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:
Rikard says:
August 21, 2012 at 5:03 am
Re Leif
“Thanks for engaging though, you´re one of the few warmists I still find it worth listening to ;-)”
Not sure Leif is a warmist. Read this:
“Leif Svalgaard says:
June 18, 2011 at 4:15 pm
I don’t think that your analysis and Bart’s will lead to savings of billions of dollars and any lives saved, because the AGW threat is political and not scientific.”
or this:
@-Leif Svalgaard says: Re-(The issue discussed is about model predictions being treated as gospel and policy being made on that.)-
“That is not the fault of the modelers. That is the fault of people you have voted for. I agree that the policy is stupid, but people deserve what they vote for. That you don’t want to spend billions is understandable, but elected politicians squander billions on things like war and ill-advised subsidizes, so what’s the difference? You take your displeasure as input to your assessment of science, and THAT is wrong.”
well, Mr. Watts introduced Svensmark to the topic, Leif just replied, didn’t he?
From another thread Leif thinks that CO2 doesn’t warm the troposphere much but that it does cool the stratosphere (along with CFCs) and that therefore the poleward shifting jets were due to CO2 and CFCs.
That enables him to deal with the now equatorward shifting jets by saying that the reduction of CFCs is offsetting the continuing effect on the stratosphere of more CO2 whilst remaining a sceptic as far as the effect of CO2 on the troposphere is concerned.
Unfortunately that does not explain the cyclical shifting of the jets fom MWP to LIA to date.
I think he is wrong, that the sun is the primary culprit and that the effects of CFCs and CO2 on both stratosphere and troposphere are minute compared to the natural solar induced changes.
If I have misunderstood then no doubt Leif will clarify.
Stephen Wilde says
http://wattsupwiththat.com/2012/08/20/spencers-cloud-hypothesis-confirmed/#comment-1062139
Henry says
well said. we know what is happening, don’t we?
1) by analysing the distibution of results for maxima, means and minima, I observed that the warming was due to more heat getting slammed into the big (SH) oceans…
http://www.letterdash.com/HenryP/henrys-pool-table-on-global-warming
2) by measuring the speed of warming against time (acceleration) I figured that the maximum input of energy into earth occured in 1995.
http://www.letterdash.com/henryp/global-cooling-is-here.
From those results, it also looked that the warming cycle had started some 50 years before 1995.
3)Therefore the time periods analysed of the clouds is a bit wrong. Notice that in the graphs for Africa and Australia/Oceania there is a clear decreasing trend until 1995 and an uptrend from 1995. (SH will show change first. In S-America they chop too much wood so they do not know what clouds look like)
For Eurasia it was also going down from 1971 but it looks like flat from 1995.
4) there appears to be a 100 year weather cycle causing 50 years of cooling followed by 50 years of warming that coincides with solar activity. It must be due to the interaction of UV and oxygen in the upper atmosphere and the formation of ozone.
http://wattsupwiththat.com/2012/08/13/when-will-it-start-cooling/#comment-1061453
Also see “A Primer on Our Claim that Clouds Cause Temperature Change”
September 3rd, 2011 by Roy W. Spencer, Ph. D., at http://www.drroyspencer.com/2011/09/a-primer-on-our-claim-that-clouds-cause-temperature-change/
“The IPCC claim is that clouds will change in response to warming in ways which magnify that warming (positive cloud feedback), but by an unknown amount. All of the 20+ climate models tracked by the IPCC exhibit from weak to strongly positive cloud feedbacks.”
“But we claim (and have demonstrated) that causation in the opposite direction [cloud change => temperature change] gives the illusion of positive cloud feedback, even if negative cloud feedback really exists. Thus, any attempt to estimate feedback in the real climate system must also address this source of “contamination” of the feedback signal.”
“It would be difficult for me to overstate the importance of this issue to global warming theory. Sufficiently positive cloud feedback could cause a global warming Armageddon. Sufficiently negative cloud feedback could more than cancel out any other positive feedbacks in the climate system, and relegate manmade global warming to the realm of just an academic curiosity.”
“Cloud feedback happens rapidly, in a matter of days to a few weeks at the very most, due to the rapidity with which the atmosphere adjusts to a surface temperature change. It this paper, we even showed evidence that the peak net radiative feedback (from clouds + temperature + water vapor] occurs within a couple of days of peak temperature.”
“I have more extensive evidence now that the lag is closer to zero days.”
http://www.halesowenweather.co.uk/cet_sunshine.htm
“CET ANNUAL MEAN TEMP VS ANNUAL SUNSHINE HOURS
Overlaying annual mean temperatures with annual sunshine hours for the period 1929 to 2010, an increase over the years can be seen in each, but also evidence for the link between them becomes apparent, since they often rise together or fall together.”
I think the distinction is finer than that, and is at the ‘margins’, that is to say, there are small percentage changes, perhaps the Cb begins to form seconds earlier, perhaps the total precipable water (potential) rain amount is increased a small percentage …
.
Thanks Henry.
I share your conclusion but have a slight problem with some of your timings.
Nonetheless this is not a precise science as yet and the ENSO signal does interfere with the solar signal.
If global warming is not producing additional atmospheric moisture as one of the cardinal feedbacks predicts what does this say about the models?
Dang ! All these years I was sure that I got colder, when a cloud went between me and the sun, so I was in a shadow zone; but I never carried a thermometer around to prove it was colder.
Just think; I could have published my seat of the pants observations in some peer reviewed journal, and nipped all this costly controversy in the bud. Well as they say; You snooze, you lose !
Right on Dr Roy; you pegged it. (It appears, maybe just possibly consistent with the new observations.
So from the first graph, North America cloud is going nowhere, but Canada and USA is going south cloudwise, so what else is in North America, that must be having a big increase in cloud ?
Well I suppose it must be Mexico. I did once describe here at WUWT actually watching clouds form and grow out of nothing over the Baja Peninsula, adjacent to the Sea of Cortez, while I was out fishing.
See, another missed research grant opportunity; but it must be true; Mexico is all clouding up. As I recall, I even explained just how I thought it all worked; but noted I am NOT a meteorologist, so Anthony probably got a good laugh out of my silly idea.
I should do more fishing, and take a thermometer with me, plus my fisheye all sky lens. I think it is better to measure cloud cover from UNDER the cover where it counts, than looking from the top; and the fishing is better underneath as well. The Nyquist problem is somewhat formidable when measuring clouds; but nobody in climatism pays any attention to sampled data theory anyhow; see for example, the Yamal Charlie Brown Christmas Tree fiasco.
MAK says:
August 20, 2012 at 11:25 pm
“Leif: “Except that as solar activity has generally decreased [hence cosmic ray intensity increased], Svensmark’s hypothesis would predict an increase in cloud cover. So, no need to look there.”
Tropical cloud cover seems to be increasing and also seems to (inverse) correlate quite well with cosmic ray intensity.
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”
Just a casual observation of the charts, but they seem to indicate that clouds have NOT decreased during the past 10 or so years during which temperature has also NOT increased, not attempting to speak to WHY clouds are increasing or decreasing, only that this small sample of the recent past seems to fit the theory relative to clouds and temperature,
Maybe I got that Canada/USA thing backwards. Mexico is getting uncloudy, while the USA/Canada cloud is filling in for their lack of cloud.
Tim Folkerts says:
August 21, 2012 at 6:03 am
* Where have all the skeptics gone??? There are so many questions to be answered, yet any report that supports the desired conclusion seems to be given a free pass on skepticism.
This happens all the time, it is called Confirmation bias.
Harold Ambler says:
August 21, 2012 at 6:52 am
Leif, do you wish to retract your claim that a paper regarding cloudiness over land can be used to critique Svensmark?
My claim was that the paper under discussion does not support Svensmark. Do you think otherwise [see my reply to Tim]? And the data I linked to is the global cover which you may recall is mostly ocean.
Stephen Wilde says:
August 21, 2012 at 7:42 am
From another thread Leif thinks that CO2 doesn’t warm the troposphere much but that it does cool the stratosphere (along with CFCs) and that therefore the poleward shifting jets were due to CO2 and CFCs.
You still don’t get it. The stratosphere responds to the jets, not the other way around.
docrichard says:
August 21, 2012 at 6:08 am
“It is clear from the data that cloud cover is inversely proportional to global temperature.”
Perhaps Svensmark needs to rethink his theory. Is it possible that more cosmic rays would speed up the velocity of the water cycle and mean that more compact precipitation zones (less overall cloudiness) would serve to maintain the heat balance?
Quick fix:
“cosmic ray insolation intensity increases”
“Insolation” comes from the sun (our sun). Cosmic rays come from (notionally) exploded suns.
Perhaps change it to
cosmic ray flux intensity increases
+++++++++++
Please remember there are lots of cosmic rays that originate from the sun. The galactic cosmic ray flux is a subset of all cosmic rays. The atmosphere is indiscriminate.
Come on everyone. Peter Stroud is correct when he says:
“This research, Dr Spencer’s work and the general increase in climate studies all reveal an important fact. That the climate is far too complex to be covered by by just one hypothesis. Regardless of what Hansen and the other IPCC supported scientists say. Keep up the good work.”
If we have learnt anything at all it is that the “one hypothesis” paradigm, with respect to climate, is a million miles away from the truth. The notion that CO2 is THE preponderant cause of climate changes ought never to have been entertained in the first place. We are still feeling our way when t comes to an even half decent understanding of the Earth’s climate.
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?
Thankyou Andrew. Decreased cloud cover could be what the climate clowns call “positive feedback.” Score that round to the warmist corner.
What about looking at aerosol coverage and create a mask of areas that usually have types that would compete with aerosols produced frame the proposed cosmic rays effect. Then look at changes in albedo.
Stephen Wilde says:
August 21, 2012 at 6:31 am
Is that the right way round ?
-Yes it is. The graph is confusing, because it places the low level cloud (blue) above the high level cloud (red).
Stephen Wilde says: We can ignore CO2 for the moment because this has all happened before.
– This is not a safe argument in a multi-factorial system.
It is like saying, “I had a cough for 6 weeks when I was a non-smoking child, therefore my present cough has nothing to do with the fact that I now smoke”.
@Robbie
“It looks like the authors conclude the opposite: It is climate change which causes cloudcover and cloud properties to change/evolve and not what is being speculated here. So in fact what EW2012 are saying is that cloudcover changes are a feedback of climate warming.
Dr. Spencer is claiming the opposite of what Eastman & Warren are saying.
Who is right and who is wrong is the big question?”
++++++++++
Well I think it would be correct to remember that the core claim for ‘scary warming’ from CO2 is positive feedbacks attributed in models to H2O vapour increasing in the absolute sense – increasing specific humidity because of a drop in relative humudity caused by CO2 forcing. Is this not so? Is this not the reason for the claim that doubling of CO2 will lead to +3 Deg C in global temperature? I believe it is because it has been cited very many times and is in the IPCC reports.
So let’s look at the facts: the global temperature rose significantly from 1976 to 1995 or 98 depending on who you ask, but not since then. The specific humidity declined during that time and the cloud cover also decreased (it could hardly increase with less water vapour available).
>“Climate observations and models suggest that cloud properties have changed and will continue
to change in a warming climate.
Well they have changed, but it has not been because of increasing specific humidity, and that is the core reason for a claim for water feedback effects from a CO2-warmed world, isn’t it? Am I missing something here? Where is the positive feedback that results in an increased the specific humidity? The specific humidity has dropped with rising CO2, not increased! There seems to be no positive CO2, water vapour feedback, temperature rise at all. It looks neutral or negative no matter which way you slice it. Since 1995, the specific humidity dropped with basically no change in temperature. The CO2 level is much higher with no change in temperature, and a forecast specific humidity ‘feedback’ rise that has not materialised. It seems to me the postulation of a CO2-forced H2O ‘feedback law’ is abrogated.
>Changes are likely to be seen in cloud amount, height, thickness, geographical distribution, and morphology.
Well, that’s easy to say isn’t it? But is does not address the core of the theory at all.
>Widening tropical belts and warming polar regions may be causing a poleward displacement of Earth’s jet streams…
Or Vice Versa, driven by the positive or negative AMO and PDO. Which is the effect? Which the cause? There is a body of thought that says the jet stream paths are highly (significantly) affected by solar events, or lack thereof. At least the solar effects correlate with the observations.
Unless some additional H2O vapour can be located in the atmosphere in an world with increasing CO2, with or without a temperature change, the ‘positive feedback’ conjecture is invalidated. As there is an equally valid and physics-based claim for negative feedbacks, and as the evidence supports it, one can confidently say there can be no empirically-based consensus that CO2 induces a positive specific humidity feedback effect nor a positive feedback temperature increase resulting from a CO2-induced increase in atmospheric water vapour content.
Because it just ain’t so.
Stephen Wilde says: “Warming has to be caused by more solar energy getting into the oceans so the clouds must reduce first. The sun must cause a change in the global air circulation that reduces clouds when the sun is more active. Hence latitudinally shifting jets with increased zonality and wider tropical air masses at a time of active sun”.
– To be clear, you are supposing that when the sun is more active, jets streams will shift towards the poles, and/or clouds cover will consequently be reduced.
This is a testable hypothesis, since there should be a positive correlation between solar activity and cloud cover.
Datasets on both of these must be available, possibly on climate4you.
Crispin in Waterloo says:
August 21, 2012 at 8:38 am
Please remember there are lots of cosmic rays that originate from the sun. The galactic cosmic ray flux is a subset of all cosmic rays.
Actually not, and certainly not of the energy [above 10 GeV] that Svensmark claims are needed for his theory.
Steinar Midtskogen says
August 21, 2012 at 12:08 am
“If temperature rises, relative humidity drops and you get less clouds. So what comes first, higher temperatures or less clouds?”
A temperature rise comes first, but produces higher clouds, in particular higher amounts of mid level clouds but lower amounts of low level clouds. 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.
Is there anyone out there who knows where I can download data of monthly cloud cover over different regions which also include last year?
The reason I’m asking is because over the last months I have experimented with an Artificial Neural Network software I’ve written in which I look for correlations in climate data. I’m especially interested in finding climate correlations in relation to cosmic data. That is solar wind data, galactic cosmic ray data and correlations to magnetic variations.
The data I’m using is data that are available and downloadable on the Internet.
I’ve looked at correlations to the global temperature from satellites and from GISS.
I’ve written about the global temperature data from satellite data HERE.
The result I got was surprising to me, because what I found was that there were high correlations between the solar wind indexes and the global temperature from the satellite. In fact too high!
What I now think is that this result is as a result from an artifact in the satellite recording. It can be from variations in the satellites drag, from contamination caused by variations in the ionization on the upper atmosphere or the variations in the number of protons from cosmic rays could also affect the detector in some way.
Right now I’m doing runs looking for correlations to the ENSO index.
There are two reasons for doing this. One is that I’m interested to find out correlations of forcing factors to the climate. The other is as an engineering interest as I use the neural network to search for correlations on a chaotic non linear system in which the different factors are intercorrelated in a complex fashion. In such a system it is difficult to find out the underling factors by using FFT analysis or by utilizing regression analysis, simply because there are too many underlining factors and time lags.
My belief is that by using Neural Networks in the way I have used by looking for statistical correlations, it is possible to overcome many of these constrains when one is dealing with complex intercorrelated chaotic non linear systems. I think that correlations calculated from Neural Networks in engineering and physics is under-used.