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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Clear, concise and to the point. Well written article and (as with many other recent findings) should help in putting a check on the insanity bandwagon that we are on currently.
Thank you Dr Lindzen and Anthony – keep up the good work, and most importantly keep the light of objective science burning…
There’s a typo beneath “The Results of an Inadvertent Test”:
“so the should not expected”
should be “so they should not be expected”
A somewhat open minded BBC radio interview with Roger Harrabin (he who capitulated to the demands of eco-campaigner Jo Abbess) and Vicky Pope. You might want to run this one as a new blog entry, Anthony
Around the 10 minute mark the presenter displays some scepticism.
http://news.bbc.co.uk/today/hi/today/newsid_7936000/7936645.stm
As a result, the radio show presenter has been rapped by the Ends Report and John Vidal of the Guardian for being open minded
http://www.guardian.co.uk/environment/blog/2009/mar/31/james-naughtie-ends-report-climate-scepticism
This has been bothering me for a while: I’m a controls engineer, modeling of physical systems [very simple ones compared to the atmosphere] is most of what I do.
There is no such thing as a stable system who’s behavior is dominated by positive feedbacks. That’s pretty much the definition of positive feedback. Yet the AGW theory, as I understand it, maintains that Earth’s temperature was fairly stable until sometime in the industrial age, then started warming due largely to positive feedback on temperature. Obviously something else is going on, as there must have been some mechanism that stabilized temperature in the past.
Furthermore, if you did have a system that was somehow balanced on an unstable node, and you disturbed it, it would fall away from that node. Removing whatever disturbed it wouldn’t return it to the node, it wouldn’t even stop the system moving away from it (you can’t un-disturb the system). In other words, if world temperature were dominated by positive feedback, and CO2 did disturb the precarious balance, even if we completely halted CO2 emissions, that wouldn’t stop the runaway warming. ANY disturbance of a positive feedback system is a “tipping point.”
“Excellent, first class. A calm look at reality is what is always needed.”
But it hasn’t been peer-reviewed, nyah, nyah!
And it’s by a middle-aged white male!!
with ties to the Heartland Institute!!!
Case closed.
There are some problems in this analysis.
1. The Radiative Anomalies in the y-axis isn’t defined.
2. The author states, “the observations characteristically exceed 7 times the model values” but doesn’t explain how he arrived at this conclusion. The graph shows only one data point above or near 7 which is not sufficient data to make the claim.
3. The author then seems to use this one data point to make the conclusions in the paragraph titled, Bottom Line.
How did the climate modelers ignore the data from this experiment?
It was specifically designed to confirm or modify the very, very basic designs/theory surrounding the models – the greenhouse effect itself.
How come we haven’t heard about this before? They must have decided to bury it when it didn’t confirm the theory/models but actually said they needed to go back to the drawing board.
It is almost like (it is exactly like) any data which does not conform to their view is ignored, discredited through various strawman arguments or subsequently changed afterward.
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?
Mike Guerin (23:29:36) :
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?
Jack Hughes (01:31:30) :
If there was positive feedback, then the climate would be unstable – and would have been de-stabilised by now with disastrous consequences.
The sign of the feedback coefficient does not indiciate stability or instability. Feedback can be positive and produce a stable system. Feedback can be negative and produce an unstable system.
Fortunately, it appears that in the earth climate system vapor+cloud feedbacks are net negative and stable.
Thank you Anthony and Dr. Lindzen. Through this blog I am getting the semantics to piece together what has been intuitively obvious. If our climate was unstable as the AGWers want us to believe, we would not be having this discussion. When mass extinctions have happened via extraterrestrial impacts or volcanoes, there surely was enough biomass to generate ‘greenhouse’ gases in excess of anything we produce. To the best of our knowledge, CO2 has been in the 5-6000ppm range without a runaway system, and without climate being much warmer. This means as others pointed out above, there is an upper limit to climate temperature. This has to be, lacking a major fluctuation from the only local heat source, the sun.
Our importance is highly over-exaggerated, and as regards climate, there is nothing new under the sun. It appears we are at or near maxium temperature for this planet, so we need to appreciate it while we can. As pointed out by others here, warm is better than cold. The hysterics over runaway heating is silly on the one hand, and just another a political ploy on the other. Many in the illusory position of power remain there by playing on the ego-centric nature of humans that is extrapolated to the near omnipotent effect our presence must have on our environment. This is exaggerated too by the false sense of esteem bestowed on the past generation or two via reward for nonachievement through our education and welfare systems. Herein lies a runaway system effect, false fear in the masses = money and power for the elite.
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:
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.”
Not sure what your point was.
–Mike Ramsey
Excellent article – but I have a question. If the Earth’s climate is dominated by negative feedbacks, 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.
Biased CBC reporting (read it all).
Fire. Them. All.
Notice CBC attempts to deflect the reader by using words e.g. “Pricey ads”, etc.
Fire. Them. All.
…-
“Pricey ads signed by scientists slam Obama’s climate change talk
More than 100 scientists — including a number of Canadian government scientists and university professors — have signed a full-page newspaper ad denouncing U.S. President Barack Obama’s remarks about climate change last November as “untrue.”
“The Cato Institute ad takes issue with the following statement, made by U.S. President Barack Obama on Nov. 19, 2008:
“Few challenges facing America and the world are more urgent than combating climate change. The science is beyond dispute and the facts are clear.”
“Mr. President , your characterization of the scientific facts regarding climate change and the degree of certainty informing the scientific debate is simply incorrect,” said the ads paid for by the Cato Institute that ran Monday in the New York Times, the Washington Post, the Washington Times, the Chicago Tribune and the Los Angeles Times. The ads cite evidence, referenced in four scientific papers, that the climate is not changing significantly.”
“Among the Canadians who signed the ad were:
* Ian Clark, professor of Earth Sciences, University of Ottawa.
* Paul Copper, Laurentian University (Emeritus).
* Susan Crockford, University of Victoria.
* Christopher Essex, University of Western Ontario.
* Neil Hutton, past president, Canadian Society of Petroleum Geologists.
* Wayne Goodfellow, University of Ottawa.
* David Nowell, former chairman, NATO Meteorology Canada.
* Peter Salonius, Canadian Forest Service.
* Ross McKitrick, University of Guelph.”
http://www.cbc.ca/technology/story/2009/03/30/tech-090330-cato-climate-change.html
http://www.smalldeadanimals.com/archives/011105.html
Ian W,
It is quite possible to prevent a runaway in a system with net positive feedbacks, since it can be modelled as a converging power series.
Ian W (05:27:50) :
You are absolutely right. For a kiln or an oven to work properly you need insolation, our planet´s insolation it is not the atmosphere but sea water.
In this “post modern” theory it seems that you can keep it warm just with the atmosphere inside the kiln!! It seems somebody is postulating an infinite atmosphere!, like having infinite covers on a bed!
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?”
Ivan, perhaps the SW increase is cause by increased cloud cover. Again reducing the effect of greenhouse gases and lowering temperature.
Thank you , Dr. Lindzen. I have been following your work for over a decade. You have suffered the slings and barbs of those who disagree. You should be revered for your courage alone, never mind the incredibly sound science. I am well aware of the mud that has been (is being) thrown at those who question the science of a Co2 driven climate. Now that you have thoroughly destroyed the Co2 theory, what are your thoughts on what is actually driving our climate? Dr. Svalgaard, who posts here says that it isn’t the sun ( oversimplified for expedition). I would certainly like to hear your theories. Any possibility? Thank you in advance, …………… David Ball
If the climate sensitivity is only around 0.3 degrees, how do we get ice ages?
Comparing temperatures during the last glacial maximum to today yields a climate sensitivity of about 3 degrees +/- a degree or so (basically the same as the models get).
If the climate sensitivity is only 0.3 degrees, that implies that there is some HUGE completely unidentified forcing responsible for taking us into and out of ice ages. That could be, but it seems unlikely to me.
Is there a way to link directly to this paper or to get a pdf?
“Eloquence is logic on fire.”
To believe AGW, you must believe that 380 PPM CO2 becomes an atmosphere-covering sheet of one-way mirror.
Those shoes just ain’t a pair – the right one is shiny and pointier, the left one is rounder and dull. I suggest the owner gets his eyes tested before he drives again.
That looks like a really old car too. Who knows. Though I haven’t driven an automatic (except for rentals) in over 20 years. I suspect Europeans drive automatics as much as Americans or anyone else. 😉
I was thinking he’d need to get his brakes replaced quite often. And adding a lot of particulate pollution with those quickly-wearing brakes…
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.
So unfortunately I think the negative feedback is also probably an illusion. changes are so small relative to noise that this allows everyone to see what they want to see.
I believe we always have positive feedback, BUT we have reached saturation, which can look like negative feedback.
I would invite people to take a close look at the shape of temperature changes coming out of an ice age. Look at the slope. If negative feedback was responsible for ending ice ages the transition from warming to stable temperatures should occur gradually. Instead, temperature increases steadily at basically a constant rate and then sudden becomes a flat top. That is ‘clipping’, i.e. hitting a hard limit.
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. There is a fairly large delay in negative feedback mechanism. A delay should cause overshoot and oscillation behaviour to be observed, not a sudden clipping, that we actually see — that has to be because of saturation. We never stop having positive feedback, however the system hits the maximum value … saturation, a hard limit. At least that is my theory 😉
Someone above said what I’ve always found amusingly paradoxical about the Gaia hypothesis-namely that it sounds like it speaks of negative feedbacks! Well, the key here is that in order to get into Lovelock’s mind set, you must see humans as inherently separate from nature-negative feedbacks apply to nature, and if we aren’t a part of nature, negative feedbacks can’t protect nature from us. Ridiculous, I know, but Lovelock’s idea makes no sense.
As for the Paleocene-Eocene Thermal Max, mention above, there is a brief discussion here, featuring me:
http://www.globalwarmingskeptics.info/phpbb3/viewtopic.php?f=5&t=343
Very nice argument and clearly presented, thank you Dr. Lindzen. However, it seems to me there is a basic flaw: it is assumed that the LW emission is a function of temperature, only – including a feed-back, of course -but this is not necessarily the case. The cloud cover can change for many reasons, natural variability, cosmic ray intensity etc, and clouds provide an important part of the greenhouse effect. So the LW radiation does not necessarily respond just to the temperature change. In fact, the decrease in cloud cover that gives increased SW energy input (reduced albedo) will also increase the LW output.
Instead, this dramatic change of cloud cover over a short period (10 y) demonstrates that clouds are not a passive system, responding in a well defined way to gradual warming, but a complex dynamic system with other driving forces. And the associated climate forcing is very large, dwarfing at least on this time scale the small effect of increased CO2 concentration.