In preparing for my climate presentation in Phoenix next week, I went back and read through Lindzen & Choi, a study whose results I linked here. The study claims to have measured feedback, and have found feedback to temperature changes in the natural climate system to be negative –opposite of the assumption of strong positive feedback in climate models. I found this interesting, as we often do of studies that confirm our own hypotheses.
Re-reading the study, I was uncomfortable with the methodology, but figured I was missing something. Specifically, I didn’t understand how an increase in temperature could result in a decrease in outgoing radiation, as Lindzen says is assumed in all the models. As I have always understood it, the opposite has to be true in a stable system. With an added forcing, temperature increases which increases outgoing radiation until the radiation budget is back in balance. Models that assumed otherwise would have near infinite temepratures. I assumed perhaps that Lindzen & Choi were making measurements during the time the system came back into equilibrium.
Apparently, both Luboš Motl and Roy Spencer have spotted problems as well, and they explain the issue in a more sophisticated way here and here.
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.
Spencer further makes the point he has made for a couple of years now that feedback is really, really, really hard to measure, because it is so easy to confuse cause and effect.
Spencer by the way points out this admission from the Fourth IPCC report:
“A number of diagnostic tests have been proposed…but few of them have been applied to a majority of the models currently in use. Moreover, it is not yet clear which tests are critical for constraining future projections (of warming). Consequently, a set of model metrics that might be used to narrow the range of plausible climate change feedbacks and climate sensitivity has yet to be developed.”
This is kind of amazing, in effect saying “we have no idea what the feedbacks are or how to measure them, but lacking any knowlege, we are going to consistently and universally assume very high positive feedbacks with feedback factors > 0.7”
AFAICT, ‘they’ are postulating that the feedback is also non-linear. It wouldn’t really kick in until some kind of tripping point is reached.
Such systems are not unknown. Parametric amplifiers can be made to oscillate. Given a black box, such systems are very hard to analyze even if you are sitting at a bench with all the test equipment you could ever want.
When we look at a long time scale, it looks like the earth has some kind of oscillation as the earth bangs in and out of the ice ages. It looks like a clipped oscillation similar to an electronic oscillator banging back and forth between ground and the supply voltage. In that regard it appears that there is a limit to the earth’s maximum and minimum temperatures.
On a smaller time scale, it is very important that the medieval warm period was hotter than it is now. It means that we are nowhere near any tipping point where the system becomes unstable and starts rapidly warming.
Note that skeptics reviewed a very plausible, credible report and did true peer review, inspite of its skeptical-favoring conclusions.
Contrast this with the approach given to the hockey sticks and other bad work from AGW promoters.
I was wondering if the same review also looked at the 4 papers that Lindzen purports to show the same results.
Indeed others have noted the potential inconsistencies and Dr. Lindzen himself has said on Wattsupwiththat.com that the work would be redone, but I have never been clear whether the supporting papers are affected by the same problem.
Either way, the point about feedback likely being a low number, positive or negative, is interesting especially given IPCC climate model assumptions.
Another related question I had was with regard to the Vostok ice core data: one thing that’s always struck me is that the CO2 rises lag temperature.
The reason for this seems fine: that warmer temperatures cause the oceans to release more CO2.
However, if CO2 is either a straight warming or if CO2 is a multiplicative warming factor, then it seems odd that temperature would peak before CO2.
I would think that for any type of positive CO2 contribution, that temperatures would at least coincide with the CO2 peak – doubly so if the original temperature spike was due to only orbital tilt as RealClimate asserts.
Admittedly I am not a climate scientist, but I do think that an orbital tilt change would not reverse so quickly.
c1ue,
You make a great point.
If CO2 was capable of triggering strongly positive feedbacks, the ice core would show it.
Using Trenbeth’s figures:
Annual rainfall (I believe this is from Trenberth’s energy balance
paper) = 1m/year
Latent heat flux = 1000kg/m2*2.26MJ/kg/3600/24/365= 71.6 W/m2
The forcing for water vapor is supposed to be about 15 watts for a
doubling.
The increase in temperature from from a doubling of CO2, without
feedback, is acknowledged by everyone to be about 3.8 watts/m^2, which
would result in an increase of around 1C. I’ve seen actual estimates
ranging from 0.7 C to 1.2 C. With a 1C increase, the saturation level
of water vapor would increase 8%. That 8% increase implies a
[(ln 1.08)/(ln 2)] * 15 watts = 0.0770/0.6931 = 1.67 watts/m^2.
If there was NO increase in precipitation, NO change in convection, No
change in clouds, this would result in a temperature of about [(3.8 +
1.67)/(3.8)]* 1C
= 1.44 C. Right away we see that the “feedback” factors giving a 3 to 6 C increase are crap.
Trenbeth’s figures give about 390 watts in heating the surface
directly, 22 watts convection, and 78 watts in latent heat, somewhat
higher than my computed estimate of 71.6 watts/m^2. I suppose average rainfall is about 78/71.6 = 1.09 meters. Climate models
predict an increase in precipitation less than the increase in
humidity, around 3% rather than the full 8%.
Multiplying my 71.6 watts by that 1.03 increse in precipitation gives
73.75, for an increase in watts of 2.1 in latent heat of
vaporization. The net increase in SURFACE flux with a doubling of CO2
and water vapor feedback would be
390 + 1.67 -2.1, or a DECREASE of 0.43 watts! Note that there would be
more heat in the lower atmosphere, an extra 3.8 + 1.67 watts, but much
of it would be eaten up in LATENT heat- radiated higher in the atmosphere, with actual surface
temperature decreases .
Probably the increase in precipitation cannot be 3%, but
intuitively there would be SOME increase in precipitation, and in
conduction from the surface, eating up part of that 1.67 extra watt
feedback from water vapor.
Note that John Christy reported on an acutal experiment in increasing water vapor, due to
irrigation of the San Joaquin Valley.
http://ams.confex.com/ams/pdfpapers/68739.pdf
Daytime temperatures dropped slightly during the summer, nighttime temperatures increasedsignificantly due to vapor condensation at night, preventing large drops in nighttime temepratures- agreeing with my off the cuff computation of a negative daytime temperature effect due to water vapor- A. McIntire
You use the arguement that increasing temperature at the surface has to cause increasing outgoing radiation or there would be runaway heating. This is looking at the wrong end of the problem. For the moment ignore clouds and separate feedback (for a simplified discussion) and just look at a case where a greenhouse gas level is increasing and thus raising ground temperature. The Solar input is not changing in that simplified case, and radioactive (ground heat) is also the same. Thus the energy flux in is constant. If the temperature is increasing on the ground, the outgoing energy flux has to be decreasing to allow extra energy to be accumulating at the ground level. However, this is a transient state. If the increasing greenhouse gas then leveled off, the outgoing energy would eventually catch up with the incoming, and the temperature would stabelize at a higher level. The unbalance only occurs when the level is changing (as CO2 presently is).
This demonstrates, using GISS data, that the net feedback operating on the system is negative. It also shows a whole lot more and I believe it presents incontrovertible evidence that AGW can’t be a problem.
http://www.palisad.com/co2/eb/eb.html
Regards,
George
Leonard Weinstein,
It is PHYSICS like the IPCC people like to say. As anything gets warmer its radiation increases.
The idea that GG’s delays radiation enough to actually cause a noteable effect is something you will eventually get over.
Perhaps someone could explain to me why the temperature doesn’t run away without even without CO2. If temperature goes up by a small amount, water vapor pressure goes up correspondingly, thus increasing greenhouse gas. This raises temerature even more, continuing the cycle. Thus temperature increase becomes autocatalytic. Since this does not happen, there must be some mechanism that counteracts this effect which we do not understand.
Since water vapor alone can do the deed, CO2 is really not required to have runaway temperature increase, if greenhouse gas is the culprit. Something is really wrong with our thinking here.
Ted Rado,
Exactly. The AGW promoters have turned CO2 into a magic potion.
Fact number one: most of the absorption and re-emission of CO2 happens in the first 20 ppm. That signal is primarily the contribution of the planet. Approx 95 %. Any further contribution hads just about nothing to the process. And this process is only happening mainly at 2.5 microns and 15.7 microns. And CO2 cannot direct its re-emission only toward the earth. Like any radiative product, it goes in all directions. That is why the Earth is still radiating as it as always been, per Lindzen’s study.
Secondly, convection (Ya’ll remember thermodynamics?) No object is holding in heat. Heat always moves from hot to cold, high energy to low energy. All an object can do is change the rate of heat exchange. It’s why your air conditioner works.
Short answer: CO2 is not warming the planet and the atmosphere, in general, acts somewhat like an heat exchanger.
CO2 does act like a heat exchanger in that it absorbs radiation very readily (esp at the lambdas you mentioned). So does water. So do all the other greenhouse gasses. But this isn’t the problem, its the re-radiation from these bodies that is the true problem. Of course the CO2 doesn’t “choose” to direct its heat re-radiation anywhere, however a solid body will absorb comparatively more radiation than surrounding distant molecules in the atmosphere. So the terrestrial earth should then show signs of heating as it is a better absorber of these longer wavelengths than the atmosphere. Oh, and it does. Vostok, ocean coring, tree rings, and many many other proxes agree to a staggering effect. Perhaps all the CO2 we blow into the atmosphere is not the cause of the record concentrations seen today, but I think you’ll have a hard time finding this unknown source of CO2… Wouldn’t it be pretty obvious?
“specifically, I didn’t understand how an increase in temperature could result in a decrease in outgoing radiation, as Lindzen says is assumed in all the models.”
re-read it Lindzen & Choi assurt that as surface temps increase radiation to space also increases, where as the IPCC models hold the opposite to be true. (IE green house effect, due to Co2 holding /stopping/ reflecting the heat back into the earths atmosphere). In other words, in “all the models” it is assumed is that the increase of Co2 in-turn increases the temperature, and the increase of temperature in-turn further increases the temperature because less can radiate out of the atmosphere due to the Co2. So their study was on the effects of temperature and radiation, which found that increases in temperature are marked by strong increases in radiation. In the entire scheme of things, the likely result is that the increase of temperature is not due to increased rates of Co2. Its case and point.
I do not read in Lindzen & Choi that increasing temperature results in decreasing outgoing radiation as you infer… it is rather that each increment of observed temperature contributes to much higher proportion of outgoing radiation flux than is assumed in all the models.
The climate hypothesis has now become a flexible bucket. Throw any empirical data into it, and it just expands.
That is:
I claim that the moon is fully cheese.
You go to the moon. Come back with gravel.
I claim that the moon is almost fully cheese, but gravel in some places.
You go back to the moon. Come back with even more gravel and a few largers stones.
I claim that the moon is fully cheese, exept for a few places, where there is gravel and a few large stones.
You go back to the moon, etc,etc…
We now have a hypothesis that can not be disproved. It only expands to encompass any criticism.
It is irrefutable.
Lindzen&Choi proves only one thing: but most important:
No negative atmospheric feedback.
Ergo: for each doubeling of CO2, the resulting warming diminishes.
A strike to the very heart of the climate hypothesis.
I don’t understand the objections to Dr. Lindzen’s paper; the objections seem to be impossible on their surface.
If you draw a boundary between the outer atmosphere and space and treat the planet (with atmosphere) as a closed system, at equilibrium the amount of energy released through the boundary must be equal to the amount of energy passing into the boundary from the sun. As a baseline, everyone assumes that the amount of energy passing into the system from the sun remains constant. If the temperature of the system inside the boundary is to increase, it is absolutely necessary that the total energy passing through the boundary must go down, at least temporarily, permanently trapping the energy in the system and raising the system temperature.
Dr. Lindzen’s paper shows that once a temperature increase occurs — regardless of the reason — the system responds by moving out of equilibrium and releasing more energy into space than is provided by the sun. Thus, the temperate falls from the new (perturbed) temperature to a level between the initial equilibrium and the post-perturbation temperatures, until the equilibrium is reestablished.
Any model that results in a system temperature above the initial perturbation (above roughly 1C for doubling of CO2) MUST, mathematically, do so by reducing net radiation released into space below the equilibrium point so that the additional energy can accumulate and the temperature can rise. Only by reducing net energy released into space can the system heat itself. All other forms of heating must, by definition, simply move energy within the closed system resulting in redistribution of energy but no net heating.
The author of the note above notes “Models that assumed otherwise [from increased radiation resulting from increased temperature] would have near infinite temepratures.” Dr. Lindzen addresses this explicitly in his paper. “Indeed, Figure 3c suggests that models should have a range of sensitivities extending from about 1.5C to infinite sensitivity (rather than 5C 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.”
I often find that scientists over-complicate matters. If you treat climate change as a simple energy balance equation around the Earth’s atmosphere, Dr. Lindzen’s findings make perfect sense.