Some Comments on the Lindzen and Choi (2009) Feedback Study
by Roy W. Spencer, Ph. D.
I keep getting requests to comment on the recent GRL paper by Lindzen and Choi (2009), who computed how satellite-measured net (solar + infrared) radiation in the tropics varied with surface temperature changes over the 15 year period of record of the Earth Radiation Budget Satellite (ERBS, 1985-1999).
The ERBS satellite carried the Earth Radiation Budget Experiment (ERBE) which provided our first decadal-time scale record of quasi-global changes in absorbed solar and emitted infrared energy. Such measurements are critical to our understanding of feedbacks in the climate system, and thus to any estimates of how the climate system responds to anthropogenic greenhouse gas emissions.
The authors showed that satellite-observed radiation loss by the Earth increased dramatically with warming, often in excess of 6 Watts per sq. meter per degree (6 W m-2 K-1). In stark contrast, all of the computerized climate models they examined did just the opposite, with the atmosphere trapping more radiation with warming rather than releasing more.
The implication of their results was clear: most if not all climate models that predict global warming are far too sensitive, and thus produce far too much warming and associated climate change in response to humanity’s carbon dioxide emissions.
A GOOD METHODOLOGY: FOCUS ON THE LARGEST TEMPERATURE CHANGES
One thing I liked about the authors’ analysis is that they examined only those time periods with the largest temperature changes – whether warming or cooling. There is a good reason why one can expect a more accurate estimate of feedback by just focusing on those large temperature changes, rather than blindly treating all time periods equally. The reason is that feedback is the radiation change RESULTING FROM a temperature change. If there is a radiation change, but no temperature change, then the radiation change obviously cannot be due to feedback. Instead, it would be from some internal variation in cloudiness not caused by feedback.
But it also turns out that a non-feedback radiation change causes a time-lagged temperature change which completely obscures the resulting feedback. In other words, it is not possible to measure the feedback in response to a radiatively induced temperature change that can not be accurately quantified (e.g., from chaotic cloud variations in the system). This is the subject of several of my previous blog postings, and is addressed in detail in our new JGR paper — now in review — entitled, “On the Diagnosis of Radiative Feedbacks in the Presence of Unknown Radiative Forcing”, by Spencer and Braswell).
WHAT DO THE AMIP CLIMATE MODEL RESULTS MEAN?
Now for my main concern. Lindzen and Choi examined the AMIP (Atmospheric Model Intercomparison Project) climate model runs, where the sea surface temperatures (SSTs) were specified, and the model atmosphere was then allowed to respond to the specified surface temperature changes. Energy is not conserved in such model experiments since any atmospheric radiative feedback which develops (e.g. a change in vapor or clouds) is not allowed to then feed-back upon the surface temperature, which is what happens in the real world.
Now, this seems like it might actually be a GOOD thing for estimating feedbacks, since (as just mentioned) most feedbacks are the atmospheric response to surface forcing, not the surface response to atmospheric forcing. But the results I have been getting from the fully coupled ocean-atmosphere (CMIP) model runs that the IPCC depends upon for their global warming predictions do NOT show what Lindzen and Choi found in the AMIP model runs. While the authors found decreases in radiation loss with short-term temperature increases, I find that the CMIP models exhibit an INCREASE in radiative loss with short term warming.
In fact, a radiation increase MUST exist for the climate system to be stable, at least in the long term. Even though some of the CMIP models produce a lot of global warming, all of them are still stable in this regard, with net increases in lost radiation with warming (NOTE: If analyzing the transient CMIP runs where CO2 is increased over long periods of time, one must first remove that radiative forcing in order to see the increase in radiative loss).
So, while I tend to agree with the Lindzen and Choi position that the real climate system is much less sensitive than the IPCC climate models suggest, it is not clear to me that their results actually demonstrate this.
ANOTHER VIEW OF THE ERBE DATA
Since I have been doing similar computations with the CERES satellite data, I decided to do my own analysis of the re-calibrated ERBE data that Lindzen and Choi analyzed. Unfortunately, the ERBE data are rather dicey to analyze because the ERBE satellite orbit repeatedly drifted in and out of the day-night (diurnal) cycle. As a result, the ERBE Team advises that one should only analyze 36-day intervals (or some multiple of 36 days) for data over the deep tropics, while 72-day averages are necessary for the full latitudinal extent of the satellite data (60N to 60S latitude).
Lindzen and Choi instead did some multi-month averaging in an apparent effort to get around this ‘aliasing’ problem, but my analysis suggests that the only way around the problem it is to do just what the ERBE Team recommends: deal with 36 day averages (or even multiples of that) for the tropics; 72 day averages for the 60N to 60S latitude band. So it is not clear to me whether the multi-month averaging actually removed the aliased signal from the satellite data. I tried multi-month averaging, too, but got very noisy results.
Next, since they were dealing with multi-month averages, Lindzen and Choi could use available monthly sea surface temperature datasets. But I needed 36-day averages. So, since we have daily tropospheric temperatures from the MSU/AMSU data, I used our (UAH) lower tropospheric temperatures (LT) instead of surface temperatures. Unfortunately, this further complicates any direct comparisons that might be made between my computations (shown below) and those of Lindzen and Choi.
Finally, rather than picking specific periods where the temperature changes were particularly large, like Lindzen and Choi did, I computed results from ALL time periods, but then sorted the results from the largest temperature changes to the smallest. This allows me to compute and plot cumulative average regression slopes from the largest to the smallest temperature changes, so we can see how the diagnosed feedbacks vary as we add more time intervals with progressively weaker temperature changes.
RESULTS
For the 20N-20S latitude band (same as that analyzed by Lindzen and Choi), and at 36-day averaging time, the following figure shows the diagnosed feedback parameters (linear regression slopes) tend to be in the range of 2 to 4 W m-2 K-1, which is considerably smaller than what Lindzen and Choi found, which were often greater than 6 W m-2 K-1. As mentioned above, the corresponding climate model computations they made had the opposite sign, but as I have pointed out, the CMIP models do not, and the real climate system cannot have a net negative feedback parameter and still be stable.
But since the Lindzen and Choi results were for changes on time scales longer than 36 days, next I computed similar statistics for 108-day averages. Once again we see feedback diagnoses in the range of 2 to 4 W m-2 K-1:
Finally, I extended the time averaging to 180 days (five 36-day periods), which is probably closest to the time averaging that Lindzen and Choi employed. But rather than getting closer to the higher feedback parameter values they found, the result is instead somewhat lower, around 2 W m-2 K-1.
In all of these figures, running (not independent) averages were computed, always separated by the next average by 36 days.
By way of comparison, the IPCC CMIP (coupled ocean-atmosphere) models show long-term feedbacks generally in the range of 1 to 2 W m-2 K-1. So, my ERBE results are not that different from the models. BUT..it should be remembered that: (1) the satellite results here (and those of Lindzen and Choi) are for just the tropics, while the model feedbacks are for global averages; and (2) it has not yet been demonstrated that short-term feedbacks in the real climate system (or in the models) are substantially the same as the long-term feedbacks.
WHAT DOES ALL THIS MEAN?
It is not clear to me just what the Lindzen and Choi results mean in the context of long-term feedbacks (and thus climate sensitivity). I’ve been sitting on the above analysis for weeks since (1) I am not completely comfortable with their averaging of the satellite data, (2) I get such different results for feedback parameters than they got; and (3) it is not clear whether their analysis of AMIP model output really does relate to feedbacks in those models, especially since my analysis (as yet unpublished) of the more realistic CMIP models gives very different results.
Of course, since the above analysis is not peer-reviewed and published, it might be worth no more than what you paid for it. But I predict that Lindzen and Choi will eventually be challenged by other researchers who will do their own analysis of the ERBE data, possibly like that I have outlined above, and then publish conclusions that are quite divergent from the authors’ conclusions.
In any event, I don’t think the question of exactly what feedbacks are exhibited by the ERBE satellite is anywhere close to being settled.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
I guess joel is now speechless concerning my earlier posts as he has now had plenty of time to respond yet has concentrated totally upon more recent posts.
oops. I just read someone write “science doesn’t deal in proof”. Not sure if that was a sarcastic comment.
If not, then that the same as saying that science is the exercise of rhetoric or persuasion?
It would be possible to say that the increase in televisions cause global warming, as the relation between television increase and global temperatures shows a good correlation. This is caused by increasing use of transmission per million of the population”.
If this were questioned, I’d reply “Are you doubting the authority of this obvious correlation? If you are, you’re ridiculous, and I have no time to waste correcting you, since it is so self-evidently obvious”
wattsupwiththat (11:15:40) :
The chief problem for AGW is explaining with verified data how c02 today causes an increase in temperature. C02 intervenes with radiation at very cold places, like Antarctica or the upper troposphere, where it doesn’t have the energy to change the present state of affairs of the climate. The analogy is frying a piece of bacon and arguing that the water from the bacon feeds back into the cooking process to produce a serious risk of burning it. When this doesn’t happen, then it is formulated that the effect must be taking place further up in the kitchen , where it is cooler. I’m sure (I hope) that other have better analogies
cba says:
The honest fact is that I have read what you said a few times now and I still can’t make heads-or-tails regarding what you are trying to say.
No…The geothermal factor is small because the rate of thermal transfer limits the radiative heating that can be supplied to the surface. For the oceans, the radiative imbalance is not determined by the oceans…The oceans merely act as a heat sink delaying the approach to re-establishing radiative balance. I am surprised that you can’t see the difference.
<blockquote
The radiative change you speak of in regards to imbalance is actually a misconception. The simple conceptual models used say that there’s only one mean temperature for the surface given X solar insolation and Y ghg absorption. Even conceptually and simplistically, it’s not right.
I agree with you that, in principle, a spontaneous change in cloud cover could produce a radiative imbalance and that a change in cloud cover in response to a radiative imbalance can provide a feedback. However, there is little evidence to support the hypothesis that significant cloud cover changes occur spontaneously in a sustained way on a global scale…And, furthermore, one would have to suppose that they have occurred with a strong bias in a particular direction…and also that the cloud feedbacks act in a particular direction in response to increases in greenhouse gases (producing a strong negative feedback) in order to explain the lack of response to the known perturbation caused by increasing greenhouse gases. This is a lot to believe in light of quite a bit of evidence to the contrary.
However, in principle, I agree with you that if anything is going to save us from the fate of considerably altering the earth’s climate through our greenhouse gas emissions, it will have to be a strong negative cloud feedback…Because it sure ain’t going to be provided by the sort of nonsense that others here are spouting off about (not believing basic radiative physics or not believing that we are even responsible for the current rise in CO2 levels). If my prejudices pre-disposed me to the “skeptic” point-of-views, as most of the people’s here do, I would focus on providing real evidence of a negative cloud feedback rather than arguing all this other nonsense, which frankly just tells me that some people will believe just about anything in order to avoid truths that they find inconvenient. To their credit, Spencer and Lindzen seem to be taking this route of looking for evidence of such a negative feedback, but their evidence to date isn’t very convincing (and Spencer’s latest argument [ http://wattsupwiththat.com/2009/10/04/spencer-on-finding-a-new-climate-sensitivity-marker/ ] even seems to be that the climate sensitivity is just a tiny bit low of the low end of the IPCC’s 2 to 4.5 C likely range).
Chaos limits predictability in certain ways but not all ways. In particular, it limits predictions that are sensitive to initial conditions. It may make it impossible to believe a detailed weather forecast for a day two weeks hence, but it does not limit our ability to predict that here in Rochester the climate in January is going to be a lot colder than in July.
radiative physics are fascinating (Joel). We’ve gone through the human calorimeter results here:
http://personal.cityu.edu.hk/~bsapplec/heat.htm
underfloor heating has an output of 100w/m2 to produce 24C, at fl0or level though more normally used at 60w/m2.
http://www.energyinst.org.uk/content/files/4g.pdf
At the floor surface, the temperature is 24C, but falls on altitude to 20C at the ceiling, since rising heat cools. This is warmer than the average equivalent temperatures outside. It seems clear to me that an average earth temperature of 15C produces a great deal less energy than 100w/m2
regarding the physical impossibility of c02 heating the surface level of oceans, I don’t see what the fuss is about. If oceans emit heat, and c02 captures a tiny proportion of it, then how exactly does that vastly reduced aerial heat content transmit itself back to oceans, which are already heating cooler air? When you say that oceans are “thermally inert” it means that they have a high heat capacity, whereas air doesn’t have much heat capacity. Oceans can heat air, though the reverse doesn’t count. The Sun can heat oceans – they depend on shortwave prolonged heat. So its the IPCC’s and the NASA’s of this world that strangle thermodynamics by concocting numbers then working backwards to justify them.
so prove otherwise!
Joel,
You’re confusing evidence for man putting CO2 into the atmosphere with evidence that this CO2 is causing warming. Even including evidence suggesting warming is insufficient to establish causality when the expected ‘trends’ are small relative to natural variability..
You’re also confusing Plank distributions of energy with S-B. Even if all of the energy is concentrated in a small band, it can still have an equivalent S-B temperature. Measurements of the surface, including the oceans, indicate that the surface is an almost ideal BB radiator. Once the radiation passes through the atmosphere, there are gaps in the spectrum and the equivalent temperature of the energy leaving the planet is lower. This is the difference between a surface average of 288K and an outgoing radiative average temperature of 255K. You also fail to understand that emissivity, while representing a deviation from ideal BB behavior, is something that can be completely characterized and quantified.
Let me ask you the question I ask all AGW proponents, none of whom has been able to supply an answer.
We can agree that the the additional energy absorbed by the atmosphere from doubling CO2 is about 3.7 W/m^2 (my Hitran simulations give 3.6). Half of this is redirected back to the surface and half is redirected back into space, resulting in 1.85 W/m^2 of additional surface forcing. A 3C increase in average surface temperature requires the surface to emit about 16 W/m^2 more surface power. Whether the resulting energy spectrum is Plank or not, this much surface power much still be emitted. What possible mechanism can provide the gain to amplify 1.85 W/m^2 into 16 w/m^2 (a factor of 8.65)? If you’re hung up on the half/half down aspect, what can amplify 3.7 W/m^2 into 16 W/m^2 (a factor of 4.33), when captured solar power is only amplified by a factor 1.64 (calculate the power ratio between 278.5K and 255K)..
George
There is a great tendency to treat heat as a constant, a fixed currency, in order to balance the books, as though it were a solid. Even a lot of sceptics are taken in by this audacity.
“No…The geothermal factor is small because the rate of thermal transfer limits the radiative heating that can be supplied to the surface. For the oceans, the radiative imbalance is not determined by the oceans…The oceans merely act as a heat sink delaying the approach to re-establishing radiative balance. I am surprised that you can’t see the difference”
Actually, the fact that the oceans have a large delay means that it is quite limited in thermal transfer as well when it comes to the bulk of the oceans. Another difference is that energy can only be injected into the ocean deeper than a few cm by visible light power transfer, not by IR radiative, not by convection, and not by conduction in any meaningful fashion. You’ve still not addressed this – that is the failure of the experiment to take into account the details of energy balance at the surface when it comes to energy flow. Your failure to comprehend it is problematic, perhaps symptomatic.
The experiment you referenced attempted to establish a delta temperature between surface and 5cm below and then to claim that a low differential temperature was evidence that the heat flow was being cut off because the surface temperature – the 5cm temperature was less, resulting in a lower rate of heat transfer.
Given the kitchen physics example of two frying pans simmering on the stove at 350 F where one has a wooden handle and the other has a cast iron handle, which of these has the greater temperature differential and which has the greater heat flow? (and which would you pick up without benefit of an insulating pot holder?)
Concerning the ocean, if you apply conservation of energy in and out of the upper layer, you find that it will radiate/evaporate/conduct energy into the atmosphere based upon its absolute temperature and for radiative it’s going to increase in power output proportional to the 4th power of absolute temperature. Other methods will also increase with temperature, but not to the 4th power. The total energy coming in consists of the incoming IR and convection/conduction from below. Since there is (per your statement) no violation of the 2nd law, there is no net power going from the cooler skin to the warmer lower area. That can only be heated by the incoming solar visible light.
The temperature drop between the 5cm layer and the surface is determined by energy balance of the surface which determines its absolute temperature and by the energy balance at the 5cm point. It is the failure to deliver sufficient power to maintain its absolute temperature which causes that temperature to drop to the point where energy flow is balanced. Only if the temperature differential goes negative with the skin at a higher temperature than lower down will you power flowing down. That was never the case in the author’s experiment.
Even with practically 100 W/m^2 variation in IR coming in, in no case did the skin get close to exceeding the 5cm temperature. That’s over 25 times what a co2 doubling can do. In all cases, the skin temperature had to drop to less than the 5cm mark in order to reach an energy flow balance. It means the capability of that skin to give off excess power is greater than the flow rate of heat from reaching the skin. It also indicates that the variation in this temperature due to ghg forcings is practically nonexistent.
I’ve noticed in some of your posts that there is a problem in your comprehension. When it was brought up that the water evaporation was a powerful conveyor of heat from the surface, you responded that this heat of evaporation never left the atmosphere. While correct in a simple theory sense, it is horribly wrong in the context of the overall system.
That latent heat or heat of evaporation being removed from the ocean surface is substantial on average. It amounts to between 1/3 and 1/2 of the total radiated heat from the surface which leaves the atmosphere. Each gram of water evaporated absorbs far more energy than it takes to heat a gram of water from 0 to 100 deg C. What happens with that vapor is simple, its molecular weight is 18 versus the average of 28.8, meaning moist air is lighter than dry air. Hence it can rise. It also absorbs radiative heat, something not found in climatology 101. Absorbing heat (net) means less density yet so more opportunity to climb in altitude.
If the vapor is absorbing IR based upon a BB temperature distribution of the same temperature – there will be no net absorption or emission. If the vapor is cooler than the heating source, it will absorb more than it emits and if it’s hotter, it will emit radiation lines that are emission lines rather than absorption lines. As the vapor rises, it cools off, becoming a net absorber for sure. That cooling includes conversion to gravitation potential energy, radiation, and conduction. Where water is in the atmosphere and quite a large amount of area beyond that, one has local thermodynamic equilibrium – meaning that the same temperature (locally) is enjoyed by all the molecules in that little area. IE, the ghg radiation absorption is thermalized to the entire gas constituency.
Additionally, that water vapor is now risen to the point where it has become supersaturated and must come out of the vapor phased and become liquid – or even solid. Once aloft, it is above a good deal of the atmosphere and most all of the other water vapor – the major ghg contributor by far. Up there, the vapor is radiating – essentially half outward and half downward – each according to stefan’s law as stefans law is for a solid with a surface radiating outward from that surface. At this point, the radiating lines have a good chance of escaping the atmosphere – but that is not all. Water vapor cannot stay supersaturated forever, it has to drop out of the vapor phase and liquify or become a solid. When that happens, you’re no longer limited to only spectral absorption/emission lines, you’ve got a continuum going. In fact, there is a continuum started when one has dimers (dymers?) – apparently small strings of h2o molecules which create extra modes of vibration which cause non spectral line emissions. The theory isn’t well developed or modeled at present but it does exist somewhat in accord with measurement.
What you wind up with is particulates, and clouds, which radiated in a continuum – even though it is at a lower temperature and hence lower power rate. That though is how your evaporating h2o power transfer at the surface arrives at radiating power away from the planet just like what happens at the surface. Since it is a continuum, it is not blocked completely by higher ghgs, up in the stratosphere.
Convection operates strongest close to the ground where the vast bulk of the absorption takes place. It’s practically nonexistent at the tropopause as there is no need for it there. Actually, it would seem the tropopause is the altitude where that transition occurs.
Since you seem to thing that we are fundamentally out of radiative balance due to measurements, let’s look a bit in that direction. Again, we’re talking the astronomical concept of radiative balance – which includes more than simply radiation as stars have convection zones where the stellar material is completely opaque to radiation present and only convection is occurring there. What it means of course is that while things are not in thermodynamic equilibrium nor are they in perfect instantaneous energy balance, it does mean that conditions are not in the process of changing – like some hidden buildup of energy in the oceans.
Measurements are by necessity done by satellites. There have been claims our average incoming power is 238 or 239 w/m^2 while our outgoing is only 234 or 235 w/m^2. I’m sure you’ll see error bars that are microscopic as well. If you check out the incoming solar, you’ll find SORCE, the most recent satellite shows 1361 w/m^2 and it even has multi stellar calibration capability built in. Theoretical black body caculations and the older satellites indicate solar incoming is about 1367 w/m^2 at mean Earth orbit distance. That’s a half percent error for absolute measurement showing up as a difference between measurements of one parameter of several. Usually, these satellites, which are quite hostile environments for sensitive equipment, often have abreviated measurement approaches such as bands of radiation sensing that then calculate results – not unlike the typical stellar photometry filter measurements being used to determine a star’s surface temperature. In astronomy though, 1-3 % accuracy can be more of a goal than an achievement when it comes to measuring some things.
Given these sorts of things, a less than 2% difference in planetary energy balance, 235 vs 239 w/m^2, is probably well within the real margin of error, regardless of the claims of short error bars that are so pervasive today, especially when related to climatology. The simple fact is that we cannot do a 0.0001% accurate measurement of a whole Earth energy balance and we may not be able to do even an honest 2% measurement either.
george,
the 3.7 w/m^2 or about 3.5 w/m^2 is the outgoing absorption increase – or emission to space at around the 22km nominal tropopause altitude. At 70km, it drops to around 2.7 w/m^2 difference. There is an increase in emissivity due to this increase in absorption but the emission rate at 22km or 70km is not a function of the absorbed power or absorbed power difference. it is a function of the temperature of the air parcel or layer and the emissivity. Increasing the ghg concentrations result in an increase of the emissivity, meaning that the air parcel will radiate more power at the same temperature. what’s more, near the upper edge of the absorbing region – where emissions are much less likely to be absorbed again – we find that increase in emissions will be up and down and that an increase in the emssivity will result in a lower temperature being required for energy to balance. This can be understood by using an arbitrary small unit so that a shell parcel of air increases the ghg content and absorbs an additional 1 unit of power from outgoing radiation. If the parcel’s temperature were the same as the radiation source, then the emissivity increase would be responsible for emitting outbound power by 1 additional unit. Unfortunately, it also has to emit a downward 1 unit of power additional as well. That means we’ve received 1 unit and have to emit 2 units – it’s out of balance and the temperature will have to drop. In the general case, the parcel will absorb 1 unit and have to emit 1/2 unit up and 1/2 unit down additional after the emissivity has been increased. While it’s possible that this might require a temperature increase, it will certainly be much less than a simple S-B calculation that ignores the nature of the emissivity change and the fact that the radiation increases in 2 directions instead of one. Since parcels or layers tend to be rather thin compared with the whole atmosphere, one winds up with absorption and emissions that are far from emissivity = 1.
cba (18:29:45)
“Given the kitchen physics example of two frying pans simmering on the stove at 350 F where one has a wooden handle and the other has a cast iron handle, which of these has the greater temperature differential and which has the greater heat flow? (and which would you pick up without benefit of an insulating pot holder?)”
same “heat flow”, except at the handle, as wood, like air, is a poor conductor. If it were a very dark wood handle, then more, as… let me think… the SB constant says that it absorbs more energy and so emits more..
Sometimes, its necessary to think out of the box
Has anyone else noticed that a 2C increase around a nominal temperature of 288K requires about 11 W/m^2 per the SB equation and that this is exactly the slope of the dFlux/dSST graph in the paper? How about that, theory and measurements actually align!
The slope, indicating net negative feedback, is really the consequence of SST increasing linearly with incident energy (i.e. 1cal/gm per degree C), while radiated energy increases as the 4’th power of temperature. Another prediction of this is that the ratio between the radiated surface energy and the incident solar energy should increases as the incident energy decreases and visa versa.
George
co2isnotevil (George) says:
No I’m not. I’ve been drawn into an argument about whether we are responsible for the increasing CO2 just because some people here are so far out in the weeds that they actually contest this point. In my post of (16:38:07) 10 Nov 2009, I noted clearly that in fact I think it would be wiser for skeptics to focus on arguments about climate sensitivity rather than all of this other nonsense (at least if they are actually interested in convincing scientists and not just confusing the public).
I think there is considerable evidence for at least a moderately high climate sensitivity (e.g., in the 2 to 4.5 C range that the IPCC considers probable) but at least it is not a priori ridiculous to suggest that the sensitivity could be lower, as it is to suggest that we aren’t causing the current rise in CO2 levels or that the greenhouse effect violates the 2nd Law or other such nonsense.
I don’t really disagree with anything you say here except the claim that I am confused about it.
There are a number of mistakes here. First of all, the 3.7 W/m^2 is not the amount of radiation absorbed by doubling CO2, half of which is directed up and half directed down. Rather, it is the change in the amount of radiation emitted at the top of the atmosphere (technically speaking, once the stratosphere has adjusted to the radiative change). So, yes indeed, your division by 2 for the half up / half down aspect is incorrect.
Second of all, since it is a top-of-the-atmosphere value, it is incorrect to compare emission at the surface (at ~288 K). You should be comparing things at the effective radiating temperature of 255K. That will lower your estimate of 16 W/m^2 to about 11 W/m^2.
So, the question is basically how the 3.7 W/m^2 gets increased to 11 W/m^2. And, the answer to that is feedbacks. The most important feedback is the water vapor feedback, i.e., the warming due to the increase in CO2 leads to an increase in water vapor in the atmosphere and that has a radiative effect. (Although closely associated with this is the lapse rate feedback, which is a negative feedback that occurs because the temperature in the upper troposphere is expected to warm more than the surface. This means that the surface does not have to warm as much as the upper troposphere does in order to restore radiative balance. This feedback essentially takes back some fraction of the warming due to the water vapor feedback.) Then there is the ice-albedo feedback due to the fact that the melting of ice reduces the albedo of the earth, causing more solar energy to be absorbed. And, finally, there is the cloud feedback. This feedback is the most uncertain…and this uncertainty is responsible for most of the uncertainty in estimates of the climate sensitivity.
I have no idea how you arrived at the claim that “captured solar power is only amplified by a factor 1.64”.
joel. Since gases don’t have surfaces they radiate in all directions. The most important feedback as you note is water vapour chiefly to its absorbtion range. The second is c02, chiefly too because of its minimal absorbtion range.
translating these figures into temperature we have 0.2C for c02 as a ghg, and that figure is exagerrated to 0.6C by incurring it as an amplifier of water vapour. Since there is no logic to this theory – that only 0.2C can be obtained by c02, it was then coupled with water vapour – the sun’s and PDO’s & ENSO’s completely ignored to make it look like c02 drives the water vapour effect. It is hard to unravel this logic because it is not based on physical logic.
to say top of the atmosphere, (presuming you mean the upper tropopause) then co2 only absorbs at the shoulders – not at peaks, where is crosses with the bands of oxygen & Nitrogen, and there are millions more of these molecules that c02 has to compete with. However, temperature records reveal not 255K but 203K (-70C) or 228K (-45) at the “top of the atmosphere” depending on season and whether at the equator or the poles
addendum: upper troposhere, not upper tropopause at “top of atmosphere”
Joel,
I don’t know about you, but I’ve actually run simulations based on HITRAN_2008 absorption line data and that simulation tells me that the atmosphere absorbs 3.6 more W/m^2 of surface energy when the CO2 concentrations are increased from 280ppm to 560ppm.
Your assertion that the 3.7 W/m^2 represents a reduction in energy leaving the planet is based on the assumption that all energy absorbed by GHG finds it’s way back to the surface and none is re-emitted into space. While I contend this is a flawed and unsubstantiated assumption, it really doesn’t detract from my point since even 16/3.7 is far larger than the gain of the climate system can support.
Your assertion that water vapor feedback amplifies this is incorrect. If water vapor feedback, whose time constant is on the order of days, it at fault, then the net 20 W/m^2 surface difference between aphelion and perihelion should cause a temperature difference of about 16C, which is clearly not evident. Why would water vapor feedback only affect surface forcing resulting from changes in atmospheric heating of the surface and not from changes in solar forcing? If feedback is a response to surface temperatures, then it will apply equally to any change in surface temperature.
To arrive at the 1.63 number is relatively simple. The energy entering the system from the Sun has an equivalent temp of 255K, which represents 239.8 W/m^2. The surface temperature has an average of 288K, which represents a surface power of 390.1 W/m^2. The ratio of these 2 power densities is 390.1/239.8 = 1.63, which represents the power gain of the climate system. Again, if incident energy is amplified by 1.63 at the surface, why would incremental surface forcing originating from atmospheric heating be multiplied by a factor > 4 (actually >8).
Relative to comparing things, temperature is irrelevant. What matters is energy and energy ratios, or more precisely, power density and power density ratios. Moreover, the 16 watts is 16 watts and not 11 watts, as what we are measuring is a change in surface temperature.
I agree that to make a definitive case against AGW, the sensitivity must be quantified. The 1.63 number I presented is the measured climate sensitivity as a ratio of power densities. See this, http://www.palisad.com/co2/eb/eb.html, for more.
George
Joel Shore wrote:
“There are a number of mistakes here. First of all, the 3.7 W/m^2 is not the amount of radiation absorbed by doubling CO2, half of which is directed up and half directed down. Rather, it is the change in the amount of radiation emitted at the top of the atmosphere (technically speaking, once the stratosphere has adjusted to the radiative change). So, yes indeed, your division by 2 for the half up / half down aspect is incorrect.
”
Well, you’re right about there being a number of mistakes there in your’s as well. While you’re right about 3.7 or so W/m^2 being the difference in outgoing radiation, it would seem the where it’s outgoing from is a bit incorrect. I think you’ll find that the 3.7 is outgoing as measured from around 22km above the surface, close to typical tropopause. Measured from 70km, using a typical atmospheric column like US 1976 standard atmosphere, you’ll find it is about a W/m^2 less than the 3.7 at around 22km. You can see this using Archer’s modtran calculator online if you don’t happen to have a one dimensional model up and running. It also only applies to clear skies, and that is less than half the surface at any one time.
“Second of all, since it is a top-of-the-atmosphere value, it is incorrect to compare emission at the surface (at ~288 K). You should be comparing things at the effective radiating temperature of 255K. That will lower your estimate of 16 W/m^2 to about 11 W/m^2.
”
That better not have come from a physics text – or a climatology 101 text either. It’s in gross error. For one thing, the 255k temperature assumes a uniform situation, not half cloud, half surface. If you consider only the clear sky condition, you do not have radiative balance assuming a temperature at the surface of 255k because the cloud half is below 255k in radiative emissions.
What you have for clear skies is 288k along with an absorption of about 30% of the total emissions. That’s about 391 W/m^2 – 120 W/m^2 = ~ 270 W/m^2. That’s roughly 40% of the Earth’s ‘surface’. The rest is emissions from cloud cover which balances out to around 239 W/m^2 overall average and basically, you’re trapping with clouds all that you would have trapped with increased co2 in clear sky conditions.
Taking a surface increase of 3 deg C – to 291 K, you’re up to 407 W/m^2 radiated powerfrom the surface. Since initially one has 120 w/m^2 blocked and ~4w/m^2 added – subtract that from the emitted yields 283 w/m^2 radiated power from the surface – and if you like – subtract out the 3,7 and that leaves 283 w/m^2 rather than the 270. You’ve got around 13 W/m^2 unaccounted for here with the presumption that surface T rises 3 deg C from a no feedback co2 doubling, not 16, not 11.
If one simply works back from what it takes to overcome the change in radiative component, the surface T rise will be just under 1 degree C, excluding feedbacks and convection.
cba,
I have to stand by my 16 W/m^2 number. Whatever forcing is claimed to cause 3C of warming must increase radiated surface energy by about 16 W/m^2, as calculated by (291^4 – 288^4)*5.6704E-8 = 16.5 W/m^2. The point I want to make is that the surface will radiate the same energy at the same temperature, independent of what the atmosphere is doing.
If seems that your value of 13 is really the amount of power that must be added to the system via feedbacks, as all you seem to have done is subtract out the original, 3.7 W/m^2 of forcing power. This sets your baseline ‘unit gain’ to 0, rather than 1, which is more appropriate. You did bring up something that I frequently point out, and which few AGW’ers seem to get, which is that incremental CO2 between clouds and the surface has almost no effect as the clouds are already absorbing most of the surface energy.
In the no feedback case, an incremental watt of forcing increases surface temperatures as specified by SB. Starting at 288K (390.1 W/m^2), 2 more W/m^2 of surface power, 392.1 W/m^2 results from a temperature of 288.37, or a 0.37C increase. If you plot delta power/delta temp for values of temperature around 288K, they fall on the linearized line of the dFlux/dSST plot in Lindzens paper. Actually, a linear fit is not exactly right and it needs to be fit to a T^4 curve instead, but over only a 2C range, the linear approximation is sufficient for illustrative purposes.
George
Presumably, CBA and George, that figure is taken from the SB constant, expressed as 5.67051 x 10-8 x K4.
This equation is irrelevant to climatology and conflicts tenfold with actual recorded energy given off by normal temperature matter, which doesn’t emit that much radiation. In an averagely large room, with different objects this equation says that they shold be emitting at different temperatures. Actual measurements show they equiibriate at room temperature. If radiation were that significant, then they wouldn’t equilibriate: Even the paltry effect of air mlecules over-ride radiation to form an equilibrium. This constant was pulled into climatology to justify the exagerrated numbers required. There are a lot of telemetric results that show it is so far off, though the same results are used in climatology repeatedly without any accountability.
To correct this power of 10, you could divide by 10 and assume that the average energy radiated by earth is 39w/m2.
Underfoor heating produced 100w/m2 to produce 24C at floor level, yet the SB constant produces 390w/m2 at 15C. In the prior case, 100 w/m2 is enough to reach thermal equilibrium for the human rate of 85w/m2 when he not at rest
most heat in the atmosphere gets there as conduction, convection and evaporation, very little by radiation
These AGW absurdities are even embraced by those labelled as sceptics. At -19C 235 w/m2 are emitted. Ice would never freeze if that much energy were being tranferred. At 0C, its 315w/m2 – more than thrice the uniform power of underfloor heating, or else the power of three lightbulbs m2. Water would have to reach -40 before it froze. The fact that it freezes at 0C shows that environmental radiation is not that energetic
P Wilson,
The SB Law is very relevant to climate physics. In fact, what this paper does is show that the climate system behaves according to the SB Law. If you plot power density vs temperature based on the SB law, zoom in to the region at about 288K and normalize the power and temperature to the 288K values, you will get the same deltaFlux vs. deltaSST plot that was extracted from the best fit to the ERBE data.
Relative to your underfloor heating example, you are neglecting 2 important factors. First, is the steradian aspects of the equation. A 100 w/m^2 radiating in a specific direction is equivalent to 400 W/m^2 radiating in all directions. Note that this is also the ratio of the surface area of a sphere to the area of a circle. The other thing you are missing is that the power delivered by the heater is raising the temperature from say, 0C to 24C and not from 0K to 297K.
George
Actually, underfloor heating at the most thermally efficient area where it rises, through insulating effect of screed floors delivers 100w/m2 to the floor surface to produce 24C, which raises temperatures from an ambient 288K to297K.
Joel and I were having a discussion recently about why thermal imaging equipment delivers images of humans against a dark (cool) background, under the assumption that looking at the figures, where 1 met=58w/m2, you obtain 0.7met resting, 2.0-3.4 walking, 1.4-2.6 playing tennis:
These variations aren’t caused by external absorption. They’re caused by human generated activity. The closest to the SB constant is during the course of dancing – up to 8.7met. But for most people a 1.5met would be a good average. the point of this exercise is to demonstrate that increasing the temperatures around the human body, via sunlight or central heating doesn’t increase the wattage of the human body, but attempts to reach an equilibrium with it. When all such fails then its apt to dance or do heavy work to raise the internal wattage to compensate for the lack of equilibrium from the outside. There’s also a cambridge paper on the matter which can be accessed on a google search. Hyper link don’t allow for Cambeidge journals, but can be linked to under ‘Description of a human direct calorimeter’ from a google search.
It was found that at 27C 100wpsm optimum is emitted. That is not because 450 is absorbed, as the SB infers, but what the “human generator” produces, which is relatively warmer than its surrounding objects. NASA assume an human being to be 0.85m2
It brings another anomaly with actual recorded temperatures and temperatures inferred by wavelength sensing. remote sensing infers a temperature at the “top of the atmosphere” at 255k (-18) the confusion here is what is meant by the top of the atmosphere. If it were the top level of the troposphere then actual temperatures are average 208K (-55C). If its the physical top of the atmosphere then its 772K upward
co2isnotevil (15:49:23) :
I agree the trend of the equation is correct. Just that the equation has to be corrected for climatology by a factor of 10, even before the many elusive and other complex factors associated with gases and liquids (air and water) of the climate are taken into account. Some molecular bonds don’t emit heat well, or reduce its ability to emit -increased moecular weight being such a factor
P Wilson,
To raise the temp from 288K (390 W/m^2) to 297K (441 W/m^2), requires adding 51 W/m^2 to the system. In rough terms you can say a 100 W/m^2 heater on half of the time and off the other half can do this. Now, it’s really more complicated than this and there’s the thermal mass of the house, heat loss through insulation, etc. In any event, I don’t see any contradiction here.
People need to be considered as gray bodies, i.e., a black body radiator (at 37C) wrapped in insulation, moreover; this insulation has a relatively low R value which is modulated by activity. When you are very active, your body must radiate away excess heat produced as the result of the chemical reactions driving muscles. It does this by modulating surface blood flow, sweat induced evaporative cooling and other mechanisms that strive to maintain the black body inside at it’s nominal 37C value. The thermal imaging results are all consistent with this.
George
co2isevil and cba: Just to help you out in regards to P Wilson since I have gone around and around with him on this stuff. – His basic confusion is that he doesn’t understand the difference between the NET amount of heat lost by a human and the amount of radiation that would be calculated by the S-B Equation (and measured by an infrared detector). So, he uses results based on calorimetry that suggest that the net heat loss from humans amount to only about 50-100 W/m^2 to conclude that the S-B Equation (for a blackbody) that would imply about 400 W/m^2 emission must be incorrect.
In some sense I can understand the confusion since it is sort of counter-intuitive to imagine that we are constantly bathed in radiation and we just don’t have much experience sitting in interstellar space where there is no significant thermal radiation impinging upon us or air conducting / convecting heat. However, his ability to decide that a cornerstone of modern physics, which is used in technologies ranging from infrared goggles to remote sensing by satellites is incorrect and his poor intuition based on fallacious logic is correct is rather mind-boggling.
REPLY: Joel, Freudian slip? Note first word. – A