NEW 4/10/09: There is an update to this post, see below the “read the rest of this entry” – Anthony
Guest Post by Richard Lindzen, PhD.
Alfred P. Sloan Professor of Meteorology, Department of Earth, Atmospheric and Planetary Science, MIT
This essay is from an email list that I subscribe to. Dr. Lindzen has sent this along as an addendum to his address made at ICCC 2009 in New York City. I present it here for consideration. – Anthony
Simplified Greenhouse Theory
The wavelength of visible light corresponds to the temperature of the sun’s surface (ca 6000oK). The wavelength of the heat radiation corresponds to the temperature of the earth’s atmosphere at the level from which the radiation is emitted (ca 255oK). When the earth is in equilibrium with the sun, the absorbed visible light is balanced by the emitted heat radiation.
The basic idea is that the atmosphere is roughly transparent to visible light, but, due to the presence of greenhouse substances like water vapor, clouds, and (to a much lesser extent) CO2 (which all absorb heat radiation, and hence inhibit the cooling emission), the earth is warmer than it would be in the absence of such gases.
The Perturbed Greenhouse
If one adds greenhouse gases to the atmosphere, one is adding to the ‘blanket’ that is inhibiting the emission of heat radiation (also commonly referred to as infrared radiation or long wave radiation). This causes the temperature of the earth to increase until equilibrium with the sun is reestablished.
For example, if one simply doubles the amount of CO2 in the atmosphere, the temperature increase is about 1°C.
If, however, water vapor and clouds respond to the increase in temperature in such a manner as to further enhance the ‘blanketing,’ then we have what is called a positive feedback, and the temperature needed to reestablish equilibrium will be increased. In the climate GCMs (General Circulation Models) referred to by the IPCC (the UN’s Intergovernmental Panel on Climate Change), this new temperature ranges from roughly 1.5°C to 5°C.
The equilibrium response to a doubling of CO2 (including the effects of feedbacks) is commonly referred to as the climate sensitivity.
Two Important Points
1. Equilibration takes time.
2. The feedbacks are responses to temperature – not to CO2 increases per se.
The time it takes depends primarily on the climate sensitivity, and the rapidity with which heat is transported down into the ocean. Both higher sensitivity and more rapid mixing lead to longer times. For the models referred to by the IPCC, this time is on the order of decades.
This all leads to a crucial observational test of feedbacks!
The Test: Preliminaries
Note that, in addition to any long term trends that may be present, temperature fluctuates on shorter time scales ranging from years to decades.
Such fluctuations are associated with the internal dynamics of the ocean- atmosphere system. Examples include the El Nino – Southern Oscillation, the Pacific Decadal Oscillation, etc.
These fluctuations must excite the feedback mechanisms that we have just described.
The Test
1. Run the models with the observed sea surface temperatures as boundary conditions.
2. Use the models to calculate the heat radiation emitted to space.
3. Use satellites to measure the heat radiation actually emitted by the earth.
When temperature fluctuations lead to warmer temperatures, emitted heat radiation should increase, but positive feedbacks should inhibit these emissions by virtue of the enhanced ‘blanketing.’ Given the model climate sensitivities, this ‘blanketing’ should typically reduce the emissions by a factor of about 2 or 3 from what one would see in the absence of feedbacks. If the satellite data confirms the calculated emissions, then this would constitute solid evidence that the model feedbacks are correct.
The Results of an Inadvertent Test
Above graph:
Comparison of the observed broadband LW and SW flux anomalies for the tropics with climate model simulations using observed SST records. The models are not given volcanic aerosols, so the should not expected to show the Mt. Pinatubo eruption effects in mid-1991 through mid-1993. The dashed line shows the mean of all five models, and the gray band shows the total rnage of model anomalies (maximum to minimum).
It is the topmost panel for long wave (LW) emission that we want.
Let us examine the top figure a bit more closely.
From 1985 until 1989 the models and observations are more or less the same – they have, in fact, been tuned to be so. However, with the warming after 1989, the observations characteristically exceed 7 times the model values. Recall that if the observations were only 2-3 times what the models produce, it would correspond to no feedback. What we see is much more than this – implying strong negative feedback. Note that the ups and downs of both the observations and the model (forced by observed sea surface temperature) follow the ups and downs of temperature (not shown).
Note that these results were sufficiently surprising that they were confirmed by at least 4 other groups:
Chen, J., B.E. Carlson, and A.D. Del Genio, 2002: Evidence for strengthening of the tropical general circulation in the 1990s. Science, 295, 838-841.
Cess, R.D. and P.M. Udelhofen, 2003: Climate change during 1985–1999: Cloud interactions determined from satellite measurements. Geophys. Res. Ltrs., 30, No. 1, 1019, doi:10.1029/2002GL016128.
Hatzidimitriou, D., I. Vardavas, K. G. Pavlakis, N. Hatzianastassiou, C. Matsoukas, and E. Drakakis (2004) On the decadal increase in the tropical mean outgoing longwave radiation for the period 1984–2000. Atmos. Chem. Phys., 4, 1419–1425.
Clement, A.C. and B. Soden (2005) The sensitivity of the tropical-mean radiation budget. J. Clim., 18, 3189-3203.
The preceding authors did not dwell on the profound implications of these results – they had not intended a test of model feedbacks! Rather, they mostly emphasized that the differences had to arise from cloud behavior (a well acknowledged weakness of current models). However, as noted by Chou and Lindzen (2005, Comments on “Examination of the Decadal Tropical Mean ERBS Nonscanner Radiation Data for the Iris Hypothesis”, J. Climate, 18, 2123-2127), the results imply a strong negative feedback regardless of what one attributes this to.
The Bottom Line
The earth’s climate (in contrast to the climate in current climate GCMs) is dominated by a strong net negative feedback. Climate sensitivity is on the order of 0.3°C, and such warming as may arise from increasing greenhouse gases will be indistinguishable from the fluctuations in climate that occur naturally from processes internal to the climate system itself.
An aside on Feedbacks
Here is an easily appreciated example of positive and negative feedback. In your car, the gas and brake pedals act as negative feedbacks to reduce speed when you are going too fast and increase it when you are going too slow. If someone were to reverse the position of the pedals without informing you, then they would act as positive feedbacks: increasing your speed when you are going too fast, and slowing you down when you are going too slow.
Alarming climate predictions depend critically on the fact that models have large positive feedbacks. The crucial question is whether nature actually behaves this way? The answer, as we have just seen, is unambiguously no.
UPDATE: There are some suggestions (in comments) that the graph has issues of orbital decay affecting the nonscanner instrument’s field of view. I’ve sent a request off to Dr. Lindzen for clarification. – Anthony
UPDATE2: While I have not yet heard from Dr. Lindzen (it has only been 3 hours as of this writing) commenter “wmanny” found this below, apparently written by Lindzen to address the issue:
“Recently, Wong et al (Wong, Wielicki et al, 2006, Reexamination of the Observed Decadal Variability of the Earth Radiation Budget Using Altitude-Corrected ERBE/ERBS Nonscanner WFOV Data, J. Clim., 19, 4028-4040) have reassessed their data to reduce the magnitude of the anomaly, but the remaining anomaly still represents a substantial negative feedback, and there is reason to question the new adjustments.”
I found the text above to match “wmanny’s” comment in a presentation given by Lindzen to Colgate University on 7/11/2008 which you can see here as a PDF:
http://portaldata.colgate.edu/imagegallerywww/3503/ImageGallery/LindzenLectureBeyondModels.pdf
– Anthony
UPDATE3: I received this email today (4/10) from Dr. Lindzen. My sincere thanks for his response.
Dear Anthony,
The paper was sent out for comments, and the comments (even those from “realclimate”) are appreciated. In fact, the reduction of the difference in OLR between the 80’s and 90’s due to orbital decay seems to me to be largely correct. However, the reduction in Wong, Wielicki et al (2006) of the difference in the spikes of OLR between observations and models cannot be attributed to orbital decay, and seem to me to be questionable. Nevertheless, the differences that remain still imply negative feedbacks. We are proceeding to redo the analysis of satellite data in order to better understand what went into these analyses. The matter of net differences between the 80’s and 90’s is an interesting question. Given enough time, the radiative balance is reestablished and the anomalies can be wiped out. The time it takes for this to happen depends on climate sensitivity with adjustments occurring more rapidly when sensitivity is less. However, for the spikes, the time scales are short enough to preclude adjustment except for very low sensitivity.
That said, it has become standard in climate science that data in contradiction to alarmism is inevitably ‘corrected’ to bring it closer to alarming models. None of us would argue that this data is perfect, and the corrections are often plausible. What is implausible is that the ‘corrections’ should always bring the data closer to models.
Best wishes,
Dick
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Peter (13:03:30) :
Have you not considered that clouds may be a negative feedback acting against temperature increases, but not temperature decreases?
That is physically impossible.
Mike Ramsey (06:02:21) :
Your sarcasm detector is malfunctioning 😉
DaveE
kevin: here’s another paper to read. But it will cause much howling, hissing, and gnashing of teeth, if presented to certain people (who think they are much smarter 🙂 ).
http://www.geocities.com/atmosco2/atmos.htm
I am not sure it is correct either, but I have not seen it disproved (at least to my satisfaction).
I am certainly no expert on this subject, either. But I cannot find anyone who IS for sure?? There are plenty of experts out there, including PhD physicists, who laugh at the “atmospheric greenhouse effect.” Their arguments keep me wondering if it really exists. I tend to think it is bullshit, but as I said, I’m no expert….
Chris V., how about addressing my response to your claims instead of the easy pickings?
You cannot simultaneously assert that the Earth’s climate system presently has strong positive feedback on temperature and that the Earth’s temperature is naturally stable absent anthropogenic CO2. The positive feedback on temperature would insure that any temperature changes from whatever source would be amplified until you hit the rail at which the source for the feedback is exhausted.
If you design a circuit with positive feedback, for example, a small voltage increase or decrease will cause the voltage to rapidly hit the upper or lower rail, whichever direction the voltage is going. Hitting the rail means that the circuit no longer has the power supply to push the voltage higher or lower than it’s current state.
Positive feedback in the Earth’s climate should work in the same manner. Look at ice extent as an example. As temperatures increase, ice melts and thereby exposes the underlying surface which absorbs more radiation. But the ice extent decreases which means that the available feedback supply has been reduced. At the point where you are just coming out of an ice age, the potential feedback effect from reducing ice extent is very large – but when you are well into the interglacial, that supply for warming feedback has pretty much exhausted itself, being limited to only polar regions and very isolated mountainous areas. At the same time, the potential positive cooling feedback has been increasing such that, when the Earth’s climate moves back past the equilibrium point towards an ice age, there’s lots of land area that can potentially be covered by ice – tending to increase the speed at whch the climate cools back to the ice age.
Every other positive feedback effect will work in the same manner – it’s simply a fact of existence. Positive feedback in a given direction starts out strong, and consumes itself as rapidly as it’s able until you reach a point where you just cant’t move much further in that direction. At the same time, potential feedback in the opposite direction strengthens.
If you look at the climate record, there is very good evidence of positive feedbacks in the sense that the Earth’s climate rapidly moves into and out of ice ages, but then stays in that state (either ice age or interglacial) for a period of time much longer than the transition time from one to ther other. But the Earth’s climate system itself will exhaust the positive feedbacks during the transition period, after which you have reached the rail – i.e. the stable portion of the ice age/intergalcial that exists until you have a net input in the other direction.
Since we seem to be towards the end of the existing intergalcial, I think it’s absurd to suggest that the Earth’s climate system still has the potential to supply a large positive warming feedback. Quite the opposite – we should be at the point where there are large reserves of cooling feedback sources such that, when the earth does swing back to the negative energy balance phase, those cooling feedbacks will tend to rapidly (on a relative scale) cause glaciation.
Jack Simmons (00:43:18) :
Isn’t this amazing, as the temperature goes up, negative feedback goes up. As the temperature goes down, the feedback starts going positive.
What is even more amazing we can describe it with one word,
Entropy
Lindzen is debunked http://www.realclimate.org/index.php/archives/2007/04/lindzen-in-newsweek/
and the rest of MIT seems to disagree…
http://madrad2002.wordpress.com/2009/03/12/mit-do-you-want-to-gamble-here/
Mike Guerin (23:29:36) : “Is it just me?
Nice to see so many agreeing with you.
Roger Knights, excellent idea this betting… for skeptics, Piers Corbyn is the man I think.
Prof Lindzen, such a cool cool touch to use models to end the models. I luuuuuurve it.
However, I would love to hear your responses to John Philip (despite Steve Goddard’s well-aimed riposte, and my dislike of JP’s language style) and Phil. My experience is that AGW’s get me to really polish and perfect my material, so they have a good function 😎 They end up helping me prove the skeptics science twice as well 😀
Phil. (08:20:31) :
“So Lindzen is demolishing a strawman”
Demanding Lindzen’s argument demonstrate the radiative balance of the entire planet is a red herring, a distraction.
Lindzen isn’t concerning himself with radiative balance as such. He is showing via the study there is a negative feedback affecting LW radiation IN the tropics where the temperatures are the highest. The radiation doesn’t care where the atmosphere or the oceans transport any warmth next. It can all travel to timbuktu or oshkosh.
The models expect a reduction in the escaping radiation due to positive (greenhouse) feedback as the temperatures rise. The higher the temperature the less LW radiation should escape the earth EVEN IN THE TROPICS. But the opposite is the case and by quite a bit.
He calculated the climate sensitivity from this information. If you want to attempt to demonstrate that climate sensitivity changes depending on where you plant your feet, go ahead. But supposedly CO2 is well-mixed and anyway the highest water vapor content occurs in the tropics.
I’ll leave the radiative balance of the entire planet to Spencer.
Mike Guerin (23:29:36) : Is it just me? Nice to see so many here share your feeling.
Roger Knights, nice idea to bet on stuff.
Prof Lindzen, really really cool to use models to end models.
But I’d also like to hear your response to the two warmist posters here who challenged your science. My experience is that warmists really sharpen my wits and get my proof TWICE as strong in the end.
Chris V. (13:52:19) :
That is physically impossible.
Actually, your understanding of feedback is incorrect. If a feedback subtracts from the input, i.e., if the feedback is negative, then it will subtract from the input whether it is trending up or down. In other words, feedback is dependent upon its own sign, not the input signal.
Mark
Matt Dernoga-Oh I’m so scared-the obfuscators in chief at RC have “rebutted” Lindzen’s arguments and, gasp, the got a bunch of smart guys to side with them! Well, they must be right! [snip]
Reply: Let’s raise the bar people, no name calling ~ charles the moderator
Moderator-That’s not a name, its not even a noun, its an adjective. If you’re gonna snip me, get the grammar of my crime right. It was, however, a cheap insult. For that I apologize.
Reply: You are correct it was an adjective, but I don’t recommend calling me on my grammar when you use “its” for it is (twice!), and the first word I snipped was “your” for you are. ~ charles the erring yet contrite grammar nazi moderator.
Matt Dernoga (14:50:37) :
Lindzen is debunked http://www.realclimate.org/index.php/archives/2007/04/lindzen-in-newsweek/
Hardly a “debunking” from 2 years ago… Using the Hockey Stick to “prove” any point is rather ridiculous. That Mann and Schmidt (and the rest of the Team) stick to their proven flawed methodology is rather humorous. I also find it interesting they use an agreement between models and reconstructions as evidence their claim is correct. They, of course, conclude with the tired ad hominem “Lindzen is funded by big oil” refutation. Give it a rest.
and the rest of MIT seems to disagree…
http://madrad2002.wordpress.com/2009/03/12/mit-do-you-want-to-gamble-here/
Hardly “the rest of MIT.”
Nice try.
timetochooseagain (15:14:06) :
No need to sling ad hominems from the skeptic side, his argument is sufficiently pathetic to prove the point you’re intent on making.
Mark
“Mark T (15:01:31) :
Actually, your understanding of feedback is incorrect. If a feedback subtracts from the input, i.e., if the feedback is negative, then it will subtract from the input whether it is trending up or down.”
Actually Chris V. agrees with your point. He stated that it was impossible for a situation where negative feedback applied in the warming direction but not in the cooling direction. I’m not sure that I would categorically rule out that possibility, however. Certainly it would be unusual, and offhand I can’t think of any natural mechanism that would dampen temperature increases but not dampen temperature decreases, or vice versa, but it’s plausible that you could engineer that effect.
The italics should have ended after the Newsweek link, and begun again at and the rest of MIT seems to disagree.
How about some of that auto-quote stuff like over at CA, Anthony? 🙂
Mark
Ouch. Your right! My grammar ~is~ bad! I blame the speed of electronic communication…
Mark T-Heat O’ the moment as they say-RC generally sets off my “AGH!” meter, which triggers irrational rant mode, which is followed by polite discussion and understanding.
kurt (15:27:30) :
Actually Chris V. agrees with your point. He stated that it was impossible for a situation where negative feedback applied in the warming direction but not in the cooling direction.
I disagree. I think that is what the original post said, and Chris V disagreed. Perhaps he, or I, misread the original post, but this:
may be a negative feedback acting against temperature increases, but not temperature decreases?
seems to be exactly what you just said, and Chris V disagreed with.
Mark
Syl (11:27:54) :
“re feedbacks
As I understand it before each glaciation started the Arctic may have been ice free (and sea levels were higher than today). The warmists always warn us that an ice free Arctic will mean less albedo and further warming due to this positive feedback. I think the opposite occurs–negative feedback. Less ice means more ocean cooling. In fact I think this may have been a causitive factor (or I could be all wet) in the cold cold winter we had after the ‘unprecedented melt off’ of Arctic ice a couple of years ago.”
that is a very interesting view.
all the warm water transported to the arctiv can lose it’s energy much quicker without ice cover.
I’m with Ed Fix, George E. Smith and Kevin. I welcome the post by Prof. Lindzen and his courageous opposition to AGW alarmism. But I disagree with his physics of the planet atmosphere effect, the so-called ‘greenhouse effect’.
The blanket analogy is an improvement but is still misleading. A blanket prevents convection; it does absorb and radiate energy. Prof. Lindzen’s post will soon join the list of failed explanations of ‘the greenhouse’ effect in this document, by Gerlich and Tscheuschner.
http://arxiv.org/abs/0707.1161v4
From a physics view it is the average properties that matter, especially density. All the molecules of the air are quite similar. H2O, O2, N2, CO2 and CH4.
Is the Earth emitting radation at 255K? I see the average global temperature given as 13oC, that is 286K.
Appeasing the AGW alarmists by accepting to debate on their terms, greenhouse, forcings, feedbacks and sensitivity is futile.
If someone mentions a greenhouse or a blanket to me I insist they explain how CO2 does it before go further. I soon mention convection. Most AGW alarmists know little or no physics. So it is quickly clear that we are having a political and not a scientific discussion.
Roger Knights (12:43:40) :
Mike Ramsey (06:02:21) wrote:
Roger Knights (05:29:30) :
“Excellent, first class. A calm look at reality is what is always needed.”
But it hasn’t been peer-reviewed, nyah, nyah!
“Note that these results were sufficiently surprising that they were confirmed by at least 4 other groups:”
Including a bibliography doesn’t make a paper peer-reviewed. This paper was presented at ICCC and e-mailed to Anthony–that’s all, so far. (AFAIK)
I was referring to the fact that four cited papers were published in peer reviewed journals.
Mike Ramsey continued:
Not sure what your point was.”
I was parodying a typical Insister response to Lindzen. I could have included “/sarc]” at the end, but that sort of nudge in the ribs spoils the joke.
I suspected but was not sure that you were being ironic which was why I added the above. All good fun.
–Mike Ramsey
Manfred-How exactly would less ice make the oceans lose heat more easily? The ice albedo feedback is actually one of the more convincing, simple, elegant feedbacks-at least in a qualitative sense. Water is less reflective than ice, so it absorbs more light, heating it up, melting more ice, and so on. Are you and Syl suggesting that ice “traps” heat below the surface? How’s that supposed to work?
Roger Clague-Oh really?
http://eaps.mit.edu/faculty/lindzen/198_greenhouse.pdf
timetochooseagain (15:50:16) :
“How exactly would less ice make the oceans lose heat more easily?”
the water temperature in the arctic ocean is higher than the atmosphere’s temperature for most time of the year. heat should should then flow from the water to the atmosphere. the idea is, that ice cover shields the warm water from the cold atmosphere and also from enhancing transport mechanism such as wind.