“…ERBE data appear to demonstrate a climate sensitivity of about 0.5°C which is easily distinguished from sensitivities given by models.”
On the determination of climate feedbacks from ERBE data
Richard S. Lindzen and Yong-Sang Choi
Revised on July 14, 2009 for publication to Geophysical Research Letters
Abstract
Climate feedbacks are estimated from fluctuations in the outgoing radiation budget from the latest version of Earth Radiation Budget Experiment (ERBE) nonscanner data. It appears, for the entire tropics, the observed outgoing radiation fluxes increase with the increase in sea surface temperatures (SSTs). The observed behavior of radiation fluxes implies negative feedback processes associated with relatively low climate sensitivity. This is the opposite of the behavior of 11 atmospheric models forced by the same SSTs. Therefore, the models display much higher climate sensitivity than is inferred from ERBE, though it is difficult to pin down such high sensitivities with any precision. Results also show, the feedback in ERBE is mostly from shortwave radiation while the feedback in the models is mostly from longwave radiation. Although such a test does not distinguish the mechanisms, this is important since the inconsistency of climate feedbacks constitutes a very fundamental problem in climate prediction.
Introduction
The purpose of the present note is to inquire whether observations of the earth’s radiation imbalance can be used to infer feedbacks and climate sensitivity. Such an approach has, as we will see, some difficulties, but it appears that they can be overcome. This is important since most current estimates of climate sensitivity are based on global climate model (GCM) results, and these obviously need observational testing.
To see what one particular difficulty is, consider the following conceptual situation:
We instantaneously double CO2. This will cause the characteristic emission level to rise to a colder level with an associated diminution of outgoing longwave radiation (OLR). The resulting radiative imbalance is what is generally referred to as radiative forcing. However, the resulting warming will eventually eliminate the radiative imbalance as the system approaches equilibrium. The actual amount of warming associated with
equilibration as well as the response time will depend on the climate feedbacks in the system. These feedbacks arise from the dependence of radiatively important substances like water vapor (which is a powerful greenhouse gas) and clouds (which are important for both infrared and visible radiation) on the temperature. If the feedbacks are positive, then both the equilibrium warming and the response time will increase; if they are negative, both will decrease. Simple calculations as well as GCM results suggest response times on the order of decades for positive feedbacks and years or less for negative feedbacks [Lindzen and Giannitsis, 1998, and references therein].
The main point of this example is to illustrate that the climate system tends to eliminate radiative imbalances with characteristic response times.
Now, in 2002–2004 several papers noted that there was interdecadal change in the top-of-atmosphere (TOA) radiative balance associated with a warming between the 1980’s and 1990’s [Chen et al., 2002; Wang et al., 2002; Wielicki et al., 2002a, b; Cess and Udelhofen, 2003; Hatzidimitriou et al., 2004; Lin et al., 2004]. Chou and Lindzen [2005] inferred from the interdecadal changes in OLR and temperature that there was a strong negative feedback. However, this result was internally inconsistent since the
persistence of the imbalance over a decade implied a positive feedback. A subsequent correction to the satellite data eliminated much of the decadal variation in the radiative balance [Wong et al., 2006].
However, it also made clear that one could not readily use decadal variability in surface temperature to infer feedbacks from ERBE data. Rather one needs to look at temperature variations that are long compared to the time scales associated with the feedback processes, but short compared to the response time over which the system equilibrates. This is also important so as to unambiguously observe changes in the radiative budget that are responses to fluctuations in SST as opposed to changes in SST resulting from changes in the radiative budget; the latter will occur on the response time of the system. The primary feedbacks involving water vapor and clouds occur on time scales of days [Lindzen et al., 2001; Rodwell and Palmer, 2007], while response times for relatively strong negative feedbacks remain on the order of a year [Lindzen and Giannitsis, 1998, and references therein]. That said, it is evident that, because the system attempts to restore equilibrium, there will be a tendency to underestimate negative feedbacks relative to positive feedbacks that are associated with longer response times.
Concluding Remarks
In Figure 3, we show 3 panels. We see that ERBE and model results differ
substantially. In panels a and b, we evaluate Equation (3) using ΔFlux for only OLR and only SWR. The curves are for the condition assuming no SW feedback and assuming no LW feedback in panels a and b, respectively. In panel a, model results fall on the curve given by Equation (3), because the model average of SW feedbacks is almost zero. In panel b, models with smaller LW feedbacks are closer to the curve for no LW feedback; the model results would lie on the curve assuming positive LW feedback. When in panel c we consider the total flux (i.e., LW + SW), model results do lie on the theoretically expected curve.
Looking at Figure 3, we note several important features:
1) The models display much higher climate sensitivity than is inferred from ERBE.
2) The (negative) feedback in ERBE is mostly from SW while the (positive) feedback in
the models is mostly from OLR.
3) The theoretical relation between ΔF/ΔT and sensitivity is very flat for sensitivities
greater than 2°C. Thus, the data does not readily pin down such sensitivities. This was
the basis for the assertion by Roe and Baker [2007] that determination of climate
sensitivity was almost impossible [Allen and Frame, 2007]. However, this assertion
assumes a large positive feedback.
Indeed, Fig. 3c suggests that models should have a range of sensitivities extending from about 1.5°C to infinite sensitivity (rather than 5°C as commonly asserted), given the presence of spurious positive feedback. However, response time increases with increasing sensitivity [Lindzen and Giannitsis,1998], and models were probably not run sufficiently long to realize their full sensitivity. For sensitivities less than 2°C, the data readily distinguish different sensitivities, and ERBE data appear to demonstrate a climate sensitivity of about 0.5°C which is easily distinguished from sensitivities given by models.
Note that while TOA flux data from ERBE are sufficient to determine feedback factors, this data do not specifically identify mechanisms. Thus, the small OLR feedback from ERBE might represent the absence of any OLR feedback; it might also result from the cancellation of a possible positive water vapor feedback due to increased water vapor
in the upper troposphere [Soden et al., 2005] and a possible negative iris cloud feedback involving reduced upper level cirrus clouds [Lindzen et al., 2001]. With respect to SW feedbacks, it is currently claimed that model SW feedbacks are largely associated with the behavior of low level clouds [Bony et al., 2006, and references therein]. Whether this is the case in nature cannot be determined from ERBE TOA observations.
However,more recent data from CALIOP do offer height resolution, and we are currently studying such data to resolve the issue of what, in fact, is determining SW feedbacks. Finally, it should be noted that our analysis has only considered the tropics. Following Lindzen et al. [2001], allowing for sharing this tropical feedback with neutral higher latitudes could reduce the negative feedback factor by about a factor of two. This would lead to an
equilibrium sensitivity that is 2/3 rather than 1/2 of the non-feedback value. This, of course, is still a small sensitivity.
see the full paper here (PDF)
h/t to Leif Svalgaard
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timetochooseagain: The fact that you can find a paper in the literature that reaches a different conclusion than most of the rest does not mean that the conclusions of all the rest are “totally absurd”. In fact, the paper of Chylek and Lohmann has been heavily critiqued here: http://www.clim-past-discuss.net/4/1319/2008/cpd-4-1319-2008.html I doubt that there are too many people in the scientific community who still believe its result.
And, I don’t understand why you are so dismissive of the paleoclimate evidence (other than because it doesn’t support the conclusion that you favor). Furthermore, Lindzen’s paper is based on an analysis of observational data that I am sure will be critiqued in time by scientists who know more about this than I. Lindzen is probably smart enough that he hasn’t made as obvious a mistake as de Freitas, McLean, and Carter have in their recent paper, but I would be wary of putting too much faith in any new paper that seems to contradict a lot of evidence going the other way.
Paul Linsay (05:53:01) :
“The real question is not warming, it’s why the earth’s surface stays so cool.”
Quite so Paul. I have never understood the AGW argument that ‘global warming’ gases keep us warm and we would be a lot cooler without, as you rightly compare the moons temperature with ours. I overheard someone on the radio talking about fridges using environmentally friendly coolant like CO2 as it is a “natural refrigerant”!
I think the term greenhouse gas is more emotive than descriptive as the actual quality of being able to absorb heat means that cooling is as likely as warming. What I find dishonest is the highlighting of the % increase in CO2 in relation to itself. Meanwhile, if CO2 does reflect all this heat back to the surface, the heat characteristics of the atmosphere that it is part of has changed 1% of 1% of 1%.
The presence of liquid h2o in vast quantities guarantees a rather stable system. Certainly the Earth is not in the uniform unchanging radiative conditions assumed and promoted by the AGW crowd. It’s also key to the very short term negative feedbacks – the h2o vapor cycle and cloud albedo. Cloud fraction (daytime) even determines the necesssary balance T for radiative. It runs about 62% cover and requires an average balance of around 239 w/m^2 to balance the nonreflected incoming power. This 62 % cover is responsible for around 0.22 of the 0.30 nominal albedo while the surface – oceans, land, current glaciers and snow account for only around 0.07 to 0.09. Oceans are what reduces the land albedo so that the surface is significant lower albedo than other bodies, like the Moon.
When you see the supposed effect of a co2 doubling at around 3.7w/m^2 – that’s for clear skies as clouds have significant effects on OLR. If the norm were clear skies, the incoming absorbed power would average more like 311 than 239 w/m^2, requiring a higher T to bring the radiative into balance. Greater cloud cover would result in even higher albedo and less absorbed incoming power which would result in a lower T for balance.
Considering that h2o evaporating absorbs energy, it’s a very light molecule relative to the average (18 vs 29 molecular wt), and it significantly absorbs energy in the IR, it is going to tend to rise up into the atmosphere. As the saturation level is T dependent, it’s going to start to exceed the saturation limits as the altitude increases and surrounding T decreases. It’s also going to radiate quite well – quickly giving off energy that it captures – either by photon absorption, or from higher states due to kinetic interactions with other molecules. It’s going to cool down, become super saturated and form clouds of droplets or ice – giving up that energy used to evaporate it. Typically, it’s going to form more clouds, reducing the incoming solar power and completing the negative feedback loop – without violating the 2nd law of thermo.
Joel Shore (12:23:42) : The Paleoclimate argument starts by saying: Given large CO2 induce climate changes in the past, how can climate sensitivity not be high? But that is looking at it backwards. The proper question should start with observations, saying “given observational evidence for low sensitivity, how can large past changes be attributed to CO2?”-I dismiss the argument because it’s ludicrous-avoiding dealing with the present to blather on about the past that is understood even less.
But I love how “Chylek’s been debunked” (with an argument from numbers!!!) and soon “Lindzen will be debunked”-your faith is truly touching. Let us know when the high priests at RC add a new verse to the Bible you’re thumping.
CO2 cannot change the climate. A desert night with dry air has only CO2 to keep it warm.
It doesn’t succeed!
Desert nights are cold because the CO2 in the atmosphere has no thermal effect. That really should be that.
Sandy (13:56:02) :
“Desert nights are cold because the CO2 in the atmosphere has no thermal effect. ”
It might also be that a desert surface only absorbs heat in the top millimetres of sand. At sunset there may not be much stored heat to lose, and of course the lack of humidity as you say.
Stephen Skinner says
Well, you might try reading up on it then. While the surface of the moon facing the sun may be hot, the other surface is very cold…and the average is well below the average temperature of the earth. This is a good place to start: http://arxiv.org/PS_cache/arxiv/pdf/0802/0802.4324v1.pdf
stored heat – be it desert or ocean only has so much thermal transfer to deal with. Granted that some energy penetrates the ocean more than a mm or two and that convection also exists, but it’s still a matter of just how much heat can be transfered per unit time versus how much it is going to radiate per unit time. We’re sitting on top of a core that is as hot as the surface of the Sun just a few miles below our feet. It’s been that way for billions of years because we’re sitting atop some pretty good insulation in between and there is basically only conduction at work. Just because there’s a temperature difference and hence condution going on, it doesn’t mean that it’s going to have a significant effect as compared with other factors. ultimately, it matters less just how large the thermal sink is than how fast the thermal transfer is in this sort of situation.
Joel shore,
what was the cloud cover like in paleo times and how did that affect the albdeo? When the warming feedback requirements (temperature setpoint) were short circuited by glacial buildups which cut down on surface absorption when cloud cover was less, do you think it required high sensitivity to CO2?
Stephen Skinner (14:12:41) :
“It might also be that a desert surface only absorbs heat in the top millimetres of sand. At sunset there may not be much stored heat to lose, and of course the lack of humidity as you say.”
Interesting. Is the same true over oceans?
Great work, I like the analysis. I would comment though, that the presentation is not to a standard others apply. Richard, if you’re reading this, drop Anthony a line, I can polish up your paper and make it look, well, presentable. The figures should be in-line with the document. I volunteer to be of any help I can to make the document easier to follow. I would be honored to make any contribution I can to help your research and give its conclusions a wider audience.
I also have some interesting ideas on analysis of satellite images and data that might further bolster your claims, more of a near real-time analysis that might make it possible to separate the SW and LW effects on a much shorter time scale. The analysis, taken over time, may provide further insight into the negative feedbacks you are explaining, and should give better understanding of cloud, convection, and storm effects in general. I’ve written a lot of code for image analysis for industrial applications (not vision systems, real home-grown application specific image analysis) and I think I could apply the same techniques to satellite images to discern feedback effects on a shorter time scale… Mike S.
Joel Shore (14:39:09) :
There is a larger range on the moon, thank you Dr. What is it that regulates Earth’s temperature to avoid such a range? Also, why would the climate respond the same way now that it did in the glacial maximum?
Lindzen’s work appears to contradict a recent study of 50 years of low level clouds in the Northeast Pacific Ocean.
http://www.sciencedaily.com/releases/2009/07/090723141812.htm
Strong Evidence That Cloud Changes May Exacerbate Global Warming
ScienceDaily (July 24, 2009)
…low-level stratiform clouds, which currently shield the earth from the sun’s radiation, may dissipate in warming climates, allowing the oceans to further heat up, which would then cause more cloud dissipation.
One key finding in the study is that it is not the warming of the ocean alone that reduces cloudiness — a weakening of the trade winds also appears to play a critical role. All models predict a warming ocean, but if they don’t have the correct relationship between clouds and atmospheric circulation, they won’t produce a realistic cloud response.
Perhaps the low level cloud positive feedback is canceled by the high level cloud negative feedback.
Nice analysis by Lindzen – thank god for more extremely uncommon common sense. Thanks Anthony.
David (14:49:13) :
“Interesting. Is the same true over oceans?”
I wouldn’t have thought so because of the huge heat ‘inertia’ in the oceans. An obvious example are the sub-tropical gardens at Inverewe in Scotland. As I’m sure you know the gardens are possible because of the gulf stream, which has picked heat up from the Carribean and is still warm enough to influence the climate in Western Scotland. Now my experience of sand is that I have burnt my feet on holiday beachs and relief has come by simply getting my feet below the surface, or getting in the sea. In the deserts there are animals that survive by doing the same thing. In addition, come the evening the surface of the sand on the beach will be cool, while surrounding tarmac, brick walls concrete will be radiating stored heat well into the night.
I dont think the assumption that night time desert temperatures are only as a result of cloudless skies. I think it is a combination of very little stored surface heat, and then low atmospheric moisture content and clear skies.
Joel Shore (14:39:09) :
” While the surface of the moon facing the sun may be hot, the other surface is very cold…and the average is well below the average temperature of the earth.”
This is as it should be. The incident radiation flux on the sunward side of the moon is 1360 W/m^2. The incident radiation flux on the dark side of the moon is approximately zero. Outer space is really, really cold, actually at 2.7 K, the leftover radiation from the Big Bang.
You can test this for yourself on a warm night when the air is dry and still. Put a little bit of water at the bottom of a tall thermos bottle and point it at the sky. It will freeze because the incident radiation flux from outer space is much less than the outward radiation from the water, which will turn to ice as a consequence of the radiative imbalance.
Paul Linsay (06:09:15) :
Joel Shore (14:39:09) :
” While the surface of the moon facing the sun may be hot, the other surface is very cold…and the average is well below the average temperature of the earth.”
I’m wondering if an average temperature for the moon is unhelpful. It is either hot or cold and there is no average. Earth on the other hand does have a whole series of average temperatures depending on where you are.
There are a couple of other characteristics used for theoretically calculating earth’s temperature that I think are incomplete or incorrect.
One is Albedo. The highest albedo is of course snow, and the lowest is water. The reason water is the lowest is because it’s very dark. However, I don’t think this is correct as water is clear and it is the absence of light within it’s depths that makes it look dark. Water is highly reflective. Accordingly, forest, bare soil and cities share the same albedo rating, which to my experience is not the case. Any glider pilot will tell you that the best places for thermic lift is built up areas followed by bare soil / farmland. If a glider pilot wants to find thermals the worst place is over forest or water.
The other is calculating the average solar flux as it strikes the Earth as a sphere. Theoretically, if it is as simple as that then having a brick floor exposed to the sun at the equator and a brick wall at the North pole, so solar radiation strikes both at the same angle, will heat both equally. What is missing from attempts to understand and calculate this is the amount of atmosphere the suns radiation has to travel through, which can weaken the effect of the sun considerably.
I may be completely wrong but my experience is telling something different. Of course for hundreds of years it was the common understanding that the Sun went round the Earth, because that is how it looks. But at the same time there were plenty of calculations, models and measurements that showed that the Sun revolves around the Earth.
David says:
Well, I would point to a number of different effects off the top of my head (and I am not sure what their relatively quantitative contribution is):
(1) Having a significant atmosphere period, since the mixing of the atmosphere and its thermal inertia both help to keep the temperatures more uniform.
(2) The greenhouse gases. In fact, I believe Venus has an extremely uniform temperature.
(3) The thermal inertia provided by all of the liquid water…i.e., the oceans.
However, my point of pointing you to Arthur Smith’s paper is that he shows that a planet without IR-active gases in the atmosphere will have an average surface temperature at or below a certain value (its blackbody radiating temperature).
I can’t say I can give you a great answer on this…It would be a good question to ask an expert in the field (rather than just a physicist who reads climate science stuff in his spare time). However, I believe that both the theoretical and empirical evidence suggests that the sensitivity is not going to vary too much over such a range.
The one thing that you could argue could vary most significantly is ice-albedo feedbacks since there was more ice to melt between going from the LGM to now than there would be going from now to a warmer climate. Unfortunately however, the estimate of 3 C per doubling from the LGM to now is derived from considering the ice albedo changes to be a forcing, not a feedback. If you considered them to be a feedback (as they are in our current “experiment” of raising the levels of greenhouse gases), then you get a number more like 6 C per doubling! James Hansen has actually recently been arguing that this 6 C per doubling value may be more realistic although it seems like other scientists such as James Annan are skeptical. (I think the skepticism comes from questioning how fast the ice will melt…and also the issue that I mentioned that it seems like there is less ice that would melt in going from current conditions to a warmer climate than there was going from the LGM to now.)
Paul Linsay says:
Yes…But, my point just is that the average temperature of the moon is lower than the earth and the reason that this is so (despite the fact that the earth has higher albedo) is the presence of greenhouse gases. (Another contributing factor that makes the average temperature even lower than it would otherwise be is the fact that the temperature is so non-uniform since the blackbody bound that I spoke of above is met in the limit of a uniform temperature and the average temperature deviates lower as the temperature becomes more non-uniform. This is because the radiative balance imposes a constraint on , not .)
Anyway, my larger point in all this is that you can’t start talking about the moon and the desert and conclude that CO2 doesn’t have an effect. The relative radiative effects of water vapor and CO2 are well-understood (and, yes, the effect of water vapor is larger but that of CO2 is still significant…even ignoring the fact that without the CO2, it would be colder and hence there would be less water vapor in the air). You are going to find yourself really lonely in the scientific discourse if you choose to try to argue about them. There is more room to argue about the feedbacks, and hence the resulting climate sensitivity as Lindzen does in this latest paper (although, needless to say, his view of such a low sensitivity puts him pretty far out on the edge of the scientific thinking).
On the rare occasions when I’ve been able to locate a graph of the global mean TOA net radiative flux from the satellite data, each has consisted of a neat and hardly varying sinusoidal wave form with a profile which appears, at least to my eye, to be as flat as the Bonneville or Muroc salts. To my, perhaps overly simplistic, view this seems to indicate that the percentage of solar energy being retained by the planet has been essentially constant for the quarter century of the record. To my , again perhaps naive, thinking this should be a direct contradiction of the CO2 theory of global warming which requires that each addition of CO2 to the atmosphere lead to the retention of a greater percentage of solar input. Admittedly, this data set is a bit problematic, but as far as I can tell that criticism is applicable to nearly every data set in the climate field, and if Mr. Hansen and his cohort can use his BS GISS temp data to support their hysterical alarmism I see no reason to exclude contradictory evidence just because it may not be as solid as the Rock of Gibraltar. Of course, I expect that there will be no shortage of commenters who will be willing to explain to me why I’m totally wrong, but we live to learn.
Joel Shore (12:42:01) :
I wouldn’t think it is attributed solely to gases. The moon does get hotter than Earth, so how would heat-trapping gases prevent heat? What about the oceanic effect on climate? I doubt very much that ocean oscillations of today are the same, or maybe not even similar, to the processes present in an ice age. It seems that the evidence points to the oceans as our main climate regulator.
timetochooseagain (17:58:58) :
“Please read the paper.”
Thanks. I have rescanned the paper and agree that the text suggests that the data used incorporate the 2006 Wong altitude adjustments. Previously, I eyeballed the plots for the non-scanner data which appear to be identical to those of a couple of months back. I may need to hunt for a magnifying glass or get some new glasses.
David (14:38:22):
I don’t disagree with you in terms of regulation of the variations in temperature, which is why my post listed the oceanic effects. However, the question as to why the **average** surface temperature more than 30 C higher than what basic physics says ought to be the upper bound for an IR-inactive atmosphere (and the present albedo of the earth) is that it is due to the greenhouse gases, with the biggest contribution coming from water vapor and CO2 being the next most significant contributor.
Joel Shore (12:42:01) :” There is more room to argue about the feedbacks, and hence the resulting climate sensitivity as Lindzen does in this latest paper (although, needless to say, his view of such a low sensitivity puts him pretty far out on the edge of the scientific thinking).”
People who advance science in larger steps usually are “pretty far out on the edge of scientific thinking.”
Joel Shore (17:43:45) :
Actually, your post talked about sea ice, and not oceanic oscillation. It may very well be that greenhouse gases are the largest contributor to our current scenario, but I remain unconvinced. I accept the theoretical possibility that it could happen, but the part I remain unconvinced about is that we can actually override natural processes.
I always think of freak weather events when thinking of climatic shifts, like the tornado outbreak that leveled Xenia, Ohio. It was early for the Pacific Ocean shift, for sure, but could it have been an indicator had we been able to look at it with the technology we now have available? Perhaps such a freak event is the harbinger of a turning point, and perhaps (I really hope not, as I live in OH) it will happen again soon, and be ignored again. Actually, last year we had the leftovers from a hurricane come through and flatten local crops and infrastructure with hurricane force winds, some of us were without power for 2 weeks, and this year we have what can be charitably described as a cool summer so far. And how does the jet stream compare to last year’s?
I know, you will say this is weather, but perhaps not every weather event is so easily written off. I have been through two hurricanes in my lifetime, and what hit us last year in Ohio was definitely the wind from a hurricane, but the rain left the wind behind and visited Chicago for the weekend instead. Freak event, sure. More important, maybe.
Jim (19:40:00) :
Tesla says thank you. Three times. Why three? He was nuts by the account of most who he spoke to.
Paul (14:53:33) :
If you go to the ‘method’ section, p.4, you’ll find:
I can’t help wondering if Lindzen was just stirring by using the uncorrected data in that guest post, or claiming that he was using the uncorrected data. It seems to me that his argument has been based upon the Wong et al. 2006 corrections to that data all along. I could be wrong.
Otherwise, disappointing to see how few comments there are here actually discussing the paper.