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.
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“this is the first articel und WUWT that is disappointing for me. It is not a correct description of the situation.’
I’m afraid I must agree. This is an “Atmospheric Science” paradigmatic presentation.
I’m likely late to the party, but has everyone signed the Global Warming Petition at http://www.oism.org/pproject/ and read the paper there ( http://www.oism.org/pproject/GWReview_OISM300.pdf ) ?
Or even better, has everyone read the paper “Falsi cation Of The Atmospheric CO2 Greenhouse Eff ects Within The Frame Of Physics” by Gerhard Gerlich and Ralf D. Tscheuschner at http://arxiv.org/PS_cache/arxiv/pdf/0707/0707.1161v2.pdf ?
These papers seem to thoroughly debunk anthropogenic global warming by CO2 emissions, unless I’m missing something. I would like to read comments on that second paper, if anyone will comment.
I own a large greenhouse, 28ft wide by 96 ft long by 12 ft high in the center. Please come visit me sometime, and we will go and sit in my greenhouse while you explain your correlation with the Earth’s greenhouse theory.
Can you explain what’s wrong with it?
One commenter noted it didn’t include cosmic rays, convection, precipitation, ocean cycles, etc. This post isn’t about the entire climate system, it’s about the greenhouse effect. Hence, the title “A short primer: The Greenhouse Effect Explained”. It doesn’t claim to be anything else.
Now where does the post go wrong? What is factually incorrect, and why? What’s the correct explanation of the ‘greenhouse’ effect?
Steve Goddard’s tutorial consists of the same old assertions. But you can’t prove a theory by simply repeating its tenets.
Let’s be clear: Electromagnetic energy has no temperature, yet it heats material bodies. So the greenhouse effect is not regarded to trap heat but IS regarded to trap and amplify radiant energy, bringing about the same result. This “trapped radiation” notion harks back to a misconception about glass enclosures, thus the name this theory goes by. It was thought that greenhouses got hot by preventing the exit of “dark radiation.” So radiant energy increased inside the enclosure until it could overpower the glass barrier such that outgoing energy was equal to incoming. Steve’s version is nothing more than a restatement of this fictitious mechanism.
In short, a false belief about greenhouses was the basis of the atmospheric theory — yet the atmospheric theory was RETAINED even after the physics was disproved. Meaning that the atmospheric theory doesn’t have an empirical leg to stand on, no analog in the real world.
The temperature inside a glass house has nothing to do with suppressing the exit of infrared. If solid, IR-reflective glass panes do nothing to amplify thermal radiation within a tight enclosure, however, how much less than nothing do a few swirling gas molecules accomplish in an open atmospheric canopy?
Ric your hyperlink is not working.
Am I getting the message from this thread, that among thoughtful scientific skeptics there is no clearly agreed science of the CO2 GHG efect – somewhat at odds with what Steve Goddard asserts?
What baffles me is, surely the CO2 GHG effect should be testable under lab conditions. A column of pure CO2 equivalent to the CO2 content in the air column naturally – what height would that be? then double it, halve it, wet it, microwave it with different wavelengths, etc. Has this been done? if not why not? Or is this a very naive question?
What about the feedback affect on vegetation?
I understand that if you put more CO2 into the atmosphere, plants grow better. And one of the things that plants can do overtime is to take CO2 out of the atmosphere.
It is one of the ways in which everything is kept in balance.
jae,
What is going on with the humid areas versus arid areas is the rate of absorption and emission of radiation. It is actually the main point of contention between everyone. In a humid area you have a much larger water content in the atmosphere. This requires more time to warm to its maximum temperature since waters absorption rate for heat is 23 times that of air. If you were to look at when a peek temperature occurs in an arid area versus a humid one you would see a time differential as the radiation takes longer to absorb in a humid area versus an arid one ( this would be considering that the atmosphere around the area was static which it isn’t but that is a different issue ) It also explains the rapid decrease in temperature once the sun is no longer as direct for arid zones where as with humid areas it takes longer to then radiate the heat away.
To be honest I think the main problem with the AGW hypothesis is that it says temperatures are going to increase. Technically what should be happening is the long run is that the temperatures should become MORE STABLE instead of the wild swings that we currently have. Much like the temperature in a humid tropic zone does not get too warm during the day or too cold during the night the same should become more true as more Carbon Dioxide, Water Vapor, and Methane are dumped into the Atmosphere.
Of course that probably would not get the same attention as were all going to die unless we so something now. Can you imagine a headline like this, “Earth’s Atmosphere to become more stable through release of greenhouse gases, Film at eleven!”
Plus what incentive is it to change your spending habits, lifestyle, etc. If all that is really going to happen is it will take longer to get warmer in the daytime and longer to cool off at night? If you actually look at most temperature records the increase of temperature is not surprisingly, at night. Which makes sense as it takes a little while longer to radiate that heat back out into space.
Now what a die hard AGW will tell you is everything I have told you is right BUT what is going to happen is that in the morning the temperature from the morning is still going to be warmer then it was the day before and thus cause run away Global warming because the next day it will warm up more and more and more. But we already have a perfect example in Humidity as to the actual effects of this process so I would suggest that this is pure conjecture without any real evidence. Could it happen or be happening… Doubtful, but I am always open to convincing evidence, which I have yet to see myself. Density of the atmosphere and how much radiation hits the planet would have a much more significant impact on the planets temperature then the STABILIZATION power of CO2 or Water Vapor.
@Adolfo Giurfa (07:29:01) :
“Have you experienced a total solar eclipse? Temperature drops inmediately.”
….unless it’s really humid.
And, it gets cold at night. In New England, at the end of Autumn, there were some days when it was in the 90’s, but at night it would go down into the mid 30’s, then back into the 90’s next day. It was also very dry that week.
6:58:33, Steve:
OK, pick some other low-elevation desert. How about Daggett, CA, which has one of the lowest average July humidities of anywhere in the USA at . 24 % RH. The average minimum July temp. is still above Atlanta at 23.3 C. There is certainly no UHI in Daggett!!!
Is this the Steve Goddard who is department chair, computer science and engineering at the University of Nebraska-Lincoln? If so, this is unbelievable.
Deanster and Mary Hinge,
Your points are partially correct. Successive reemissions tend to change the wavelength of the IR, and move into H20 absorption bands. If you assume (perhaps incorrectly) that H20 is fixed, then the effect of increased CO2 diminishes. However, some climate scientists argue that increased CO2 leads to increased atmospheric H2O, thus the need for accurate climate models.
This is not a problem which can be solved qualitatively.
Johnny Honda (03:27:08) :
Why is the day temperature on the moon ca. 160 °C ? No Greenhouse gases!
No gas at all, so temperature as we measure it here on Earth [Stevenson screens, etc] is meaningless. The SURFACE temperature [of the lunar soil] is 160°C.
General: the whole discussion borders on complete chaos, people stating this and that with wild abandon, all claiming it is ‘simple physics’. No amount of factual information can change all these misconceptions. The greenhouse effect is not that CO2 warms up, or that the air around the CO2 warms up, but simply that any energy CO2 absorbs [most of it coming from below] is immediately re-emitted, half up into space and lost and half downwards back to the surface. The surface thus heats up and warms the air by conduction and convection.
If LW radiation is saturated by a short column (3600m) of air containing 350ppm of CO2. A higher density of CO2 say 700ppm will not absorb any more LW radiation and the atmosphere will not get hotter. Energy will be absorbed in a shorter distance (2000m) and heat energy will be mixed by convection. What you say above is not true.
John Galt: see above comment, re: UHI. Look at ANY low elevation desert. Here’s a link: http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/sum2/state.html
“Your comparisons to other cities with the same latitude as Phoenix are also incorrect. Atlanta is not in a desert and does not have the same day-time highs as Phoenix.”
?? What are you trying to say, here?? No, Atlanta is not a desert, and it has three times as much greenhouse gases as Phoenix, yet it’s temperatures (day, night, average) in the summer are lower. Why doesn’t the “greenhouse effect” make Atlanta warmer, especially at night?
As a layperson running a web site on global warming issues, I’m always seeking articles and postings that help novices with the understanding of the complex science involved with the climate. When I saw the headline of this post, I was very hopeful that I would be able to link to it. Unfortunately, after reading it twice, I’ve come to the conclusion it represents a mangled explanation of the greenhouse effect and just continues (increases) the confusion many have on this critical issue. Although your science may be correct, it is poorly explained.
With my last statement, I would recommend a re-write of the post to make it an understandable explanation, with these suggestions:
1. Remove the “feedback” issue from this post and do a Primer #2 on that topic.
2. If you are going to speak about Mars and Venus, put their unique situations in context versus Earth. The way you use them as examples, suggests there is an apple to apple to apple comparison regarding CO2.
3. Drop the “There is no dispute about this in the scientific community” attitude. When I see this, and like-phrases, an immediate B.S. alarm goes off. I especially like your use of this phrase right before you point the reader to a graph that has 3 representations from 3 different studies – the graph tells me there is a scientific dispute. Learn to state to your readers whether something is scientific theory or scientific fact (actual empirical evidence). If it is scientific theory, then it is in a state of “dispute.”
4. In reference to point #3, when you do a re-write, list those points/issues that are scientifically proven. When you are speaking to points that have not been scientifically proven, label them as such. I have great interest in reading your opinions and speculations but don’t mislead by implying certain issues are scientific fact beyond dispute.
5. Don’t ever use the phrase “As Dr. Hansen has correctly argued” or ever refer to him as a means to convince a reader, as it totally undermines any credibility that you are hoping to establish with the reader. It is well understood that he is a political advocate who will manipulate the data and “models” to embellish his arguments. Honestly, how hard would it be to find a reputable scientist and source to make your point?
C3H Editor, http://www.c3headlines.com
@David L. Hagen (07:22:05) :
Nice! Although, in part I think you are only confirming what he said at the end, “If you want to make a knowledgeable argument, learn about the feedbacks. That is where the disagreement lies.” (Even for the Svensmark and Shaviv stuff which aren’t direct actions since their mechanism seems to be more in modulating the “feedbacks.”)
It is getting harder and harder to attribute a significant temperature change to CO2, since there has been no significant increase in temperature for 10-11 years, now. It looks like something else is totally overwhelming any CO2 effects. Oh, maybe it’s the SUN 🙂 See Shaviv’s latest ideas over at Lubos’ site.
MattN (05:53:05) :
BTW, excellent post Steve. The strawman argument that all alarmist use is that we (skeptics/deniers/flat-earthers) do not believe adding CO2 increases temperature when the ENTIRE argument is in the feedbacks.
Have you read through this thread, Matt? It might be a strawman argument if aimed at you, but clearly not so in the case of many others (unless I have imagined all the resistance expressed here to the basics of SG’s article). This is what becomes so bewildering in any of the debates on this site, the fact that anyone expressing scepticism about the prevailing view here is then assailed by a multitude of mutually contradictory arguments. I wish the argument was as you suggest (or mainly at least), but it isn’t so here.
CNN is showing some spectacular shots of the volcano eruption in Chile, looks like a real big bang, now I wonder who is going to tax that?
Anybody who uses the Earth, Mars, Venus analogy when discussing AGW without mentioning the difference in solar radiation these three bodies receives is either ignorant or trying to fool people.
Yet Mr. Goddard thought this argument was so persuasive that it is the fourth sentence in his article.
Johnny Honda (05:04:23) :
And what happened to the LW backradiation to the surface?
It simply warms slightly the surface
Nooo! We must obey the rules of thermodynamics, like Homer. So also the second rule, i.e. no colder matter (atmosphere) can warm a warmer matter (earth).
Correct: The LW backradiation is lessening the net radiation of the surface
You are right, thanks for the correction.
george h. (06:22:56) :
My understanding of the skeptic argument regarding saturation is this: At current CO2 concentrations, all of the available IR in the relevant bands (2.7, 4.3 and 15 µm) is already captured. This is about 8% of the whole IR spectrum, which means that 92% of the IR passes right through without being absorbed by CO2. If the entire atmosphere were composed of nothing but CO2, it would still only be able to absorb 8% of the radiant heat. So if all of the available IR in that spectrum is being captured at current concentrations or lower, then adding more CO2 to the atmosphere won’t matter a bit.
This is fundamentally correct.
Bye,
TMTisFree
This is plain political warming. Did WUWT changed sides?
coaldust (01:12:56) :
You are correct that the geological record contradicts such an outcome, but believe me, it is still taught as a probable outcome on Earth. Here’s a school lecture:
Science Lecture
“The sobering warning for us is obvious: we have to be extremely concerned about processes such as burning of fossil fuels in large volumes that might (we don’t know for sure because the scientific questions are complex) have the potential to trigger a runaway greenhouse effect and produce on the Earth atmospheric conditions such as those found on Venus.”
And many scientists do continue to warn of a likely runaway greenhouse effect on Earth.
Survey Says…
Life doomed by climate woes: Top British scientist
Scientists who back CAGW rarely if ever contradict their brethren who spead fanciful, apocalyptic scenarios, and benefit from scaring the public.
As evidenced by the graph from junkscience.org “Estimating Clear Sky Grenhouse Effect from Quadrupling CO2” there is a wide range of estimates of how large the actual greenhouse effect is. I have read Miskolczi’s paper “Greenhouse effect in semi-transparent planetary atmospheres”. Like kevindick, my most recent course in differential equations is over 20 years in the past, but I couldn’t spot any glaring errors.
The criticisms I’ve seen assert (without support, analysis, or explanation) that Miskolczi mis-applied the virial theorem or Kirchoff’s law, but what they completely fail to attempt to explain is why Eddington’s 1916 solution is better for this application than Miskolczi’s.
Any thoughts?