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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And… Didn’t sensible people already have the suspicion this was true all along anyway? If the “hysterical green house effect”, (as I call it ;), was actually true then there would be an extreme likelihood that a ‘run-away’ climate occurred during earth’s long geologic past, (along with something else major happening to ‘reset’ us back from a Venus-like condition). There is no such indication that anything like that ever happened.
I’ve always been impressed by the data offered by Christopher Scotese
http://www.scotese.com/images/globaltemp.jpg which appears to indicate a natural ceiling to global temperature, (~23C), which is exactly what one would expect from a strong negative feedback. Thank you Dr. Lindzen for scientifically confirming that nature usually makes sense.
It seems “Nature” prefers balance and if feedbacks were positive things would have spun out of control a long time before we came along. As is my nature, I’m being simplistic, but hopefully not simple. =:o
Ooops, I wasn’t piggybacking on Ian Schumacher’s post BTW. What he calls ‘saturation’ could be described as merely a non-linear negative feedback, (like a zener diode in the feedback loop kinda thingy).
Oh dear. Professor Lindzen is being just a little disingenous. He gives us the graphic from Wielicki and Wong, et al, 2002 without mentioning that this paper was the subject of a comment pointing out an alternative interpretation of the disagreements shown between observations and models is that the analyses of the observations may be flawed. and also Another contributing factor to a flawed analysis could be the way the data were processed.
Flawed observations and data analysis. A favourite theme of this very site!
Nor does Prof Lindzen share with us that in 2005 the authors issued a correction to their 2002 paper in which they stated that …
The effects of the altitude correction are to modify the original reported decadal changes in tropical mean (20N to 20S) longwave (LW), shortwave (SW), and net radiation between the 1980s and the 1990s from 3.1/-2.4/-0.7 to 1.6/-3.0/1.4 Wm-2 respectively
That is, the troublesome trend in LW radiation depicted in the graphic was later found to be a near-100% overestimate. As a practicing climate scientist Lindzen must be aware of this, I wonder why he does not mention it in the article, and what effect the correction had on his conclusion of a remarkably low value for climate sensitivity?
>>>Mike Guerin (23:29:36) :
Is it just me? Am I that smart and everyone else that stupid. Isn’t it obvious that for life to exist on earth there must be a strong negative feedback effect in place. Without strong negative feedback does anyone sane really think that the climate on earth would remain stable enough long enough for life to evolve and prosper?<<<
Yes, yes, yes. This has been my thought all along.
If the system was as unstable as their models suggest, then catastrophic cycles would have been triggered too often in the past.
Has anyone asked the modelers what events could eventually reverse a catastrophic warming cycle? Or do they just assume that it’s perpetually irreversible?
Clarification on the following points would be appreciated.
1. Was the following answered
John F. Hultquist (21:30:22)
It isn’t immediately clear why
“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
2. “if one simply doubles the amount of CO2 in the atmosphere, the temperature increase is about 1°C”, and “Climate sensitivity is on the order of 0.3°C”, I then asume the result of doubling CO2 is +0.7°C.
3. Reference the Radiation Anomalies Chart between 1991 and 1992: LW (Red) peaks at approximately -2.5, SW (Blue) peaks at approx +9, NET (Green) peaks at approximately -9. Since (-2.5+9≠ -9), what is NET and does it have any significance in this context?
Roger Knights (05:29:30):
>>>>>But it hasn’t been peer-reviewed, nyah, nyah!<<<<<
Sorry: But,
you have an electric car.
feedback on electric car, nyah,nyah.
Evan: good winds…. and WW II ?????
There is no place for a big or a little or limited greenhouse effect. There is none.
INFRARED IS NOT HEAT RADIATION!!!!
I’m not picking on anyone; certainly not Prof. Lindzen. I greatly appreciate him putting this essay out there to help clarify the debate, and really don’t want to antagonize anyone. However, one quick way to push my (possibly over-sensitive) buttons is to call infrared radiation “heat radiation”. So much so, in fact, that I haven’t even read the whole essay yet. If I seem overly critical of anyone in the rest of this screed, please go back and re-read the first sentence of this paragraph.
Infrared radiation isn’t heat–it’s light. More specifically, it’s electromagnetic radiation that’s just outside the narrow spectrum (visible light) our eyes can respond to.
The reason I think it’s important to keep the two concepts separate is that calling IR heat encourages misconceptions like “carbon dioxide acts as insulation”, or that there can be a mysterious heat sink that is keeping the earth from warming even as our carbon dioxide is trying to warm it. Heat energy is the measure of the kinetic energy of molecules within a body, and IR is electromagnetic radiation, and they are quite different. However, each can cause the other, and therein lies the seed of confusion.
We equate IR with heat for two main reasons. First, elevated temperature is how we normally experience IR. We can’t see IR, but if you put your hand near an electric heating element, the IR radiation is readily absorbed by your hand. At that point, it’s converted to heat, and elevates the temperature of your skin. So you experience the IR as heat.
The second reason we equate the two is IR imaging. Objects near the temperature of the earth (our bodies, rocks, trees, ice, and such) emit IR according to the relationships discovered by Planck, Stefan-Boltzmann, and a whole host of other geniuses I can’t name off the top of my head just now. We can image this IR radiation, and show warmer objects brighter than cooler objects. It’s a convenient shorthand to think of this as thermal imaging, but it’s really not.
One reason this is important is that it makes clear that under the anthropogenic carbon dioxide hypothesis of global warming, the SOURCE of the excess heat is the atmosphere itself. The earth’s surface loses heat by radiating EM energy in the IR wavelength range; the atmosphere absorbs part of this EM through the mechanism of the “greenhouse effect”; that absorption indirectly increases the kinetic energy of the molecules of the atmosphere; and at that moment (and not before) heat is added to the atmosphere, and it’s temp goes up a smidgen.
Looked at from this perspective, it becomes clear that the mysterious “hidden heat sink” that some have postulated to explain why the global temperature is leveling off is particularly silly. If the atmosphere is producing all the extra heat that it must under the hypothesis, it is being transferred to something else as fast or faster than it is being produced. Not only must the heat sink proponents produce evidence of such a sink, they must find a mechanism for transferring all this excess heat from the atmosphere to that sink. That’s a steep hill to climb.
Very very interesting! This article will translate in italian and publish in my site soon…
meanwhille an interestig work with an important grafic by my blog translated by google-translate, so excuse me for english, Simon
http://209.85.129.132/translate_c?hl=it&sl=it&tl=en&u=http://daltonsminima.wordpress.com/2009/03/29/leccezionale-minimo-solare-gia-somiglia-tanto-ai-superminimi-del-passato/&prev=hp&usg=ALkJrhjPC_Q6iSNYz7m_1mc70dTycmHe8A
Degrees kelvin? Oh dear. I still cringe at the memory (decades later) of the bawling out I received when I wrote e.g 255oK. It’s just kelvin – 255K.
It’s nice to see Prof Lindzen’s paper and see the data and model comparisons.
I do have some concerns; and perhaps those concerns relate more to the audience to which Dr Lindzen addressed this paper. He does start out with a heading “Simplified Greenhouse Theory.”
So perhaps available space constrained the amount of detail he includes.
A first concern would be the two terms “long wave” and “short wave”; which would mean different things to a Radio “Ham” I am sure. They don’t mean anything precise to me; so I am going to make a leap of faith and presume, that by “shortwave”, Dr Lindzen means radiation corresponding to the roughly 6000K solar spectrum; and that by “long wave” he means thermal infra-red radiation corresponding to the earth source at 255K (his number) or some other number like 288K corresponding roughly to the alleged mean earth surface or lower troposphere temperature.
If these are not correct assumptions perhaps Dr Lindzen might clarify.
I’m somewhat concerned about lumping the two together in a “net” result; because the detail physics is quite different for those two spectral regions.
I should state here that I am adamantly in total agreement with the final conclusion that Prof Lindzen states; that the current earth climate system is totally regulated by strongly overriding negative feedbacl; a “tipping point” thermal runaway is not possible with the current orbital parameters of the sun/earth system, and the solar constant.
As a physicist (not a meteorologist I look at the problme perhaps a bit differently from Dr Lindzen.
His use of the word “blanketing” is I think quite instructive, because anyone can understand how blankets slow the rate of energy loss from sleeping humans and keep us warmer than we would otherwise be. In the climate case, the delay in exit of the thermal (LW) radiation can be seen as creating a blanket warming, if for no other reason, than the simple fat that during that delay time, the sun keeps on pouring in extra solar spectrum radiation, which will warm things up.
I view the earth’s surface and lower atmosphere warming in a very simple fashion. Two sources of radiation try to heat the surface. The first and most powerful is the solar spectrum radiation from the sun. Most of it propagates some considerable depth in the oceans, to cause local water heating. Some of it is absorbed in the upper atmosphere directly and never reaches the ground; at least as solar spectrum radiation. The other main warming component is the long wave thermal IR emission from the atmosphere itself. This of course is a re-emission of energy which got them from somewhere else, either as direct solar heating, or from surface emitted longwave IR, which is usually thought of as the green house component.
The earth’s surface; particularly the ocean treats the short and long components quite differently; and here my view might not agree with Prof Lindzen’s. As I see it, the long wave returning from the atmosphere is totally absorbed in the top 10 microns or so of the ocean surface or any water on land as well. That must result in very localised warming of the water surface, and lead to rather prompt evaporation of water vapor into the atmosphere. And that isee as a huge energy pump in the form of latent heat of evaportation around 545 cal/gm, which gets carried aloft by the water vapor in convective currents and eventually lost to space from the upper atmosphere. Bottom line is I don’t see any large fraction of that returned long wave energy from the atmosphere being propagated into ocean depths and “Stored” in the ocean. And I also see it as the prime source of the water vapor feedback that ultimately leads to precipitation and the obligatory extra clouds that come with precipitation; and that I see as the direct source of Dr Lindzen’s negative feedback; and although the details may be more complex, it seems to me that the mechanism isirrefutable; specially in light of the paper of Wentz et al in SCIENCE July 7 2007; “How Much more Rain will Global Warming bring?”
As to the fate of the solar spectrum energy propagated into the ocean many metres; the depth of propagation is like the solar spectrum turned upside down; the highest intensity spectral components in the blue green region going deepest, and the red and violet ends being attenuated at shallower depths.
From there I don’t see any powerful mechanisms form moving this energy significantly deeper, to store it in the deep oceans. There will of coursae be conduction in all directions; but since ordinary sea water always has a positive temperature coefficient of expansion down to its freezing temperature, there must be upward convection currents established by the solar energy warming, so the deposited solar energy must in my view be inexorably transported back towards the surface, and since convection almost always trumps conduction; I don’t see a deep ocean energy storage mechanism, other thqan what ocean circulations might be set up by the local georgraphy.
Anyhow, I’m skeptical that there is much of a downward flow of energy into the ocean; I think it is largely returned to the surface over time,a nd ultimately lost to the atmosphere or space, by surface radiation (nearly black body) and conduction or evaporation.
As to the component of the long and short wave radiations captured by the atmosphere, it is clear from absorption spectroscopy that water vapor is a significant absorber of solar spectrum radiation and CO2 is not, and as for the long wave, water vapor once again absorbs over a much larger spectral range than CO2, so a doubling of CO2 is really just a drop in the bucket of increased green house absorption, since the atmosphere doesn’t really care which molecular spoecies captured the IR photon and conveyed the energy to ordinary atmospheric gases in collisions.
So to me the concept of “climate sensitivity” is simply a red herring. Any immediate surface warming due to a CO2 increase, sets in motion the evaporation/cloud formation/precipitation feedback which is always strongly negative.
As I have said many times; nobody ever observed it to warm up when a cloud passes in front of the sun; it always cools in the shadow zone; and the fact that last night it remained a little warmer overnight because of some high cloud cover, is irrelevent. It still cooled down after sunset; and in any case, that was last night’s weather; not climate.
I would hope that Prof Lindzen would take advantage of sites like WUWT to educate more of us in this arcane subject matter.
George
Another Mike D (22:39:57) : I think that the main temperature difference between Venus and us isn’t the difference in energy coming from the sun, it’s the surface pressure. I live in Chinook country on the Eastern slope of the rockies I can vouch for a 30 degree centigrade temperature change over about 6 hours when the chinook kicks in (quick version: air cooled over the mountains follows down the mountain slopes, pushes up against valley air and forces compression.
I think it is heating because of the compression — IOW: the change in pressure. Look up adiabatic process.
John Philip,
How odd that Dr. Lindzen failed to cite every critique of his references.
Unlike Hansen and Schmidt who always present a balanced view and diligently refer to every criticism of their work and citations.
Re: alexjc38 (06:08:29) :
“How does the Eocene warming episode of 55 million years ago (PETM) fit into this? I often see it mentioned as an example of positive feedback at work.”
Not sure what other have written here on the Eocene, but there was more than just atmosphere/ocean effects at work during the Eocene.
What we know about the Eocene is this
1) Just before the Eocene, the Indian plate drifted North and ran smack into Asia forming the early Himalyas.
2) The Eocene then started with one of the most extreme rises in temperature known in the geologic record and is correlated with a sharp extinction event which removed a lot of the prior Paleocene fuana. What caused the warming? Unclear – the forming of the Himalyas would have most certainly generated a massive change in the global circulation pattern. CO2 outgassing from this event could have reinforced warming, but a dramatic change in the surface topography of the Earth has to be player!
3) The temperature gradient between polar regions and equatorial regions during the Eocene was half what it is today with the polar regions much warmer – temperate forests extended right to the poles during the Eocene. Eocene Palm Trees have been found in Alaska and Swamp Cypress on Elsemere island in the Artic for example. The recent finding of a fossil snake the size of a school bus in Columbia also extends from this period.
4) Other factors at play are that a) at the beginning of the Eocene, Australia and Antartica were still a connected super continent (warm equatorial currents able to mix with colder Antartic waters easier than they can today), and b) Europe, Greenland and North America were still part of one supercontinent at the start of the period.
5) By late in the Eocene, both these supercontinents had split and the Mediterranean had formed.
6) There was then another extinction event late in the Eocene – which is correlated with 2 major impact events – one over Siberia and the other in the Chesapeake Bay . This extinction is known as the Grande Coupure or “Great Break” which is also associated with a major turnover in fauna and the arrival of the first Europeans from Asia.
The bottom line is – I don’t think you can attribute changes in Climate during the Eocene (particularly early in the period) to the same feedbacks in the atmosphere/ocean that we are talking about here. There were dramatic geologic changes during this period.
John Philip (07:37:24) :
I can’t tell from the graph whether Lindzen used the old figures or the revised ones. He does reference 4 other papers on the same data so I’m inclined to think he’s got current figures.
But how can you tell?
“”” Ian Schumacher (06:52:07) :
anna v (23:08:24) :
“Would you say that the negative feedback shown by the data here is the beginning of an ice age? :). ”
My personal opinion is that most of the observed warming is an illusion (not real and simply due to measurement error). The temperature changes we are dealing with here are smaller than the measurement error. “””
Ian, where did you get the idea that negative feedback ends ice ages. I don’t think ice ages are something that happens from a slight imbalance in the climate. Major changes of orbit parameters and the like or solar changes create and eventually end ice ages; not some minor weather shift.
As to the “switching” from positive to negative feedback; it is quite elementary.
Water vapor which is far and away the only greenhouse gas of any significance at all, creates positive feedback warming by absorbing lots of earth emitted long wave IR. It also has some negative feedback component since it also absorbs incoming solar radiation, which reduces the ground level insolation (and warms the upper atmosphere; which then radiates to space). But water vapor in the atmosphere eventually leads to both liquid and solid water in the form of clouds; no other GHG does that; and clouds reflect incoming solar radiation back into space (albedo effect),a nd then they block further solar radiation from reaching the ground; thereby cooling the surface. The shadow zone formed by a cloud is ALWAYS cooler than outside the shadow zone.
So water exhibits both positive and negative feedback depending on the phases present. At any time, total global cloud cover is around 50% If it warms up (for any reason) you get more evaporation from the ocean, which must be balanced eventually by more precipitation,a nd that means more clouds blocking more sunlight so it gets cooler.
If it gets too cool, you get more precipitation, leading to less cloud cover, so more sunlight reaches the ground, and it warms bacl up.
How difficult is that to understand. So long as the earth has its oceans we could neither raise nor lower the temperature by any significant amount; even if we wanted to.
George
Ivan (05:49:40) :
But, what we are really interested in is overall net feedback (SW plus LW), not just LW. I believed it is also negative and Lindzen says so, but looking at the graphs he presented show that SW feedback is stronlgy positive as well as overall feedback which is also on positive side (3rd panel). Is there anything I don’t understand correctly?
During the ‘inadvertent experiment’ described by Lindzen he shows a sharp increase in LW associated with a sharp rise in temperature but no corresponding increase in SW (so no increase in tropical clouds).
Where the models apparently go wrong is that they produce more clouds in the tropics in response to warming whereas the data suggests that they should not.
Apart from the obvious point that if the climate was dominated by strong negative feedback how did the sharp rise in temperature occur, the analysis is flawed in another way.
From the ERBE website:
“In general, the absorbed solar radiation exceeds the outgoing longwave radiation in the tropical and subtropical regions, resulting in a net radiative heating of the planet, while in the middle to polar latitudes there is a net cooling. This equator-to-pole difference, or gradient, in radiative heating is the primary mechanism that drives the atmospheric and oceanic circulations. On an annual and long-term basis in which no energy storage and no change in the global mean temperature occurs, this radiative imbalance between the tropics and polar regions must be balanced by meridional heat transport by the atmosphere and oceans.”
So Lindzen is demolishing a strawman, a system where LW losses from the tropics are balanced by SW input to the tropics. However, the input in the tropics is balanced by LW from the whole planet due to the aforementioned meridional flows. So in order to do this type of analysis he needs the data from the whole planet. So nice try but no cigar!
Robert Bateman (03:36:25) :
If I am getting all of this correct: The satellites measured the shortwave coming from the Sun, and the longwave being lost by the Earth, and found equilibrium.
No, the satellites are measuring both SW and LW from the earth. The sun’s radiation is relatively constant. The relation between temperature, outgoing LW and outgoing SW radiation is basis of this thread.
Re: Eocene Warming
“CO2 outgassing from this event could have reinforced warming…”
To clarify- the standard theory is that there was first a massive outgassing of circa 1400-2800 Giga tons of methane from oceanic clathrates during this period (likely due to the collision and subuction of the Indian Plate under Asia) which then led to massive carbonate dissolution in marine sediments which then released CO2.
Again, very different to what have seen over the past several 100 years…
Graeme Rodaughan (22:45:14) :
“It’s the Evidence guys….”
Thank you for giving Dr. Lindzen’s work such a clear, honest perspective. There are indeed much bigger issues to address than the now thoroughly falsified AGW theory.
Exactly the same thought came to my mind and I was going to say so but checked the comments to see if anyone else had noticed it.
This is EXACTLY what Dr. Spencer has been saying … the observations do not match the models. He made the case here back in December and I believe he is close to submission of a new paper on the subject.
Ian Schumacher (06:52:07) :
Another consideration is that if we switched from positive to negative feedback coming out of an ice age we should see this as ‘overshoot’ and oscillations.
I do not know about overshoot, but certainly at the flat top there are oscillations:
http://en.wikipedia.org/wiki/File:Vostok-ice-core-petit.png
particularly in the holocene.
http://upload.wikimedia.org/wikipedia/commons/c/ca/Holocene_Temperature_Variations.png
I hope by oscillations you use the generic term and not a “harmonic oscillator” expectation.
So of course there are negative feedbacks. The most important one iw albedo changes. Try the toy model :http://junkscience.com/Greenhouse/Earth_temp.html
by changing the albedo.
Ian: The latest on NPR was an interview with this lady who stated that there really isn’t anything they can do about runaway AGW, but that they will do as much as they can. As much as they can to throw whatever they can under the Bus to slow it down. This is the cry I am hearing now. It’s too late, but they will go down fighting.
The unstable node distrubed, massive boulder plunges down slope to sleepy village below.
anna v (08:41:15) :
So of course there are negative feedbacks. The most important one iw albedo changes.
In the context of ice ages, albedo is mainly a function of the extent of ice cover, and it is a POSITIVE feedback, not negative.
Warming results in less ice cover; less ice cover means lower albedo; lower albedo means more sunlight is absorbed, which translates into more warming.