Guest article by Andrew Dessler
I have a paper in this week’s issue of Science on the cloud feedback that may be of interest to realclimate readers. As you may know, clouds are important regulators of the amount of energy in and out of the climate system. Clouds both reflect sunlight back to space and trap infrared radiation and keep it from escaping to space. Changes in clouds can therefore have profound impacts on our climate.
A positive cloud feedback loop posits a scenario whereby an initial warming of the planet, caused, for example, by increases in greenhouse gases, causes clouds to trap more energy and lead to further warming. Such a process amplifies the direct heating by greenhouse gases. Models have been long predicted this, but testing the models has proved difficult.
Making the issue even more contentious, some of the more credible skeptics out there (e.g., Lindzen, Spencer) have been arguing that clouds behave quite differently from that predicted by models. In fact, they argue, clouds will stabilize the climate and prevent climate change from occurring (i.e., clouds will provide a negative feedback).
In my new paper, I calculate the energy trapped by clouds and observe how it varies as the climate warms and cools during El Nino-Southern Oscillation (ENSO) cycles. I find that, as the climate warms, clouds trap an additional 0.54±0.74W/m2 for every degree of warming. Thus, the cloud feedback is likely positive, but I cannot rule out a slight negative feedback.
It is important to note that while a slight negative feedback cannot be ruled out, the data do not support a negative feedback large enough to substantially cancel the well-established positive feedbacks, such as water vapor, as Lindzen and Spencer would argue.
I have also compared the results to climate models. Taken as a group, the models substantially reproduce the observations. This increases my confidence that the models are accurately simulating the variations of clouds with climate change.
Obviously, climate skeptics are quite upset with my results. Dr. Roy Spencer, for example, has been criticizing my paper on his blog. Dr. Spencer’s argument is, as he wrote in an e-mail to Dr. Richard Kerr of Science:
Andy’s study assumes that all co-variations between clouds and temperature are due to feedback, when in fact they are a mixture of feedback and “internal forcing” (natural cloud fluctuation causing temperature changes).
Now, Andy DOES at least raise this as a possibility, referencing our (Spencer & Braswell) 2010 JGR paper on the subject (his ref. #26). But he then claims that since (1) ENSO is the main source of climate variability during 2000-2010, and since (2) no one has demonstrated that ENSO is in any way caused by cloud changes, that our cause-versus-effect claim does not apply to the 2000-2010 time period.
His second claim is incorrect.
As Fig. 4a in our paper (http://www.drroyspencer.com/wp-content/uploads/Spencer-Braswell-JGR-2010.pdf ) shows, the major 2007-08 La Nina event shows the characteristic looping pattern in temperature-versus-radiative flux data that results from clouds causing temperature changes
In other words, Dr. Spencer is arguing that clouds are causing ENSO cycles, so the direction of causality in my analysis is incorrect and my conclusions are in error.
After reading this, I initiated a cordial and useful exchange of e-mails with Dr. Spencer (you can read the full e-mail exchange here). We ultimately agreed that the fundamental disagreement between us is over what causes ENSO. Short paraphrase:
Spencer: ENSO is caused by clouds. You cannot infer the response of clouds to surface temperature in such a situation.
Dessler: ENSO is not caused by clouds, but is driven by internal dynamics of the ocean-atmosphere system. Clouds may amplify the warming, and that’s the cloud feedback I’m trying to measure.
My position is the mainstream one, backed up by decades of research. This mainstream theory is quite successful at simulating almost all of the aspects of ENSO.
Dr. Spencer, on the other hand, is as far out of the mainstream when it comes to ENSO as he is when it comes to climate change. He is advancing here a completely new and untested theory of ENSO — based on just one figure in one of his papers (and, as I told him in one of our e-mails, there are other interpretations of those data that do not agree with his interpretation).
Thus, the burden of proof is Dr. Spencer to show that his theory of causality during ENSO is correct. He is, at present, far from meeting that burden. And until Dr. Spencer satisfies this burden, I don’t think anyone can take his criticisms seriously.
It’s also worth noting that the picture I’m painting of our disagreement (and backed up by the e-mail exchange linked above) is quite different from the picture provided by Dr. Spencer on his blog. His blog is full of conspiracies and purposeful suppression of the truth. In particular, he accuses me of ignoring his work. But as you can see, I have not ignored it — I have dismissed it because I think it has no merit. That’s quite different.
I would also like to respond to his accusation that the timing of the paper is somehow connected to the IPCC’s meeting in Cancun. I can assure everyone that no one pressured me in any aspect of the publication of this paper. As Dr. Spencer knows well, authors have no control over when a paper ultimately gets published.
And as far as my interest in influencing the policy debate goes, I’ll just say that I’m in College Station this week, while Dr. Spencer is in Cancun. In fact, Dr. Spencer had a press conference in Cancun — about my paper. I didn’t have a press conference about my paper. Draw your own conclusion.
I hope that this post has explained my work and cleared up exactly what my disagreement with Dr. Spencer is. If interested readers do some basic research on the causes of ENSO, I’m confident they will agree with me that my interpretation of the data is sound.
Update: For those of you who enjoyed reading the e-mails referenced above on cloud feedback, Andy Dessler is continuing to post the e-mails from ongoing correspondence.
It takes time to reach equilibrium because of the heat capacity of the oceans.
Well, the heat capacity in general; it happens the oceans dominate the effective heat capacity of the climate system (it takes a very very long time for heating signals to penetrate through the crust, etc.)
RW @ 138: The 3K number estimates the *equilibrium* temperature rise (excepting some slow feedbacks like ice-sheet melting) for a CO2 doubling. But earth probably takes 25-50 years to reach 60% of equilibrium temperature [1], and probably centuries to reach 100%, due to ocean heat storage. Thus, the yearly eccentricity-based forcing does not produce anything like the full equilibrium increment of warming or cooling that its peak value would suggest.
[1] Hansen et al 2005, http://meteora.ucsd.edu/cap/pdffiles/Hansen-04-29-05.pdf .
Sorry this question is late. Dr. Dessler (or someone else who knows the answer) it appears from the discussion above that it doesn’t matter whether clouds cause ENSO or whether ENSO causes clouds, but rather what is the radiative change to changes in clouds no matter what the causes of the cloud changes are. The MERRA assimilation is described here http://gmao.gsfc.nasa.gov/pubs/docs/Rienecker369.pdf which essentially integrates satellite radiance measurements into an AGCM. It describes the radiative equations based on, among other factors, clouds, along with convective equations and specific cloud process equations.
It seems to me that the scatterplot in your figure 2A depends on the assumptions implicit in those equations along specific parameters (my link page 19) that are determined by fitting the model radiation to the satellite-measured radiation. There are conceivably a range of solutions with such a large number of variables including potential local minimums. While a solution adds credence to the model in general, how do we know that the modeled clouds behave similarly to clouds in the real world with respect to feedback to warming? Is there are other way to measure cloud feedback than such a model?
re:140 Pakistan flooding and Russian heat
Well, I would say those are examples of paying the piper, but I thought the European heatwave of 5-6 years ago was one, as well. Until there’s something more cinematic (literally) I don’t think we’ll get the public’s attention.
It’s interesting about Pakistan, though. It should have served as an enormous bellwether since a flood that displaced 20,000,000 people and covered 1/5th of a country is huge. But Pakistan is a dangerous Muslim place, and the media in this country definitely downplayed the scope of their tragedy. Whether because of the whole Muslim aspect or because of the flood’s relation to AGW, I don’t know. Both, I suspect.
re: 143
At this stage of the game, I don’t think there are a lot of people weighing the arguments between science and the deniers. I think on the whole people “disbelieve” AGW simply because they don’t want to assume the burdens that mitigation will demand. Why, yes, I’ve become pretty misanthropic in my old age. Why do you ask?
Are you able to say what drives the ocean-atomsphere system?
“…is it correct to say that any of these cloud feedback and/or forcing scenarios do not change the basic CO2 forcing formula?” Rod B — 12 December 2010 @ 2:38 PM
IMHO, no. One thing that I haven’t seen discussed is that cloud scattering of IR photons makes the effective path length longer; and increases the greenhouse effect at a given GHG concentration.
see -
Joint Statistics of Photon Path length and Cloud Optical Depth, Q.-L. Min and L. C. Harrison
“A mean pressure- and temperature-weighted photon pathlength in the atmosphere can be inferred from moderate resolution measurements in the O2 A-band.”
“Two different population branches are apparent in the scattergram of the pathlength versus cloud optical depth; we attribute these to 1) single layer cases exhibiting small variations of pathlength enhancement over large optical depth ranges; and 2) multiple layer cases with large variances of enhanced photon pathlengths.”
“The top panel in Figure 4 shows the time series of mean photon pathlength and cloud optical depth on a day where the pathlength shows much greater variance. Note that this variance is large even for the optical depth > 50 measurements, that occur only after 18:00 Universal Time Coordinates (UTC), where by eye the two seem strongly correlated at the scale of the top panel. Our attribution of the atmospheric state is not certain; we believe this case has a thin and varying upper layer cloud over low stratus. The large pathlength variations then occur due to multiple transits between the layers in cloud-free air that does not contribute to the cloud optical depth.”
The incremental path length differences caused by cloud scattering, inferred from the changes in O2 alpha band absorption, and shown in their figure 4, varied from ~ 10% to 250% longer. IR emissions from the ground at wavelengths which CO2 absorb would likewise experience a longer effective path length to the TOA and larger absorption.
Measuring and modeling this is complicated by such things as nonlinear scattering effects by cloud particles sizes near the CO2 absorption wavelengths, the relative distribution of cloud particle density versus atmospheric pressure, and the vertical profile of cloud density.
Terry (144) – “the authors also found that lack of cloud cover caused a positive SST anomaly ie a -ve feedback”
A lack of cloud cover would be a warming influence. Added to El Nino warming, it would constitute a positive feedback. I do agree that their model involves a series of changing phenomena, but I didn’t see any clear negative feedbacks among them.
BD 153,
There is almost no scattering at infrared wavelengths. The only situation where I can remember it being a major factor is on Venus.
I’m just wondering about Venus. Didn’t it have oceans, and didn’t they vaporize away, and in the process, didn’t the water vapor (some in form of clouds) contribute to the increasing warming? Or does this not relate at all to the discussion here.
Brian Dodge (153), very interesting. It’s hard to see a big effect given the propensity of IR absorption by CO2 rather low in the atmosphere. But it does give food for thought, and, technically at least, forcing (alone) does seem to be affected directly by clouds. Thanks.
Gavin:
[Response: No idea what you are referring to. A global annual mean radiative forcing from the sun (= delta(TSI)/4*0.7 ) has almost exactly the same effect as the same amount of CO2 related forcing.]
Apparently not. If that were true, then the total warming expected from a doubling of CO2 would only be about 0.6 C and not the 3 degrees C predicted. The average amount of positive feedback for each 1 W/m^2 power from the Sun is only about 60% – meaning each 1 W/m^2 of albedo adjusted power coming in from the sun is amplified to about 1.6 W/m^2 at the surface due to the presence of greenhouse gases and/or clouds in the atmosphere. If an additional 2 W/m^2 of power from a doubling of CO2 is treated the same as 2 W/m^2 of additional power from the Sun, the temperature increase would only be about 0.6 C (2 W/m^2 x 1.6 = 3.2 W/m^2 – at 288K a 3.2 W/m^ increase from 390 W/m^2 to 393.2 W/m^2 equals a 0.6 C rise via Stefan-Boltzman).
[Changes related to the orbit which impacts seasonal insolation are a whole other kettle of fish (cf. the ice ages), but don't really fall into a neat radiative forcing argument. - gavin]
Why? Are you saying the perihelion-aphelion insolation changes are not “forcing” the climate?
Patrick:
[If you held Earth at perihelion distance for several decades (or shrunk the semimajor axis to equal the present perihelion distance), you would get that warming (assuming your math is correct; actually for the same forcing efficacy, the warming in deg C or K would be a somewhat smaller than the value of forcing in W/m2; anyway, I’m not sure if I’m remembering the Earth’s orbit’s eccentricity correctly). It takes time to reach equilibrium because of the heat capacity of the oceans.]
Then how do you explain the relatively large and fast seasonal temperature changes that occur in each hemisphere every year? The seasonal hemispheric fluctuations in radiative forcing that occur are astronomically greater than the measly 1.85 W/m^2 that will come from a doubling of CO2. If what you’re saying is true – that the heat capacity of the oceans take decades to reach equilibrium, we wouldn’t see anywhere near the seasonal variability that occurs each year.
[The forcing of a doubling of CO2 is ~ 3.7 W/m2; the 1.85 W/m2 net forcing you refer to would be the remaining disequilibrium after the climate warms approx. halfway to new equilibrium.]
No, the 1.85 W/m^2 is the amount of absorbed power that is radiated downward toward the surface, the other half is radiated upward out to space in the same general direction it was already headed.
Fred #154
Yes you are quite right, and I mis-read the section on heat fluxes w.r.t. different cloud ages. On reflection it is no surprise that the model shows this, as it uses the same cloud feedback regime as most of them. What is interesting tho is that the ENSO events can be simulated purely on an atmospheric basis, which must significantly alter the contribution that atmospherics have in the GCMS.
RW,
What you really need is Tamino’s post, entitled “Not Computer Models,” where he describes a 2-box model, with one box, representing the atmosphere and reacting on a timescale of about a year, and a second box interacting with the first with a timescale of about 30 years. Seasonal changes affect primarily the smaller box (the atmosphere). It ain’t that tough.
BPL (155), so while Brian Dodge’s reference (153) might be correct in that scattering of IR increases the path length and hence affects the forcing, you’re saying that very little (nearly none) IR is subject to scattering by atmospheric molecules and therefore the point of the assertion is moot — correct?
I think I’m missing something pretty basic to the discussion. Maybe someone could help me out? Sometimes, it sounds like the claim at stake is whether increases in temperature are associated with increases (or decreases) in cloud cover — that’s the way Spencer puts it on his blog. (I use “associated with” here so as not to beg the causal question.) On this reading, the effect of a unit of cloud cover is constant (more or less), and the question is just whether warming positively or negatively causes cloud cover, right?
Other times, it sounds like the claim at stake is whether increases in temperature are associated with increases (or decreases) in the influence of cloud cover on temperature — that’s the way I read Dessler. On this reading, the issue isn’t about cloud *cover* at all but about how clouds trap or reflect energy at different temperatures.
Which claim is at stake or is it a hybrid of the two or something else entirely?
RW 161: Why? Are you saying the perihelion-aphelion insolation changes are not “forcing” the climate?
BPL: Those forcings balance every year, and the climate has a thermal equilibrium measured in months, so in the long run, their forcing is irrelevant. Radiative forcing for changing the climate requires a secular trend, and giving it long enough to have a significant effect.
162 (RW),
Seasonal changes are far more a result of the change in angle of incidence and duration of insolation (winter = fewer hours, summer = more hours) which result from the earth’s axial tilt. The total insolation received by a hemisphere can therefore vary greatly (far in excess of the aphelion/perihelion difference), causing great temperature swings with the seasons, but the total insolation of the planet as a whole remains constant (with the exception of the 14 W/m^2 to which you refer).
The main points are that:
1) The dramatic seasonal warming that you see is a result of axial tilt, not distance from the sun.
2) The warming you see in one hemisphere is countered by cooling in the other; it’s not exactly proportional, because of the differences in land masses and resulting snow/ice cover in the two hemispheres, but it’s close enough. You’re not talking about global warming or cooling (much), but rather hemispheric warming/cooling, which is a quite different animal.
3) The 14W/m^2 that you are talking about is relatively short lived (3 months, and most of that at less than 14W/m^2?), so while the hemispheres may warm/cool dramatically as a result of huge changes in insolation due to axial tilt (24 hours of daylight at one pole versus 0 hours of daylight at the other, in the extreme case), the planet as a whole does not have time to react to the change.
BPL “There is almost no scattering at infrared wavelengths. ”
There are lotsa cloud particles in the 10-30 micron size[1], which I would expect to scatter infrared in the important wavelengths strongly[2] – Mie scattering, resonance effects, and the high dielectric constant of water. The IR absorption and thermal emission of water and ice will overlap some of the CO2 lines, further complicating analysis.
Unfortunately http://isccp.giss.nasa.gov/climanal9.html “Effects of Clouds on Longwave Fluxes” “…is currently under construction.”
[1] http://isccp.giss.nasa.gov/cloudtypes.html
“The standard ISCCP products assume that clouds warmer than 260 K are liquid clouds composed of spherical droplets with an effective radius of 10 microns and that colder clouds are ice clouds composed of crystals with a fractal shape (aspect ratio unity) that have an effective radius of 30 microns. ”
[2] http://lasp.colorado.edu/~bagenal/1010/graphics/earth_ir_emission.gif
Barten:
RE: [BPL: Those forcings balance every year, and the climate has a thermal equilibrium measured in months, so in the long run, their forcing is irrelevant. Radiative forcing for changing the climate requires a secular trend, and giving it long enough to have a significant effect.]
I thought the climate has a thermal equilibrium that takes decades, not months? That’s what was claimed a few posts back by Patrick (and a think a few others). So which is it – months or decades?
If the “significant effects” of changes in radiative forcing take so long (i.e. months or decades), then why do we see such wide temperature swings from day to night, for example?
Bob,
RE:[Seasonal changes are far more a result of the change in angle of incidence and duration of insolation (winter = fewer hours, summer = more hours) which result from the earth’s axial tilt. The total insolation received by a hemisphere can therefore vary greatly (far in excess of the aphelion/perihelion difference), causing great temperature swings with the seasons, but the total insolation of the planet as a whole remains constant (with the exception of the 14 W/m^2 to which you refer).]
I never claimed or implied otherwise.
RE:[The main points are that:
1) The dramatic seasonal warming that you see is a result of axial tilt, not distance from the sun.
2) The warming you see in one hemisphere is countered by cooling in the other; it’s not exactly proportional, because of the differences in land masses and resulting snow/ice cover in the two hemispheres, but it’s close enough. You’re not talking about global warming or cooling (much), but rather hemispheric warming/cooling, which is a quite different animal.]
Why a different animal, fundamentally? The seasonal changes are a response to changes in radiative forcing – are they not? In fact, they are a response to a far, far larger change in radiative forcing than what would come from a doubling of CO2, yet the response is very quick – certainly not multiple months, otherwise the coldest or warmest temperatures wouldn’t occur until several months after the maximum angle of the tilt. There is a delay, but it’s only about one month.
RE: 3) The 14W/m^2 that you are talking about is relatively short lived (3 months, and most of that at less than 14W/m^2?), so while the hemispheres may warm/cool dramatically as a result of huge changes in insolation due to axial tilt (24 hours of daylight at one pole versus 0 hours of daylight at the other, in the extreme case), the planet as a whole does not have time to react to the change.]
Again, why not? Are you saying the +14 W/m^2 are not “forcing” the whole planet? I understand it would be proportionally less during the northern hemisphere winter than the southern hemisphere summer, but how is that relevant to the planet as whole?
http://journals.ametsoc.org/doi/abs/10.1175/1520-0442%281999%29012%3C0159%3APFCLSF%3E2.0.CO%3B2
Chou, Ming-Dah, Kyu-Tae Lee, Si-Chee Tsay, Qiang Fu, 1999: Parameterization for Cloud Longwave Scattering for Use in Atmospheric Models. J. Climate, 12, 159–169.
“With the scaling approximation, radiative transfer equations for a cloudy atmosphere are identical with those for a clear atmosphere, and the difficulties in applying a multiple-scattering algorithm to a partly cloudy atmosphere (assuming homogeneous clouds) are avoided. The computational efficiency is practically the same as that for a clear atmosphere. The parameterization represents a significant reduction in one source of the errors involved in the calculation of longwave cooling in cloudy atmospheres.”
(Cited By many; see that list for mention of GISS Model E)
Re 162 RW Then how do you explain the relatively large and fast seasonal temperature changes that occur in each hemisphere every year? The seasonal hemispheric fluctuations in radiative forcing that occur are astronomically greater than the measly 1.85 W/m^2 that will come from a doubling of CO2. If what you’re saying is true – that the heat capacity of the oceans take decades to reach equilibrium, we wouldn’t see anywhere near the seasonal variability that occurs each year.
You answered part of your own question: the seasonal forcing is much larger. (And actually, global circulation would tend to reduce the seasonal cycle (heat flux from summer to winter) whereas perihelion-aphelion differences have a global effect.) Also, compare seasonal variations over land to over the ocean. Also, when ice forms over the ocean it allows the air above to cool without as much heat flux from the water. Also, feedbacks won’t be the same everywhere.
the 1.85 W/m^2 is the amount of absorbed power that is radiated downward toward the surface, the other half is radiated upward out to space in the same general direction it was already headed.
No, radiative forcing is defined as a change in a flux (per unit area) – in this context, defined as the change in net downward flux (per unit area) (change in net downward = change in downward minus change in upward) (in this case, at the tropopause level after stratospheric adjustment). It is not the total increase in emission from the atmosphere (which is not in general evenly divided between upward and downward fluxes – the atmosphere is not isothermal and for that matter, water vapor and clouds are not evenly distributed over the mass of the atmosphere, or even just the troposphere).
“Then how do you explain the relatively large and fast seasonal temperature changes that occur in each hemisphere every year? ”
Because of the tilt of the earth, the amount of sunlight energy hitting my yard at noon varies by a factor of ~2 between summertime when the sun is ~12.5 degrees from directly overhead, and wintertime, when it only gets to about 30.5 degrees above the horizon.The January – July temperature difference is about 40 deg F. Dallas has a 1.9 summer-winter ratio, and a 41 degree temp range. Miami has a 1.5 ratio, and a 20 degree temperature difference; Fairbanks has an insolation ratio of 7.1, and a 73 degree Jan-July temperature difference. Quito ecuador, near the equator, has an average monthly temperature of 20-21 degrees centigrade year round, There’s a definite trend here, but altitude, proximity to large bodies of water, being windward or leeward of mountain ranges all have additional effects.
Re RW – large diurnal (day-night) temperature swings – you don’t see that over the ocean, it’s a land thing (and reduced at lower elevations, greater humidity or cloud cover, and affected by surface characteristics). And it’s from a huge forcing (hundreds of W/m2).
(PS I think it should be easier to get larger temperature swings relative to forcing for localized areas over shorter time periods, when the atmospheric circulation hasn’t had time to redistribute the effect. Over time, oceanic heat capacity acts on temperature over land.)
RW 170,
For seasons it’s months. For daily local temperatures it’s hours. For climate it’s years. Different processes on different time scales.
171 (RW),
Are you asking a legitimate question, because you are confused and are trying to puzzle out the flaw in your own logic, or are you trying to “put another nail in the coffin of AGW belief” with your own dramatically novel insight?
If it’s the latter, you should consider that no one on the planet has ever tried your argument (that I know of), including real “skeptic” scientists like Lindzen and Spencer. No one has any issue with the forcing difference between aphelion and perihelion or the seasons versus CO2, so if you think you’ve hit on something dramatically insightful, you should extend yourself pretty far (with a truly skeptical point of view) in trying to figure out where maybe you have misunderstood things that the rest of the world has gotten right, rather than the dramatically Galilean opposite (i.e. you’re right, and the whole civilized world is wrong).
[And mind you, even Galileo was not alone. He was in fact preceded by Copernicus in his beliefs, and shared them with a fair number of educated contemporaries. His distinction was in having the courage to openly, publicly push it. But it was primarily the theologists and philosophers who where offended and threatened by his position (the equivalent of today's economic reactionaries and fossil fuel interests), and not the people who were more learned in mathematics. As a note, "scientists" did not exist at the time, so "philosophers" were the scientists, or rather, there was no clear distinction between the two, except, perhaps, in each individual's true nature.]
If you honestly want to know where your logic is flawed, kindly do some research, think things through further, and when you think you’ve gone as far as you can alone, ask again about any particulars and you will get help here.
If you think you’ve somehow found a salient point that no one can possibly refute, kindly do some serious research, seriously think things through, but don’t expect any responses here much beyond frustration and slowly building annoyance. It’s a non-starter.
Possibly the least OT for any current thread–I’ve got a new article up today touching upon some of the basic science we’re discussing here, and would appreciate corrections/criticisms/suggestions from any kind (and astute!) souls willing to take a look:
http://hubpages.com/hub/Water-Is-A-Dancer
(Cross-posted at “Open Mind.”)
Regarding Comment 106 by William “Although there was a correlation between GCRs and low-level cloud cover until about 1991, after that point the correlation broke down (Laut 2003) and cloud cover began to lag GCR trends by over 6 months, while cloud formation should occur within several days (Yu 2000).”
FYI, following study suggests a small but “statistically robust relationship” between short-term GCR flux changes and rapid mid-latitude cloud decreases over the past 20 years. Correlation persists.
Cosmic rays linked to rapid mid-latitude cloud changes – Laken, Kniveton, Frogley (2010)
http://www.atmos-chem-phys.net/10/10941/2010/acp-10-10941-2010.pdf
re clouds etc., Tenney Naumer sent me this and I’ve been feasting on it (visually) from time to time.
For a relative layperson, the demonstration of the obvious: that light and dark is a sine wave, is striking here as well.
Seems to Eli that a lot of the problem here (and with RS) is limiting El Nino to being a purely temperature effect. There are major changes in wind and sea currents.
To add to the various replies to RW, you can quantify the seasonal forcing due to the change in sun angle at a typical location as 200 W/m2 in the daytime, or 70 W/m2 diurnally averaged.. This is much bigger than the elliptical orbit effect of 14 W/m2.
Re my 175 (re RW)
(PS I think it should be easier to get larger temperature swings relative to forcing for localized areas over shorter time periods, when the atmospheric circulation hasn’t had time to redistribute the effect. Over time, oceanic heat capacity acts on temperature over land.)
I could have explained this better:
If you have some heat capacity C and apply a change in forcing RF, equilibrium temperature changes sharply, but the actual temperature must change gradually, decaying exponentially on a time scale proportional to C (for climate change, the time scale is proportional to C * climate sensitivity – because climate sensitivity is higher when a given temperature change causes a smaller reduction in the imbalance in the heat fluxes).
If you only apply a forcing to some small heat capacity, then it may at first decay toward the new equilibrium at a fast rate; however, if heating or cooling changes can spread out from this heat capacity to other heat capacity (atmospheric and oceanic circulation), then as the time progresses to a scale where this spreading is significant, the decay toward the new equilibrium slows, and actually the temperature will not reach a local equilibrium because a larger system is responding to the localized forcing.
Farther to mine and other’s points – the diurnal and seasonal forcings are quite large; the responses are large. If you (RW) were trying to construct an argument based on the idea that these responses are large because they are near equilibrium, you’d be wrong. Consider that the polar winter night, or any night time, the local equilibrium temperature would hover just above absolute zero (that’s -273.15 deg C). It never gets anywhere near this cold, even in Antarctica. Yes, in part because of atmospheric and oceanic circulation (Antarctica, being an snow/ice surface, I would guess might get quite a bit closer to absolute zero in the absence of heat fluxes from lower latitudes, but I’m not sure just how close – you’d need to take the thermal conductivity and heat capacity of the surface material into account) – so this observation doesn’t entirely suffice to illustrate the effect of heat capacity alone (although it would be hard for circulations to transport heat if the material had no heat capacity – the air reaching Antarctica in winter would be much colder if it reached such a locally-determined equilibrium; the heat capacity reduces the amount of cooling that can occur during the time it takes for circulation to transport material) – but it does illustrate that you’re (RW) observations do not suffice to make a case for small climate sensitivity – or larger climate sensitivity (after all, you suggested the lack of response to perihelion would suggest low climate sensitivity (it would if heat capacity were much smaller), and then argued that heat capacity must be small because of the large responses to diurnal and seasonal forcings (which would suggest large climate sensitivity if the forcings were smaller or the heat capacity acting on those scales were larger).
@ Kevin McKinney — 16 December 2010 @ 12:40 PM
“…, when “normal” rain containing natural carbonic acid falls upon silicon-containing sedimentary rocks…”
The important processes for geological sequestration are more complex. The important source rocks are volcanic/igneous, and the important components are the various complex silicates contained therein.
Basalt/Gabbro – pyroxene, plagioclase feldspar, amphibole, and olivine
-http://en.wikipedia.org/wiki/Pyroxene
-http://en.wikipedia.org/wiki/Feldspar
-http://en.wikipedia.org/wiki/Amphibole
Andesite/Diorite – feldspar, biotite, hornblende, pyroxene
-http://en.wikipedia.org/wiki/Hornblende
-http://en.wikipedia.org/wiki/Mica
Dacite/Granodiorite – plagioclase feldspar with biotite(mica), hornblende, pyroxene, and quartz
Rhyolite/Granite – quartz, alkali and plagioclase feldspar, biotite and hornblende
Physical weathering breaks up these rocks into fine particles(clays), and concurrent dissolution and chemical weathering allows the replacement of the SiO2 anion with the carbonate anion. The solid metal-(aluminum)-silicates plus CO2 gas are transformed into solid (or dissolved) metal carbonates, and solid (aluminum)-silicates, or silica. – http://en.wikipedia.org/wiki/Kaolinite
The source rocks aren’t very soluble, but the large surface area created by weathering allow the reactions to sequester CO2 on geologic time scales. The most important metal is calcium, but magnesium and iron also play a role. The sodium and potassium compounds largely remain in solution, although natural evaporite deposits of sodium carbonates occur. – http://en.wikipedia.org/wiki/Sodium_carbonate
Well put.
Cranks, of course, never consider this preliminary step before unleashing their brilliant insights on an astonished world. RW’s next effort will no doubt reveal whether he has simply overlooked this elementary precaution, or dismisses it as unnecessary in light of the obvious genius of his ideas.
Dr Dessler,
Thank you for taking the time to explain your results to interested non-scientists.
You write:
quote
But aerosols’ radiative impact is not expected to
correlate with DTs, so the effect of aerosols is to
add uncertainty to the cloud feedback calculation
but should not introduce a bias.
unquote
My particular interest is aerosols and the effects of pollution on their production. I can think of two mechanisms which might alter their numbers during ENSO events. Varying windspeeds will change the number and vigour of breaking waves — by an amount which is presumably quantifiable — and stratification will change phytoplankton populations and hence DMS levels in the ocean/atmosphere boundary layer.
Both mechanisms will be correlated with SST changes to some extent — again by an amount which is presumably quantifiable. My guess is lower windspeeds and/or higher SSTs would lead to fewer aerosols, but I am, of course, open to actual measurements correcting that guess.
Would accounting for these changes influence the conclusions of your paper re a possible bias? Are there any measurements of aerosol changes during ENSO events which could be plugged into your analysis?
TIA.
Julian Flood