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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Petkov-That’s totally illogical. How could it not “matter” if changes were modest and natural? The whole basis of “mitigation” is that changes will be catastrophic and man-made. If those premises are wrong, then the ~only~ approach that makes sense is adaptation!
George E Smith said
“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. ”
I know that the short wave radiation that “tries to heat the surface” does indeed succeed in doing that. At least, for as long as it continues to reach the surface.
However, my question is ‘does the longer wave radiation, emitted from the atmosphere, that “tries to heat the surface” also succeed? If it does, does it succeed in heating the surface at the same time and place that radiation from the surface is heating the atmosphere?
Regarding positive feedbacks:
It is entirely possible to have a system with positive feedbacks, and not have that system go into a “runaway” mode. Such systems are “stable”, but responses to inputs are amplified. In some systems, this is a highly desirable characteristic.
The intuitive response that many have when presented with the notion that some positive feedback causes a signal increase (and that increase in turn causes an increase, and so on) is to assume that any such system must necessarily “go to infinity” or “hit the rail” as was observed earlier.
However, we should rely on mathematics rather than intuition to determine whether this is actually the case.
Let me illustrate with an example. Let’s assume a silly legislature which decides to impose a “financial transaction tax”, and they make it recursively applicable. It’s like a sales tax, but the sales tax is also taxed, and that tax is also taxed, and so on.
This is clearly a positive feedback, but it is not necessarily a RUNAWAY positive feedback. You can have a stable set of values arise out of such a system, where the taxable amount does not grow to infinity. The net effect of such a recursive process is dependent upon the size of the positive amplification effect.
A practical example: If the financial transaction tax rate is set at 20%, it does not drive prices to infinity. If you do the math, it actually increases costs by 25%. Setting it at 80% increases costs by 500%… If you sold a widget for $100, you would owe $500 in recursive taxes at that 80% rate.
As the rate approaches 100%, the “apmlification” effect approaches infinity. At or above a 100% rate, the system will be in “runaway”, and will go to infinity or “hit the rail”. Below that rate, the system is stable but amplified(even if it is grossly unethical), despite the fact that it has positive feedback.
This is the basis for the climate modellers’ “forcings” calculations. They assume that the positive feedbacks are FRACTIONAL… positive feedback, but less than unity. So a given amount of warming is alleged to cause a SMALLER additional amount of warming, which in turn creates an even SMALLER response above that, and so on. Amplified, but not infinite.
None of which is to say that I AGREE with their conclusions… I certainly don’t. But we should be clear as to the meaning of positive feedbacks in this context, and why they do not AUTOMATICALLY make a system inherently unstable. The instability from positive feedbacks (in this context) arises from pushing the response values near (and especially over) a response value of 1.0
Hope this helps.
I’m not sure what puts you in a position to judge my ability to judge the idea. And I don’t know why you think that I just take the pronouncements of a “majority” of scientists on faith-to be properly skeptical is to be skeptical of that, too. I’m not sure what these “many other lines of evidence” are-but I’m not surprised that no tests of the hypothesis seem to have been done. For one thing, there is probably insufficient information from the geological record to test some of the theory’s unique predictions. The Milankovitch hypothesis has been viewed as plausible if not probable for some time, but the data are inadequate to confirm it, and many people will point to apparent problems with it. Does that make it wrong? No, and in fact it probably is right, after all, it makes sense-but do I know that for sure? No, nobody does.
Your logic is reversed. – Anthony
Sigh… inextricably so.
REPLY: Normally that type of criticsm would be warranted, and I understand where you are coming from, but this was an informal essay passed around on an email list as noted in the beginning. His goal was to help many of the laymen and bloggers get a handle on hist ICC09 presentation, which he has succeeded in doing.
[snip BS Phil]
If you want to criticize Linden at peer review level, that’s well and good, but you’ll have to publish your full name and university affiliation here. I grow tired of your criticisms from the cloak of anonymity.
Really, well my criticisms are based on the science not authority so my status and affiliations shouldn’t matter, if you don’t like the argumenrs refute them based on the science, this is supposed to be a science site after all. I note that most of the posters on this thread are anonymous and do not post their affiliations, is this new policy reserved for critics or will you be applying it to everyone?
Step up or shut up. If and when you do, I’ll not only thank and congratulate you, but you’ll also get more respect here. – Anthony
And based on previous experience I will experience malicious spam attacks so I’ll decline to do so. In a scientific debate respect should be accorded to the content rather than the qualifications of its author. Einstein’s papers were accepted in Annalen der Physik because of their content in spite of the fact that their author was a patent clerk with a teaching diploma!
REPLY: Cowardice from possible SPAM, wow that’s a new one! You neglect to point out that your email address does not get revealed here. You want to challenge and attack but only wish to do so from the comfort of anonymity, and I find that cowardly and cheap, like so many of the people that attack from the shadows. – Anthony
Here’s what I don’t get. I know this may be unpopular to some of you, but I do not seriously believe that most AGW scientists are actively evil and purposefully engaged in fraud. Wrong, perhaps. A little too in love with being important and well-funded, perhaps.
Prof L. notes that the models are “tuned” for the results for older periods. Indeed, that’s how you develop/test a model, right? Known beginning point, known end point, give it the beginning point and if it can calculate its way to the end point maybe you’ve got something good going on there.
Well, fine. But if “positive vs negative feedback” is the key crux that everyone seems to agree it is, then what are they doing to their models in those old test periods that still allows them to calculate their way to the known end point? If that’s a whopper they are missing, their must be elsewhere in the model that is making up for it. The equations must still balance as it were. And, frankly, that would be another check to test the validity, or show the invalidity, of their models –there can’t be *one* place they are off, there has to be at least two.
Chris V:
I understand feedback very well indeed, having worked my whole life in electronic and software engineering.
My tax analogy works. What you don’t consider is that any temperature increase or decrease must properly be referenced to absolute zero.
Your ice analogy isn’t very good either because, although less ice does indeed reduce albedo, it also increases heat loss from the ocean at night, besides which, the energy increase necessary to melt ice is of a greater magnitude than the energy decrease necessary to freeze water.
More cloud increases albedo as well as transporting more energy from the surface to the upper atmosphere, suggesting negative feedback to temperature increase, but more cloud also serves to inhibit heat loss at night and, conversely, less cloud allows more heat loss at night, suggesting a positive feedback to temperature decrease.
I should have added: positive feedbacks tend to create a bistable system. Even if the amount of feedback is very small, over long timescales positive feedback to any forcing will tend to move things to one extreme or the other.
timetochooseagain (08:52:25) :
Strangely, I think that a lot of the debaters here may actually be ‘mostly’ in agreement 🙂
Let’s look at the points:
Q. Are ice ages caused by Milankovitch orbital forcing?
A. Yes. The periodicity is too strong a feature to ignore, so Milankovitch orbital forcing is the best explanation.
Q. Do the orbital forcing work by redistributing energy density (temperature)?
A. Yes. This is how is starts. The poles receive less sunlight in the winter when the earth is tilted more and more snow and ice accumulates there in the winter. In the summer the ice reflects sunlight preventing it from fully melting. The results in a positive feedback loop of increasing ice and decreasing albedo. The reduces water vapor and the greenhouse effect … which is another positive feedback loop.
Q. Does positive feedback dominant during an ice-age?
A. Yes. That is why the temperature differences are so large. This can only be explained if there is significant positive feedback occurring during an ice age.
Q. Is this positive feedback larger than 1 … i.e. a run-away greenhouse effect condition?
A. Yes. Coming out of the ice-age we are in a run-away greenhouse effect. As Barry pointed out above. You can have a system with positive feedback that doesn’t ‘run-away’ … after all that is what an ‘amplifier’ is. However in such a system, temperature variability would increase as temperature increased. Also there would be no reason to go into or come out of an ice-age. The temperature would simple bounce around amplifying every random event. You would not get a straight line temperature rise out of an ice-age. Events that were large enough to bring the earth out of an ice-age would result in large overshoot and oscilations due to the long delays in the system and in an inter-glacial period temperatures would be very unstable would bounce around like crazy. Like an amplifier, positive feedback that has not saturated the system will result in ‘amplifying’ any signal. Any minor signal would therefore send temperatures careening in one direction or another and the climate would be extremely variable. The only way there can be stability is if the system reaches saturation OR the positive feedback disappears at the top and is replaced by very strong negative feedback.
Q. Does negative feedback dominate today?
A. Sort-of but not really. This is the main area of contention I think. As mentioned above, in order to get stable temperatues that we have today, we must either be at saturation level of the system, or have a sudden exponentially strong negative feedback kick in within a very narrow temperature range. Saturation will ‘look’ like negative feedback and it is possible to argue that the difference between saturation and a sudden switch to exponentially strong negative feedback is semantics. My opinion of course is that saturation is a simpler concept and doesn’t require a ‘tailor’ made feedback function to ‘exactly’ balance positive feedback that seems quite artificial … but whatever.
Ether:
1. We always have positive feedback and the Earth is just waiting for environment conditions to change beyond a certain threshold to send it careening into a positive-feedback highly-variable glacial stage or a saturated warm and relatively stable stage OR there is a complex.
2. The earth has positive feedback most of the time except at the very top range where there is exponentially increasing negative feedback that suddenly kicks in.
Take your pick .. in the end I think they are probably one and the same (saturation will look like this magically strong and sudden negative feedback)
Geo:
I would suggest that most AGW scientists don’t have their voices heard, much less any misgivings they may have.
Apart from the handful of ‘chiefs’ (Hansen, Mann etc) how many of the other ‘thousands’ have you even heard of?
Barry Kearns (08:50:54) :
Regarding positive feedbacks:
It is entirely possible to have a system with positive feedbacks, and not have that system go into a “runaway” mode. Such systems are “stable”, but responses to inputs are amplified. In some systems, this is a highly desirable characteristic.
Here’s an example that is close to the ghg effect.
Illuminate an grey surface with visible radiation and the temperature will reach an elevated steady state value.
Place a dichroic mirror (which transmits vis and reflects 50% of the IR) this will feedback IR to the surface and heat it up, the system will reach equilibrium when the IR passing through the mirror equals the input.
Therefore Input=100, IR from surface=200, IR from mirror to surface=100, IR though mirror=100.
That is positive feedback and stable.
Increase the feedback by replacing the dichroic with one which reflects 60% of the IR and the feedback increases to 150 so a new higher ss temperature will be reached, you’d only get runaway increase if the mirror reflected 100% of the IR.
Geo,
A stopped clock gives the correct time twice a day. If you can only measure ‘real’ time to an accuracy of, say, plus/minus five minutes, over a ten minute period you could well assume that your clock is correct.
Chris V. (07:30:19) :
If the earths radiation balance is not at equilibrium, the planet must warm or cool until the outgoing radiation equals the incoming.
True, for the statosphere. We happen to live on the surface, and climate happens in the 30 or so kilometers of atmosphere and below, + the oceans. What is true for the startosphere, i.e. energy conservation means also radiative energy conservation, is false below. The metaphysical dictum : “as above so below ” does not hold in the physical world.
Things like convection and evaporation move energy around within the system, but ultimately all energy leaves (and enters) the system in the form of radiation- .
It is the delays and accelerations that are of interest, and the delays do not come from the pitiful percentage of anthropogenic CO2, but from all other factors. The energy transfers that are not watts per m2 are very important, from the PDO and ENSO ( the hot water bottles of the earth) , to evaporationa nd condensation, to the cyclones that move huge masses of air up towards the stratosphere to radiate away their heat content; so your convection does not extend into space! is not really true..
Peter (09:40:56) :
I was not trying to explain the entire climate system in my little ice feedback example- just how climate scientists define a positive feedback. I was just looking at ice in isolation from everything else.
Other posters have complained that climate scientists define positive and negative feedbacks somewhat differently than other in other fields; that may be the source of your confusion.
The way that climate scientists use the terms (including Lindzen in the opening post) is this- If there is an initial temperature change (either up or down) a positive feedback will increase the temperature change, while a negative feedback will reduce it. That’s it!
Anthony could you give any evidence for the veracity of this comment? It is commonly used on this blog, so ther must be siomething?
REPLY: Actually a warmer planet with more C02 will in fact improve growing conditions, which is why that exact growing environment is created in production greenhouses. Your logic is reversed. – Anthony
This may be a true statement for some areas, but it certainly is not for many others already on the edge (I can of course find nothing to back this up in a quick search). If your statement about greenhouses were true then there would be no need to ventilate (for cooling) – this is even necessary in the UK as I found to my cost last year.
There is of course no way crops can mutate to handle the change in temperature – there isn’t time.
I also agree with phil that use of invalid data is not excusable on either side of the debate, and as the owner of a scientific blog I am somewhat taken aback by your comments.
bill,
Maybe this will help: click
geo (09:14:14) :
Prof L. notes that the models are “tuned” for the results for older periods. Indeed, that’s how you develop/test a model, right? Known beginning point, known end point, give it the beginning point and if it can calculate its way to the end point maybe you’ve got something good going on there.
There is a quote that is attributed to Von Neumann, a famous mathematician of the last century :”give me four parameters and I can fit you an elephant, with a fifth it will be waving its trunk”. This to illustrate that not many parameters are necessary to fit a known curve. The climate models have a great multiplicity of parameters that allow for tuning and a good fit.This does not mean that there is a predictive power in the fit. A good example is what has happened with the economy, where risk taking was based on fits to existing data. Existing data did not have the instabilities that lay ahead and foundered the economy.
Well, fine. But if “positive vs negative feedback” is the key crux that everyone seems to agree it is, then what are they doing to their models in those old test periods that still allows them to calculate their way to the known end point? If that’s a whopper they are missing, their must be elsewhere in the model that is making up for it. The equations must still balance as it were. And, frankly, that would be another check to test the validity, or show the invalidity, of their models –there can’t be *one* place they are off, there has to be at least two.
There is not one equation, there are many connected with tunable parameters.
There are two problems with the method in the GCModels as used in the IPCC.
1) Note the purple band around the IPCC temperature predictions. For any other scientific discipline one would think this is an error band, like 1 sigma or such. One would be wrong. This band is a band generated around the initial values of the models perturbed not according to the errors of the contained parameters, but according to the intuitive feelings of the modelers trying to simulate “chaos”. If just one parameter, albedo, were varied within its 1 sigma limit, the purple band would vary by +/- 1C, making a mockery of the plot.
2) There is a more insidious problem. The whole philosophy of the models depends on first order approximations of solutions of very complicated non linear differential equations. Wherever an average value is taken in the grid approximations, the underlying supposition is that the first order term is a good approximation of the true solution. This is not true of this system of coupled differential equations the solutions of which can be highly non linear: after all they give us tornadoes and lightning storms. It is inevitable that the predictive power of the fits will fail after a number of time steps. The weather prediction programs are of similar philosophy and fail after a week or so, needing to be continually retuned. When turned into climate models, the time limits of failure are extended slightly, but failure will mathematically inevitably occur.
Phil. (10:02:45) :
Here’s an example that is close to the ghg effect.
It looks like you actually learned something from the last time you brought this example up (steady state references and that it takes time to get there). Kudos. Just as a check, you do realize that the feedback in your examples are both less than unity, correct (0.5 and 0.6 respectively)?
Mark
anna v-You could also make the statement to geo that it is not unreasonable to say there are two problems with the models given that they are off in way ~more~ than two ways.
http://www.co2science.org/subject/m/modelcharacteris.php
http://www.co2science.org/subject/m/inadeqgeneral.php
http://www.co2science.org/subject/m/inadeqradiation.php
http://www.co2science.org/subject/m/inadeqclouds.php
And so on.
Chris V. (10:35:37) :
The way that climate scientists use the terms (including Lindzen in the opening post) is this- If there is an initial temperature change (either up or down) a positive feedback will increase the temperature change, while a negative feedback will reduce it. That’s it!
Chris, I fully understand this distinction, and this use is incorrect by nearly all climate scientists including Lindzen, Spencer, et al.. The primary “other field” in which this term is used differently just happens to be a) the field in which it was defined (control/system theory) and b) what actually gets used by climate scientists when they create their models (which are mathematical representations with real feedback included in the equations), so they should adjust their usage, and understanding, accordingly.
Mark
bill (10:40:22) :
There is of course no way crops can mutate to handle the change in temperature – there isn’t time.
!!!!
The temperature changes by 15 to 20 C every day/night. There is no need for crops to mutate to handle temperature changes predicted by the IPCC.
It is the other dire predictions ( floods, droughts) that might need adaptation or change of crop type grown, but not temperature. (Not that I believe them)
anna v (10:33:08) :
I did not mean to imply that things like convection don’t effect the earth’s temperature- they certainly do (that’s why early simple climate models – which didn’t include convection- yielded higher CO2 sensitivities than current models).
But my point about the radiation balance (at the top of the atmosphere) is correct- the planet will either warm or cool so that incoming equals outgoing. The exact amount of warming (or cooling) is controlled by other things.
Convection, etc. may carry energy higher up in the atmosphere (where it is easier for the energy to radiate out into space), but ultimately the only way for it to leave the atmosphere is by being radiated out into space.
correction to my anna v (11:00:08) :
The purple band is the measurement errors . The corresponding IPCC curves, were they shown, would have the model dispersions instead of errors. It is the grey bands in the plots below given in Watts per m**2, so I do not know what the 1sigma albedo change for the models would look there, but it should be equally large.
bill (10:40:22) :
Anthony could you give any evidence for the veracity of this comment? It is commonly used on this blog, so ther must be siomething?
REPLY: Actually a warmer planet with more C02 will in fact improve growing conditions, which is why that exact growing environment is created in production greenhouses. Your logic is reversed. – Anthony
The Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) predicts that the Ca increase alone could stimulate terrestrial carbon (C) sequestration by 350–980 Gt (1 Gt ” 1 # 1015 g) C in the 21st Century (Houghton et al. 2001).