answer to this conundrum is that the comparison case (the “control” if you will) is the case where all the heat from the earth’s surface escapes into space with none of it being returned to the surface by the atmosphere. So, anything that the atmosphere does return, even if only a fraction of what it receives, is extra heat to the surface.
Indeed. However, it is also true that misconceptions about a process breaking physical laws also need to be considered. The Second Law of Thermodynamics is a very powerful tool…But, with that power comes the possibility that it can be abused. G&T abused it by applying it incorrectly.
First, I want it clear that I don’t buy into Steve Goddard’s simplified radiation diagram. As many previous comments have noted, the earth’s absorption, distribution, retention, and transmittance of heat is an extremely complex phenomenon. With that caveat, however, I’m going to take Steve Goddard’s suggestion to heart and try to learn more about “feedbacks”. As I see it, AGW alarmists treat increasing atmospheric CO2 levels as both an original forcing function and as a feedback process. I’d like to know which if either (both) of these roles is paramount.
First role, increasing CO2 levels are feedbacks. AGW alarmists argue (or at least at one time Al Gore so argued) that based on data from Antarctic ice core samples, (a) over the past approximately 600,000 years there was a high correlation between Antarctic temperature fluctuations and Antarctic CO2 levels, and (b) that this correlation proves that increasing atmospheric CO2 levels caused increasing atmospheric temperatures. Aside from the logical fallacy that “correlation establishes cause and effect”, the AGW alarmists had to adjust their “proof” when it was leanred that Antarctic temperature changes preceded Antarctic CO2 changes by approximately 1,000 years. The AGW alarmist’s adjusted argument is that although some physical phenomenon other than increasing CO2 levels originated Antarctic temperature increases, the original increased temperatures released CO2 into the atmosphere, and the released CO2 amplified the original temperature changes. Thus in the adjusted AGW alarmist argument, atmospheric CO2 release is a “positive feedback”, not the originating phenomenon.
Second role, increasing CO2 levels are an original forcing function. AGW alarmists argue that via the burning of fossil fuels, man’s release of CO2 into the atmosphere will cause the average global temperature to increase by anywhere from 0.5 to 1.2 degrees centigrade. Since it’s hard to argue that this modest temperature rise will induce the catastrophic effects needed to impose draconian reduction in fossil fuel energy production, the AGW alarmists further argue that man’s release of CO2 will trigger non-CO2 feedbacks that will result in larger temperature increases–by as much as five degrees. In this second AGW argument, atmospheric CO2 release is the originating phenomenon, not a feedback.
So the AGW alarmists have increasing CO2 levels acting as both an originating and a feedback phenomenon. I’d like to know which if either is correct. Now it’s conceivable that increasing CO2 levels are both. However, if both, then what stopped runaway global warming in the past? The second AGW alarmist argument (an increasing CO2 level is the originating forcing function) states that a doubling of atmospheric CO2 levels will via non-CO2 feedbacks cause a temperature increase of approximately three degrees more than the originating temperature increase from increasing CO2 levels. The first AGW alarmist argument (an increasing CO2 level is a positive feedback) states that an increase in temperature will cause the release of additional CO2, which will act as a feedback and cause additional increases in temperature. Somewhere in all this confusion it seems to me we may have a runaway feedback process. After all, the AGW alarmists argue that temperature deltas at the system input produce larger temperature deltas at the system output. If the larger temperature deltas at the system output are “fed back” into the system input, why won’t they cause even larger temperature deltas at the system output, which when fed back to the system input cause even larger temperature deltas to the system output, etc. If it exists, I’d like to see a “circuit diagram” of the AGW alarmist’s temperature model where (a) the model inputs and outputs are defined, (b) all feed-forward effects (delays and multiplication factors) are shown, and (c) all feedback effects (delays and multiplication factors) are shown. For a specified input, such a diagram could then be used to predict the time behavior of the system output. If such a diagram doesn’t exist because (a) the delays are time varying, or (b) the multiplication factors are time varying, or (c) the system can’t be modeled using a linear feed-forward/feedback structure, or (d) [my choice] the system is just so complicated it can’t be represented using feed-forwards, feedbacks, and multipliers, then please give me a mathematical representation of the system (not just words, but a well-defined set of rules) so that others can analyze the system’s behavior. If the AGW alarmist’s can’t provide such a mathematical description, then PLEASE QUIT TELLING THE WORLD WHAT IT MUST DO TO PREVENT CATASTROPHIC GLOBAL WARMING.
Well, in a very rough sense, both act by trapping heat that would otherwise escape. However, the mechanism by which the heat is trapped is very different for a greenhouse as it is for the atmospheric greenhouse effect. So yes, it is well-understood that “greenhouse effect” is somewhat of a misnomer (see, e.g., what Wikipedia says about it: http://en.wikipedia.org/wiki/Greenhouse_effect ) but it happens to be the name that we ended up with historically.
Mark_0454 says:
That may be your impression from watching that debate but the actual fact is that most of the observational evidence in the peer-reviewed literature is precisely the opposite of your impression.
John Galt says:
That is not really a correct description. The global climate models are programmed with the best understanding of the actual physical processes involved. Some of this knowledge is admittedly better understood than others (e.g., radiative forcing due to greenhouse gases – well understood, radiative forcing due to aerosols – less well understood).
There is also a lot of data out there to test the models against (current climatology, the 20th century climate record, the Mt. Pinatubo eruption, the ice age – interglacial cycles, …)
jae, I know you’re talking watts. Actually your figure of 1.2 isn’t all that far away from the IPCC’s models’ mean of 1.80 ± 0.18. Lapse rate is negative, -0.84 ±0.26 W m–2. The big uncertainty is cloud feedback, with a mean of 0.69 W m–2 but a large spread of ±0.38 W m–2. Surface albedo feedback is 0.26 ±0.08 W m–2 .
Dave L I have a few questions for you:) (never met anyone with a greenhouse) In your greenhouse when you raise Co2 do you have to turn on the airconditioner? From day to night at an increased level of Co2 does your daytime temp spiral out of control unless you adjust it manually?.. And Im guessing you have to constantly replenish the Co2.. it just doesnt get there and stay does it?
Venus and Mars are for all general purpose devoid of life as we know it. No plants, no people. You cannot compare. We are part of a rather large cycle of biological chemistry that those planets do not know.
Another question for everyone. If Co2 can absorb reflected energy at a specific wave length, doesnt it also absorb incoming energy at that same wave length, keeping it from its destination? So what percentage of the incoming energy is absorbed and immediately dispursed back to space by a higher Co2 content. What percentage is redirected into a different wave before it even reaches earth. What percentage is slowed to the longest wave and “trapped” within our atmosphere unable to reach escape velocity. And doesnt it seem strange we are talking about such a narrow bandwith changing our entire climate?
Ok lets add to that. At the height of a solar cycle, particle density arriving from the sun increases. We have seen in years of the last solar maximum events that drove our meters off the chart. Not all of these were deflected by our magnosphere. In fact, in some cases our “tail” snapped back infusing our atmosphere with energised particles. So what percentage of our warming was due to having energised matter infused into our atmosphere. I have yet to see a study of what happens to that energy on whatever frequency it comes at except that sometimes it makes pretty northern lights. The sun earth interaction needs way more study than Co2. I think our quiet sun is teaching us a lot right now. We are seeing individual events and are more able to study the individual effects. It could be the real age of enlightenment, if the dark ages folks would just give up gloom and doom and open their eyes, but that would require admitting we have barely begun to scratch at the surface of the causes of climate change. But .. I dont want to derail the current discussion so I will leave you what I’ve been reading, maybe we can discuss that another time.
http://geomag.usgs.gov/downloads/pt2008.pdf
“The second law says only that the NET flow of heat can’t be from the cooler atmosphere to the warmer surface without work.”
Yea, Joel!
Steve,
Great contribution. I’d like to seek clarification if you have time:
As I understand it, the classic greenhouse effect itself represents a feedback process. Namely LW radiation is reflected back to the ground, causing the ground to heat, which in turn radiates more LW radiation. (Part of which in turn is radiated back to the ground, yada yada yada). This of course describes a feedback process.
As I understand it, the dispute is over the feedback associated with the effect of the increase in CO2 on water vapor in the atmosphere, but I think this classic greenhouse gas effect is properly a feedback process too.
Secondly, it is my understanding that simple horizontal-layer models of the Earth’s atmosphere exist, for which numerical computation including cloud effects are possible (using e.g. the large-eddy simulation method). Do you know of anybody who’s actually done a study of the CO2 sensitivity for such models, and if so what is the climate sensitivity of CO2 in such models?
Thanks.