A new paper just published in the Journal of Climate finds that global cloudiness has decreased over the past 39 years from between 0.9 to 2.8% by continent as shown in the figure below:
DJF. Continental seasonal anomalies are based on seasonal station anomalies averaged within 10˚ grid
boxes, which are then averaged over the continent weighted by land fraction and box size. Interannual
variation (IAV) is the standard deviation of the time series. Trends are determined using the median of
pairwise slopes method.
The period of the study is from 1971 to 2009. The authors say that:
“Global average trends of cloud cover suggest a small decline in total cloud cover, on the order of 0.4% per decade.”
Taken together, global cloud cover decreased and average of 1.56% over this 39 year period. WUWT readers may recall that Dr. Roy Spencer points out the issue of a slight change in cloud cover in his 2010 book intro of The Great Global Warming Blunder: How Mother Nature Fooled the World’s Top Climate Scientists. He writes:
“The most obvious way for warming to be caused naturally is for small, natural fluctuations in the circulation patterns of the atmosphere and ocean to result in a 1% or 2% decrease in global cloud cover. Clouds are the Earth’s sunshade, and if cloud cover changes for any reason, you have global warming — or global cooling.”
So there you have it, by the work of independent scientists, it is suggested that Dr. Spencer’s hypothesis of just a small change (1-2%) of cloud cover has been observed in their study. This can account for the global warming changes observed. Cloud cover has decreased over the past 39 years globally, and temperatures have risen during that time. This global decrease in cloud cover alone could account for all surface warming observed since the 1970’s. Interestingly, some types of clouds have been on the increase, while others have been on the decrease. Figure 2 shows this:
40˚-80˚N, and 20˚-180˚ E. Anomalies are calculated for individual stations, then averaged within 10˚
equal-area grid boxes, box values are averaged over the entire area, weighted by box size and land
fraction in each box.
Now, a cause needs to be identified as to why some clouds increase and others decrease. One of the obvious ones to examine is Svensmark’s cosmic ray hypothesis, which says that as solar (magnetic) activity decreases, cosmic ray insolation intensity increases, and cloud cover increases due to more cosmic ray seeding. Aerosols and ENSO may also figure greatly in cloud formation changes. It will be a tough puzzle to fully disentangle given that there have been a number of stations lost that record cloud cover type and the move has been towards automated systems (like ASOS) which only record cloud height and not type. The data in this study is mostly from human observers noting cloud type and height for aviation purposes. Perhaps there will be a way to get this information as the number of observers decrease from satellite image processing.
Here’s the paper:
Ryan Eastman and Stephen G. Warren
Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195 Journal of Climate 2012: http://dx.doi.org/10.1175/JCLI-D-12-00280.1
Abstract
An archive of land-based, surface-observed cloud reports has been updated and now spans 39 years from 1971 through 2009. Cloud-type information at weather stations is available in individual reports or in long-term, seasonal, and monthly averages. A shift to a new data source and the automation of cloud reporting in some countries has reduced the number of available stations; however this dataset still represents most of the global land area.
Global average trends of cloud cover suggest a small decline in total cloud cover, on the order of 0.4% per decade. Declining clouds in middle latitudes at high and middle levels appear responsible for this trend. An analysis of zonal cloud cover changes suggests poleward shifts of the jet streams in both hemispheres. The observed displacement agrees with other studies.
Changes seen in cloud types associated with the Indian monsoon are consistent with previous work suggesting that increased pollution (black carbon) may be affecting monsoonal precipitation, causing drought in North India. A similar analysis over northern China does not show an obvious aerosol connection.
Past reports claiming a shift from stratiform to cumuliform cloud types over Russia were apparently partially based on spurious data. When the faulty stations are removed, a tradeoff of stratiform and cumuliform cloud cover is still observed, but muted, over much of northern Eurasia.
====================================
The full paper is available on the author’s website:
http://www.atmos.washington.edu/~rmeast/Full_Text_D1.pdf
Dr. Spencer’s book is available from Amazon:
Philip Bradley says:
August 21, 2012 at 2:06 pm
“More cloud seeding elements result in more and smaller droplets. which cause the clouds to be more persistent.”
Maybe. But then you might have such a density that the drops start to coalesce, with resulting rain, dissipating the cloud cover. Then again, the droplets are ionized, so perhaps they will repel one another, resulting in very diffuse cloudiness, resulting in reduced albedo.
Is this really such as linear relationship as you suggest? Does anyone really know clouds at all?
I’m surprised no one has mentioned Miskolczi. If the water vapor has dropped it is exactly as he has claimed with is constant optical depth. In other words, the overall GHE has been constant and cannot be the cause of any warming.
”
Simple physics teaches us that less cloud is to be expected in a warmer atmosphere.”
No, simple physics does not tell us that there should be less clouds in a warmer world. How on earth do you argue for such an oversimplistic idea and wrong to both?
Crispin in Waterloo says:
August 21, 2012 at 2:36 pm
I see a clear general relationship (correlation) between GCR’s for some years and then there is a total disconnect, a view shared by the authors.
This is the usual fate of spurious correlations. Somebody picks up what look like a good correlation and then later the effect goes away.
If the data is not reliable enough to detect the correlation, then it would be hard to argue persuasively that it is not there.
Even harder to argue that there is an effect.
Would you be so kind as to explain the meaning of the “geomagnetic cutoff rigidity of 2.32 GV” in Kiel v.s. the geomagnetic cutoff rigidity of 9.56 GeV in Beijing?
A charged particle is deflected by a magnetic field. It is harder to deflect a particle with high energy, so lower energy particles are deflected a lot, so much, in fact, that for each place on the Earth the is minimum energy a particle must have in order to reach the surface. That is called the cutoff rigidity. It is largest at low latitudes and dwindles to zero at the poles.
the point is easily made that it was the lower energy and thus most easily deflected GCR’s that were not reaching the Earth before, and now they are. As a result I must judge the paper to be inadequate in terms of falsifying or even significantly denting the Svensmark hypothesis.
There is some confusion here. The Earth’s magnetic field deflects cosmic rays and the solar wind does too, but in different ways. Above, say 20 GeV, there is almost no modulation by the Sun [no deflection], but all of those rays reach the Earth’s surface [also no deflection]. Below 10 GeV there is some modulation by the Sun [i.e. a solar cycle variation of the intensity of the cosmic rays] but most of those rays do not reach low latitudes. So there is a ‘sweet’ spot somewhere between 10 and 20 GeV where there is just enough modulation by the Sun and where just enough rays reach the surface. Svensmark needs to hit that sweet spot [a special pleading] for the effect to work. And herein lies his problem. The Earth’s deflecting ‘power’ depends on its magnetic field [stronger field = more deflection]. In the last several hundred years the Earth’s magnetic field has become weaker, so more cosmic rays reaches the surface which should have cooled the Earth [according to Svensmark] the past few hundred years, yet the Earth has warmed [‘climbed out of the LIA’ people say].
If there is a paper that discloses the energy level of the GCR’s and shows any previous and current correlation, or lack of it, to cloudiness at the predicted altitudes and latitudes, I would be very interested to read it.
The paper I referred you to is a good start.
Pierce and Adams also discusses the energy aspect:
http://www.seas.harvard.edu/climate/eli/Courses/global-change-debates/Sources/03-Cosmic-rays/more/Pierce-Adams-2009-GRL.pdf
In some of the early papers, an energy of 13 GeV was suggested as being causative: http://rivernet.ncsu.edu/courselocker/PaleoClimate/Marsh%20Svensmark%202000%20Cosmic%20Rays%20Clouds%20and%20Climate.pdf
But it is really difficult to pin this down as ir seems to a moving target.
One would think that Svensmark himslef would have written such a definitive paper, but it seems to lacking.
Crispin in Waterloo says:
August 21, 2012 at 2:36 pm
If there is a paper that discloses the energy level of the GCR’s and shows any previous and current correlation, or lack of it, to cloudiness at the predicted altitudes and latitudes, I would be very interested to read it.
The paper I referred you to is a good start.
Pierce and Adams also discusses the energy aspect:
http://www.seas.harvard.edu/climate/eli/Courses/global-change-debates/Sources/03-Cosmic-rays/more/Pierce-Adams-2009-GRL.pdf
In some of the early papers, an energy of 13 GeV was suggested as being causative: http://rivernet.ncsu.edu/courselocker/PaleoClimate/Marsh%20Svensmark%202000%20Cosmic%20Rays%20Clouds%20and%20Climate.pdf
But it is really difficult to pin this down as ir seems to a moving target.
One would think that Svensmark himself would have written such a definitive up-to-date paper, but it seems to lacking. Here he describes the early theory: http://rivernet.ncsu.edu/courselocker/PaleoClimate/Marsh%20Svensmark%202000%20Cosmic%20Rays%20Clouds%20and%20Climate.pdf
docrichard says:
August 21, 2012 at 1:34 pm
““High clouds warm, low clouds cool”.
The only apparent observation is that the air just below cirrus clouds can warm by around 10°C (which sounds like inhibited convection), but I don’t see how -20°C or less up there can make the ground warmer. Are we really to believe that the far larger amounts of cirrus clouds above the tropics are acting as a positive feedback? And again, does an equatorial desert really reach higher midday surface temperatures when cirrus cloud is present?
Our calculated transmission of sunlight through cirrus is much larger than measurements indicate.
Since the transmission is too large, the reflection must be too small. Hence, the cirrus albedo effect is severely underestimated by calculations. Yet these are the type of calculations that are repetitively used in climate prediction models. http://geo.arc.nasa.gov/sge/jskiles/fliers/all_flier_prose/cirrusclimate_kinne/cirrusclimate_kinne.html
Bart says:
August 21, 2012 at 3:19 pm
Is this really such as linear relationship as you suggest? Does anyone really know clouds at all?
I’m agnostic on GCR cloud seeding. I thought the theory elegant, but elegant theories aren’t always right, and as Leif points out, the lack of a consistent correlation is persuasive that GCRs don’t seed clouds.
Perhaps there is some threshold effect at work. As you say, there is a great deal we don’t know about clouds.
The aerosol seeding – cloud persistence relationship is well accepted. And should hold for any seeding agent.
http://iopscience.iop.org/1748-9326/3/2/025002
@docrichard
Breaking it down, there appears to be no trend in cirrus since 1983:
http://isccp.giss.nasa.gov/zD2CLOUDTYPES/B101glbp.anomdevs.jpg
and a decline in cirrostratus from ’83 to ’01 followed by a rise:
http://isccp.giss.nasa.gov/zD2CLOUDTYPES/B106glbp.anomdevs.jpg
Neither of these are following the temp’ changes, unlike low and mid level clouds.
Are we talking about diurnal cloud formation, where the afternoon heat produces cumulonimbus (800-400 mbar), attenuating heat accumulation/transfer from above) during sunny side exposure and attenuating OLR at night?
Opacity is key, both visible, IR, OLR and the surface, between night-side and dayside.
@ur momisugly Leif and Philip B
I appreciate the conversation. I agree that there needs to be more consideration of the precursor conditions. It is spoken of as if there is ‘nothing’ in the air and then a whizz-bang cosmic ray comes along and creates a CCN. The very detailed (agonisingly detailed) explanation of the process I read (not Svensmark) covering every aspect of CCN formation in different sizes and with different charges and their tendency to avoid each other and not to do so shows that the result of let’s call it the ‘electric’ or ‘zapper’ effect varies widely depending in the initial conditions. In supersaturated air it is pretty easy to get a condensation process going.
For me, it is difficult to rule out the effect completely. There is too much solid evidence (actual formation of CCN) and reasonable theoretical mechanisms for it. Extrapolating that to clouds is less secure, but not ruled out. An important consideration is taht GCR-CCNs are smaller and tend to last longer in a light-interactng state before coagulating into larger droplets.
I note Leif’s comment that the LIA ended with some contrary evidence but there are lots of other processes going on and it is a bit of a straw man argument to ask that the mechanism override all other large effects then say it failed to do so. I work with one of the top atmospheric particle people, a nuclear physicist, and he finds the cause-effect very convincing and teaches some of the physics to all his students. That there is any effect known to be true, the details are: how big is the effect, when, what overrides it and to what extent. I would not be able to argue convincingly that there is no effect – that GCR does not cause CCN formation. It obviously does and it is not a difficult effect to demonstrate, which Svensmark did with a pretty small budget.
The CERN result boiled down to, “The effect is there, it is bigger than we thought, don’t read too much into it, we need 5 years of funding to really know much for sure, we’ll get back to you.” Sounds familiar.
Crispin in Waterloo says:
August 21, 2012 at 8:50 pm
That there is any effect known to be true, the details are: how big is the effect, when, what overrides it and to what extent. I would not be able to argue convincingly that there is no effect – that GCR does not cause CCN formation. It obviously does and it is not a difficult effect to demonstrate, which Svensmark did with a pretty small budget.
As usual, it is all about relative size. Even Jupiter Shine has an effect. The question is if the GCR effect is large enough to be of any importance. And that is where it fails. The very fact that there is no general and overwhelming support for the effect [so we need not even discuss it – as we no longer argue whether the Earth is round or flat] is due to the other fact that the correlations are dubious, contradictory, and hard to agree on. Now, the GCR effect has attained the status of dogma which has a life of its own and in some circles may not be denied or doubted, quite on par with CAGW. Also, the hypothesis is a moving target, if it is not the low clouds, perhaps it is a special type of cloud, or maybe a kind of cloud not yet discovered. Science is full of hypothesis that have died a tortuous death, twisting left, right, and round trying to connect the dots where no connections [and at time even no dots] exist.
“””””…..docrichard says:
August 21, 2012 at 11:30 am
Ulric is mistaken when he says: “Clearly a negative feedback as the higher the cloud is, the colder it is, and the less it can potentially warm the surface, or keep the surface warmer”.
High clouds have a warming effect, and lower clouds tend to have a cooling effect. See http://www.climate4you.com/ > clouds > cloud types. …..”””””
Well doc, not only are those higher clouds colder, as Ulric said, but they also are much less dense in terms of water content, so there are fewer water molecules to absorb the LWIR emissions from the surface.
Also those clouds do not reflect particularly in the LWIR. In the visible, where we see them, they optically scatter. Water has only a 2% reflectance , in the visible and most of the solar energy containing spectrum. The point is that the scattered light is isotropic so it is widely dispersed, spatially, and much of it is simply lost to space.
In the LWIR water is highly absorbing. 1/e absorption length is about 1.25 microns at 3.0 microns, wavelegth, and certainly below 12.5 microns for the 288 K surface LWIR peakig around 10.1 microns. So those high clouds absorb; (so do the low ones only moreso because more water molecules) they do NOT reflect LWIR. Yes they do re-radiate, presumably at water IR bands. The liquid or solid water should also emit a thermal continuum radiation spectrum characteristic of the water Temperature, and that emission is also isotropic so widely scattered with half escaping upward..
We have to keep in mind that the principal source of WARMING LWIR ENERGY for those clouds, is about like an ordinary bottle of drinking water out of the refrigerator. It is nothing like a 100 Watt incandescent light bulb radiating at half the surface temperature of the sun, with a peak of spectral radiance, that is 10^5 times brighter than what the earth surface, or that bottle of water is radiating.
THAT is what is “warming” the cloud; high or low, and the even colder cloud, is what subsequently heats up the earth surface that was warming the cloud.
Those wispy high night time clouds, that warm you up over night, were actually caused by an even warmer daytime Temperature; and the warmer it was during the day, the higher the altitude of the dew point, so the higher the altitude of the night time clouds. It is pure bunk, that high clouds warm the surface; the warm surface caused the high clouds, and after sun down, the surface Temperature will fall; not rise, and it will be much colder in the morning. The Temperature never goes up at night, unless some warm air mass from some hotter place, moves in over night; which is convective heating, ot greenhouse gas or cloud heating.
Every single extra water molecule added to the atmosphere (CO2 as well), absobs additional incoming solar energy, which warms the atmosphere but cools the ground/ocean. And the atmosphere can’t heat the ground, because the conduction and convection are both in the wrong direction (rising), while the radiation is split half up and half down. The upward convection results in a downflow of cold air, which actually cools the ground..
Solar spectrum energy, that in the normal scheme of things gets deposited deep in the ocean (at least some down to 700 metres); but is instead captured by greenhouse gases H2O, O3, and CO2, NEVER EVER gets stored in the deep ocean. What increased emission in the LWIR from that warmed atmosphere, does reach the surface (only half) is absorbed in the top 50 microns of ocean surface, and largely just prompts increased evaporation; which is a cooling process, not a warming one.
See Wentz et al; “How much More Rain, will Global Warming bring?” SCIENCE, 7th July, 2007.
REPLY: Right, and much of the tropical cloud cover is Cumulonimbus. While there may be a correlation, I don’t know that cosmic rays help in tropical Cb formation more than say, increased aerosols. There are many factors to disentangle. – Anthony
increasing tropical CN with increasing temp indicates more enegy transport from surface higher in the troposhpere ie negative feedback. Increased cloud cover also produces further neg f/b
Higher Nimbostratus IIRC are deemed to negatively correlate with temps since their primary effect is on albedo. Less NS means more energy entering the system.
The second graph in this post suggests that NS is driving change and CN is the compensating feedback reaction.
So what is controlling Nimbostratus formation ….? Is there any hypothesis suffering a tortuous death that could possibly explain this?
Nobody believes Hansen’s ISCCP cloud data.
I would just throw this part of the data out and see what else the paper shows.
Philip Bradley says:
August 21, 2012 at 5:10 pm
“…the lack of a consistent correlation is persuasive that GCRs don’t seed clouds.”
I don’t think there has been a demonstration that a consistent correlation is lacking. Just perhaps not the one you’re looking for.
I think there is simply no supporting evidence or physics behind the claim that the global warming over the past century could simply be attributed to internal variability. Spencer’s hypothesis cannot account for numerous observed changes in the global climate (which are consistent with an increased greenhouse effect), does not have a known physical mechanism, and there are simply better explanations for interactions between global temperature and cloud cover.
McComberBoy @ur momisugly August 21, 2012 at 5:14 am
Garner was a race car hobbiest. Other actors, like Paul Neuman or Steve McQueen or Bert Reynolds, were race car enthusiasts. Even Jay Leno might be tossed in with the bunch. None, to my knowledge, ever ran a lap during any Indy. But drive race cars? You betcha! The owners loved the PR and the photo ops.
It’s apparent that clouds are getting a lot of attention lately. This paper along with Spencer-Braswell 2011, and also this one by Miller et al http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-11-00072.1 seem to be consistent that clouds are not represented well in climate models and inversely effect temperature. Whether a forcing or a feedback seems to now be a valid question. Maybe Spencer and Braswell were not as off base as the ridicule of them suggested?
Jane says
which are consistent with an increased greenhouse effect
Henry says
Hi Jane! I think you will find very few people on this blog who still believe in that fairy tale.
The first problem I encountered in my own investigation was that the ratio of maxima-means-minima is opposite of what you would expect it to be if it were indeed an increased GH effect causing warming of earth.
http://www.letterdash.com/HenryP/henrys-pool-table-on-global-warming
Clearly: it is from the top down: increasing maxima pushing up means and minima, if you look at it globally and not only at a few selected places on earth, like Las Vegas, that have special circumstances.
By measuring the speed of warming against time (acceleration/deceleration ) I figured that the maximum input of energy into earth occured in 1995.
http://www.letterdash.com/henryp/global-cooling-is-here.
Note that the graph for the decelereation of the warming is completely natural, like the traject of a thrown object.
From those results, it also looked that the warming cycle had started some 50 years before 1995.
However, like you I also doubt whether it is in the clouds./
Geewhizz, we can do a monkey puzzle survey and see/hear everyone’s most favourite explanation for the warming?
A. More CO2
B. less clouds/more sunshine due to GCR
C. Increase output of energy by the sun
D. Other human activities, e.g. removing trees, removing snow, adding heat by driving/burning fuel, etc
E. Sun cycle activity related to the movement of the major (tropic) cloudbanks either more towards the equator or more towards the poles
F. sun cycle activity related to a small variation in UV light from the sun, which affects the amount of ozone production in the stratosphere (a certain type UV light converts oxygen into ozone); ozone re-radiates a lot of high energy sunlight to outer space and if there is less of it allows more energy in.
Take your pick. You can also chose a combination. I’d be interested to hear all the choices here on this blog?
‘Andrew Girle says:
August 20, 2012 at 11:03 pm
Interesting. Correct me if I mis-remember, but doesn’t one of the foundations of CAGW suggest that as it warms there will be less cloud and thus less rain? No references, just a hazy recollection.
What I think now becomes important is what comes first – less cloud due to natural variation forcing temperature rise; or temperature rise due to the dastardly CO2 forcing less cloud. And at what point do the feedbacks (from either side of the argument) kick in?
‘
*****************
you are correct in your recollection. This is really an assumption made by lacis and hansen (et al) from a late 1980s vintage paper that they use now as a “fact”. There are several problems with the basic concept which is higher temperature reduces cloud cover despite there being more h2o vapor available to make clouds.
as for the problems, first off, that would mean the Earth only can have a cloud cover of no more than around 60% because when T drops, cloud cover drops and when T rises, cloud cover drops. There could be no 70, 80, 90, or 100% cloud cover possible at any T. Second, there could be no stable operating point to limit T from feedback if this were true. In other words, a small increase in T would decrease the clouds and create a large increase in T – totally unstable positive feedback which would drive the T to the upper rail and keep it there. Third, clouds form when lighter, (and warmer due to IR absorption) h2o vapor rises up through the atmosphere where it encounters lower T emperatures and the RH reaches about 100%. This mechanism doesn’t go away just because there is a small change in T at the surface as there will be an altitude where clouds will form if there is h2o vapor present and it is able to reach that altitude. Fourth, this idea from the hansen paper is one of these things invented to provide a reason why there might be catastrophic positive feedback in order for there to be the possibility of catastrophic warming. It’s not part of a scientific hypothesis to an explain an observed or calculated phenomenon but rather is a hypothesis to promote an assumption (and an agenda). Finally, after observing albedo (finally) for a number of years, it was observed that it has varied by enough to be the equivalent of 2 or 3 co2 doublings and has recovered from the excursions, despite its changes and the changes in T related to it. As stated above, if cloud cover variations come form T, we’d be in an unstable equilibrium and would have slipped off of it, never to recover.
While it is possible to have a two way street – like co2 can affect the T and the T for the oceans can affect the co2 absorption in the oceans so that more co2 warms and warmer oceans emit more co2 due to less ability to absorb due to warmer T, there can only be one net result. There can be a net positive feedback or a net negative feedback, or no effect due to perfect cancellation. If cloud cover has a net effect, then it can either be only net positive or it can only be net negative.
If it is net positive, then there is no stability or regulating effect possible and T will vary more. If it is net negative, then T variations will be less than it would have varied without the presence of clouds. Considering that the presence of clouds reduces incoming solar energy at the surface and slows the evaporation cycle, it only makes sense that it is a net negative feedback mechanism that provides control and stability to the Earth system.
Note that these ideas are simplified and different types of clouds have different effects and they have different timings of formation and dissipation and that there is a 24 hr cycle of incoming power from the sun that varies over latitude and year . Also note that many factors affect both clouds and albedo of those clouds. Changing droplet sizes of the particles can change the albedo or reflectivity of the cloud without the need to change the coverage fraction. This is the Achille’s heel of the CAGW movement and of the majority of attempts at measuring sensitivity to forcings which show wide variations in results and seem to support the possibility of catastrophe.
It is clear that whatever is warming the planet, must be driving weather system changes in order to do that. Temperature change is a result of weather system change. You cannot get around that statement to talk about CO2. So whatever is being touted as the temperature driver must be “joule” capable of that feat (affect weather system patterns over the long term) and make a fairly continuous long-term effort to sustain those weather system changes to make an anomalous difference on the temperature trend.
Here is the reason anthropogenic CO2 cannot be the driver. The anthropogenic portion of the increase in CO2 ppm has not done its magic on water vapor (water vapor must anthropogenically increase in order to cause more heat to be held at the surface in order for the CO2 theory to work). Water vapor increase is a weather-related event. Anthropogenic CO2 does not have the joules necessary to cause weather system changes that would lead to increased water vapor that would lead to global warming. End of story.
Spencer-Braswell-JGR-2011 is available from “Another Paper Featuring Conclusions Unfavorable to AGW Assassinated” (http://www.conservativecommune.com/2011/09/another-paper-featurng-conclusions-unfavorable-to-agw-assassinated/), at http://www.drroyspencer.com/wp-content/uploads/Spencer_Misdiagnos_11.pdf
”
Paul H says:
August 21, 2012 at 1:28 am
Before judging whether clouds have cooled or warmed the planet one needs to consider the effects they will have on all relevant parts of the electromagnetic spectrum. Less clouds should mean less incoming short wave radiation, which people have jumped on here, but less clouds should also mean more outgoing longwave radiation. Until someone performs the relevant radiative transfer calculations it is premature to be saying anything about whether this supports Roy Spencer’s cloud hypothesis.
”
Simple values give us averages of what’s going on. The surface average is around 288.2k and radiates around 390 W/m^2. The incoming average solar incomming is around 341 w/m^2 and the albedo is around 0.3. That means we’ve got about (1-0.3)* 341 =~ 239 w/^2 being absorbed by the Earth/atmosphere. For a rough balance, that means around 239 W/m^2 must be radiated from Earth. 239/390 = 61% of the surface emissions escape (or are reradiated from the atmosphere), leaving about 390-239 = ~ 151 w/m^2 being trapped in the atmosphere. Of that, about 2/3 is ghg absorption with roughly 2/3 being h2o vapor and 1/3 being co2 (60 & 30 W/m^2), and 1/3 or about 50 w/m^2 is cloud absorption, etc. A blackbody at 255K would emit about 239 w/m^2 and 288-255 = 33 deg C which is the T increase due to that ~151 W/m^2 of absorption. 33/151 = ~ 0.22 deg C rise per W/m^2 overall average. Also, we’ve got about 0.62 cloud cover (62%) and an albedo contribution of around 0.22 for clouds and atmosphere versus around 0.08 for surface albedo.
Clouds will radiate a continuum at their cloud top T and it will be above most h2o vapor and above lots of the other ghgs and at lower temperatures so that emission lines are narrower when it comes to additional outgoing absorption.
Note too that radiative programs like modcalc will show a clear sky radiation rate near 270 W/m^2 which is significantly above the average 239 W/m^2 needed for balance. If you eliminated clouds, the surface would have to cool to reduce the output from 270 to 239 w/m^2 and that corresponds to a reduction of 31 w/m^2 escaping, reducing the T by almost 6 deg C to 282k assuming the albedo didn’t change. Allowing about 14w/m^2 for atmospheric scattering and eliminating cloud albedo, one would have around 41 w/m^2 of albedo ( a =0.12) and incoming solar average of 341 – 41 = ~ 300 w/m^2. Now we need a new balance of 300 w/m^2 rather than 239w/m^2 so our clear skies 270 w/m^2 radiation output is now low by 30 w/m^2. Applying that to surface T using again Stefan’s law, our clear sky emission of 270 W/m^2 + 30 W/m^2 gives us 300W/m^2. The surface would need to heat up by enough T to emit an additional 30 w/m^2. Starting with the current 288.2k with 391 w/m^2 and adding 30 w/m^2, we get a new surface T of 293.5k which is a warming of 5.3 deg C.
Hence, taking away clouds actually increases the T. That must mean that adding cloud cover must reduce the T, at least in our current condition of no massive lower latitude glaciation.
This paper does a decent job of examining temperature response to ENSO events. It further testifies as to the nature of temperature trends. Anomalous trends are more than likely a weather system pattern change. The AGW theory must address whether or not anthropogenic CO2 is capable of affecting ENSO parameters to the extent that it can, for decades, drive these parameters in a direction that results in positive temperature trends.
http://www.esrl.noaa.gov/psd/csi/pubs/docs/JCLI3944_rev11.pdf
docrichard says:
August 21, 2012 at 6:08 am
….Simple physics teaches us that less cloud is to be expected in a warmer atmosphere….
_____________________________
ERRrrr, I do not think so.
Warmer atmosphere will cause more cloud cover due to increased evaporation. I did a quick and dirty look-see along the Eastern Seaboard of the USA a few years ago to check out my observations from living in several places in the USA and Willis’s Thermostat Theory. The number of summer storms decreases as you move north. Going from ~ 20 per month (July & August) in Florida to less than 10 per month north of Raleigh NC.
This was when the Jet Stream was still zonal and not the more meridional jets we are seeing now. At that time the wind was consistently out of the west. This means the towns I looked at (~ 100 to 200 miles inland) were in the rain shadow of the Appalachians. The last couple of years the winds coming from all directions so the ocean moisture is coming more into play and we are seeing more rain. Despite the screaming headlines this has been a very soggy summer. I can still dig fence posts in my clay soil. Normally even the tractor can not get through the baked brick soil in the summer.