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:
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Leif Svalgaard says:
August 21, 2012 at 4:34 am
“Top graph of http://climate4you.com/images/CloudCoverAllLevel%20AndWaterColumnSince1983.gif
shows that Water content has been dropping too.”
Please note that the step-like change in atmospheric water content 1998-1999 may be related to changes in the analysis procedure used for producing the data set, according to information from ISCCP. The cloud cover data, however, should not be affected by this.
Source: http://www.climate4you.com/
docrichard says:
August 21, 2012 at 9:20 am
“This is a testable hypothesis, since there should be a positive correlation between solar activity and cloud cover”
Already demonstrated by the cloud data referred to here and elsewhere. In fact the data suggested my hypothesis rather than the other way around.
The decline in global cloud cover during the late 20th century correlates with more zonal jets and high solar activity.
Then when solar activity dropped from around 2000 the jets became more meridional and clouds began to increase again.
I’m just waiting for enough time to pass for others to realise that it is a consistent phenomenon (or for it to be rebutted).
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.
Laif replies:
“You still don’t get it. The stratosphere responds to the jets, not the other way around.”
So what shifts the jets if, as you say, CO2 doesn’t warm the troposphere much ?
And don’t refer to the oceans or volcanoes because they don’t reproduce anything on the timescale of MWP to LIA to date.
Furthermore the evidence you produced only referred to a cooling of the stratosphere in the region of the shifted jets and NOT the stratosphere as a whole.
So, I think the one who fails to ‘get it’ is you.
Also, Leif, you said that the stratospheric cooling effect of the CO2 was being offset by the stratospheric warming effect of reduced CFCs and now you suggest that the stratospheric cooling was caused by the shifting jets.
Just admit that your narrative is an utter mess and give some credit to those of us who are creating narratives that fit the facts.
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.
This explains why in a warming world, although clouds become less in quantity, their quality tends towards a positive feedback.
docrichard says:
August 21, 2012 at 11:30 am
“High clouds have a warming effect,”
Just how exactly?
Ulric Lyons says:
“High clouds have a warming effect,”
Just how exactly?
– http://www.skepticalscience.com/clouds-negative-feedback.htm
Stephen Wilde says
I share your conclusion but have a slight problem with some of your timings.
Henry says
I am very open to ideas on time scales.. My data suggests there was a change in signal (from warming to cooling) in 1995 and it is now confirmed by another party…
nevertheless this other party seems to think that the solar cycle itsself should be measured in 22 years and not 11 years. In which case we are still positive (warming) , that is, if we go by evaluating all data from 1990-
you tell me
what must I do?
Adam Gallon says:
August 21, 2012 at 8:11 am
Note the pattern change from about 1960 to 1990. This long term effect shows that it is too simplistic to think only that less cloud causes warming (or vice versa). The important point of the abstract is this:
Stephen Wilde says:
August 21, 2012 at 11:02 am
“You still don’t get it. The stratosphere responds to the jets, not the other way around.”
So what shifts the jets if, as you say, CO2 doesn’t warm the troposphere much ?
I refer to the previous thread. There is no need to try to high-jack the present thread. And perhaps it would be good if you tone down your rhetoric a bit.
@Leif
Thanks. I am interested in your take on the energy needed.
>>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.”
Do you agree with the effect (at all) and if so, what do you think is the required energy level to produce nucleation?
The reason I ask is that I visited a demonstration given by the Perimeter Institute here in Waterloo and I recall the energy to have been much lower than 10 GeV. Perhaps Svensmark is looking for a certain level of effect rather than ‘nucleation at all’.
Perhaps one of you has a chart of the energy:response that points to some minimum energy level, or perhaps at different levels of charge in the atmosphere responding differently.
Lets see, low level clouds are increasing, which trap greenhouse heat, and high level clouds reflect in back into space to cause cooling. So these observations should indicate a warming trend according to the AGW crowd, but it is not.
So what are have they left out of their immaculate models?
docrichard
Observations appear to show that high and medium clouds decreased when temperatures were rising and increased when temperatures stopped rising around 2000.
Low clouds did the opposite.
Therefore how can you say that high clouds have a warming effect and low clouds have a cooling effect ?
High clouds reflect a lot more solar energy back out to space than low clouds which is consistent with the albedo changes measured by the Earthshine project.
It is true that low clouds insulate better than high clouds but in energy budget terms insulation is a less powerful effect than reflection because insulation merely delays energy loss whereas reflection denies energy to the system altogether.
The truth is that a solar induced reduction in high and medium clouds allowed more energy in so the system warmed. In the process low clouds increased.
Since about 2000 a solar induced increase in high and medium clouds allowed less energy in so the system is now cooling. In the process low clouds have decreased.
Leif said:
“There is no need to try to high-jack the present thread.”
This thread is about global cloudiness which is linked to jet stream behaviour and the temperature of the stratosphere.
If you can say how the stratosphere as a whole (not just in the region of the jets) came to cool whilst the sun was active that would be helpful. Especially since it is no longer cooling with the less active sun.
I say the sun did it.
Do you say it was CO2 and / or CFCs and /or shifting jets or something else ?
Any ideas that fit the facts would be good for this thread.
Crispin in Waterloo says:
August 21, 2012 at 11:45 am
Actually not, and certainly not of the energy [above 10 GeV] that Svensmark claims are needed for his theory.”
Do you agree with the effect (at all) and if so, what do you think is the required energy level to produce nucleation?
The data does not support the theory, e.g.
http://www.purdue.edu/discoverypark/climate/assets/pdfs/Relationship%20of%20Lower-Troposphere%20Cloud%20Cover%20and%20Cosmic%20Rays_%20An%20Updated%20Perspective.pdf
Svensmark has always maintained that energy higher than 10 GeV is needed. Regardless of other considerations, he has to maintain that, because at lower energies the long-term changes of the Earth’s magnetic field falsifies his theory.
First, I appreciate reading WUWT daily.
Second, as a non-climatologist, I look at all reporting regarding the issue
of global stewardship.
The numbers that relate to de-forestation have intrigued me for some time.
I vividly recall driving across the country in 1971 to stage for Vietnam deployment.
In the early morning hours, my wife and I could see clouds being born!
As the spring morning’s temperatures rose, you could see the mist coalesce and
form defined clouds above the forests. By 11 AM, the clouds flew the nest, caught the winds
and moved along.
The following is an exerpt of a 2010 U.N. report on global de-forestation. It was
interesting that the rate of de-forestion seemed to match the cloud loss report.
Deforestation imperils biodiversity, but some trends encouraging – UN
http://www.un.org/apps/news/story.asp?NewsID=36330&Cr=fao&Cr1=&Kw1=deforestation&Kw2=&Kw3=
4 October 2010 –
High rates of deforestation and degradation of woodlands continue to threaten the world’s forest biodiversity, the United Nations Food and Agriculture Organization (FAO) said today, but pointed out that there is a positive trend towards the conservation of forests in many countries.
Globally, around 13 million hectares of forests were converted to other uses – including agriculture – or were lost through natural causes each year between 2000 and 2010, according to the findings of FAO’s Global Forest Resources Assessment 2010. The trend of forest loss has declined from around 16 million ha per year during the 1990s, the report said.
The report, the most comprehensive assessment of the state of the world’s forests ever undertaken, was released today at the start of the latest biennial meeting of the FAO’s Committee on Forestry and World Forest Week, in Rome.
More than one third of all forests are classified as primary – showing no visible signs of human intervention. Primary forests, in particular tropical moist forests, include some of the world’s most species-rich and diverse ecosystems.
Primary forests account for 36 per cent (1.4 billion hectares) of the world’s forest area but their area has decreased by more than 40 million hectares – at a rate of 0.4 per cent annually – over the past 10 years
Stephen Wilde says:
August 21, 2012 at 12:03 pm
“Observations appear to show that high and medium clouds decreased when temperatures were rising and increased when temperatures stopped rising around 2000. Low clouds did the opposite.”
In fact from 1994 to 2006 medium level cloud amounts increased, and low level cloud amounts decreased: http://climate4you.com/images/CloudCoverAllLevel%20AndWaterColumnSince1983.gif
Stephen Wilde says:
August 21, 2012 at 12:03 pm
“Observations appear to show that high and medium clouds decreased when temperatures were rising and increased when temperatures stopped rising around 2000”.
– Sorry – which observations? I am looking at the climate4you pages. As you know, climate4you is not a “warmist” site, and in any case, it simply presents the data.
Observations show that cloud cover decreases in a warmer atmosphere. Spencer says above that “clouds are earth’s sunshade”. Cloud albedo therefore decreases in a warming planet – a positive feedback. Cloud quality changes towards heat trapping – again, a positive feedback. These findings may or may not support Spencer’s hypothesis that cloud changes are the cause and not the effect of temperature changes, but they certainly do undermine the hypothesis that clouds have a net negative feedback.
“In fact from 1994 to 2006 medium level cloud amounts increased, and low level cloud amounts decreased: http://climate4you.com/images/CloudCoverAllLevel%20AndWaterColumnSince1983.”
Ok, I accept that refinement.
Fits in with HenryP’s point that the inflection point was 1995 or thereabouts rather than 2000 which was when I first noted the jetstream changes from my own observations.
The low and medium clouds appear to have been affected by the solar changes a few years earlier than the high clouds.
I think 1995 qualifies as ‘around’ 2000 at a pinch.The important thing is the inflection point in all three levels whilst the sun was declining from the peak of cycle 23.
Stephen Wilde says:
[A positive correlation between solar activity and cloud cover is] already demonstrated by the cloud data referred to here and elsewhere. In fact the data suggested my hypothesis rather than the other way around.
…I’m just waiting for enough time to pass for others to realise that it is a consistent phenomenon (or for it to be rebutted).
– sorry, your reference to data “here and elsewhere” does not amount to a demonstration. If there is a robust relationship between solar activity, cloud cover and jet streams in the way you are speaking of, please either give a reference to it, or get the datasets and create a relationship that you can show us.
HenryP asked
“what must I do?”
I’m happy with the inflection point in 1995 but I thought it would have been a bit later. The medium and low cloud data supports you.
Pre 1995 I think you have insufficient data for accuracy and the interaction between PDO phases and low cycle 20 might have skewed the numbers anyway.
Best thing is to wait and see how the data plays out through the rest of cycle 24 and into cycle 25.
I can’t make any progress with Leif and many others unless things go as we expect.
The low cycle 24 is a great help for diagnostic purposes but there are still too many reasonable points that others can choose to discount the connections as we see them.
I think the position will be resolved naturally in a few years provided the sun stays quiet.
@docrichard
August 21, 2012 at 12:35 pm
From the NASA link on your link:
“On the other hand, high wispy clouds drifting by are less refreshing. Such clouds cast meagre shadows and, because they are themselves cold, they trap heat radiated from the planet below. The air temperature near the ground might actually increase.”
It would make sense that completely clear sky conditions would lead to the highest near ground daytime temperatures, think desert. And I don’t see how “wispy clouds can trap much heat, and as they are cold, that in itself proves that they don’t. All they can do is reduce insolation at the surface, and provide virtually no night time warming.
Well I’m sorry Ulric, but that’s what we read – from both sides of the divide. If you are interested in it, why not do an in-depth study of the basis for the general statement “High clouds warm, low clouds cool”.
@Rober Doyle
Do you have any comment on the increase in forestation of the NE USA over the past 50 years as people left the farms and they returned to mixed woodlands? The area involved is very large (hence the huge recovery of the deer population). Dr Bill Mollison certainly supports the view that trees create precipitation though he is always careful to point out that dewfall from trees can be large, in some cases be larger than the rainfall.
Dr St Barbe Baker is another friend who supported the water vapour harvesting by trees idea and helped create the first giant sequoia sanctuary in the 1920’s. He initiated the “Save the Redwoods” campaign in California. It had to be large enough to maintain the microclimate (9000 acres originally, then 20,000).
http://www.motherearthnews.com/nature-community/environmental-leader-richard-barbe-baker.aspx#ixzz24DSWG3HG
Both of these scientists were preaching from the same trees = clouds+rainfall gospel. St Barbe Baker often talked about reclaiming deserts by planting hardy trees (like peaches) at the edge and working in. Mollison speaks of greatly increasing rainfall with strips of trees about 80 km apart. If there is a clear relationship between tree cover and cloudiness (it would have to be regional to be believable) this deserves close attention because they are a major source of water vapour – 2.5 tons per day in the case of each mature Sequoia. Are these clouds cooling? Maybe there is a demonstrable correlation between increasing tree cover and declining temperatures in the Eastern US (perhaps during some seasons only). They absorb a lot of sunlight.
<iPerhaps 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?
More cloud seeding elements result in more and smaller droplets. which cause the clouds to be more persistent. That is, take longer to precipitate out. We see this in the Weekend Effect when lower levels of cloud seeding aerosols at the weekend result in increased precipitation, of the order of 20%.
And as others have commented above, deforestation is likely playing a significant role in decreasing clouds. Forests impede runoff compared to agricultural land and return water to the atmosphere by transpiration. Here in Australia, a large tree will transpire in excess of 10,000 litres per annum.
And no one has mentioned contrails, which is cloud seeding on a global scale.
anengineer says:
August 21, 2012 at 12:02 pm
“Lets see, low level clouds are increasing, which trap greenhouse heat, and high level clouds reflect in back into space to cause cooling. So these observations should indicate a warming trend according to the AGW crowd, but it is not.”
Useful points so let’s build on them.
i) The above statement is true only for the period up to 1995 – 2000 during which the warmth peaked around the time of the 1997/8 El Nino.
ii) Low level clouds have been decreasing since the mid 90s so less insulation = faster energy loss upwards.
iIi) Medium clouds have been increasing since the mid 90s and high clouds have been increasing since the late 90’s = more reflection of incoming solar energy.
iv) That represents a clear shift in the balance between insulation by low clouds and reflection by high clouds in favour of falling system energy content
v) We must now be cooling and in support of that we see a cessation of ocean heat content build up with some evidence that it is actually declining, we have a cessation of earlier tropospheric warming and we have increasing global albedo.
At the same time as all that we saw falling solar activity levels and a record negative AO with more meridional jets at around the same time as a record solar minimum after years of positive AO and high levels of solar activity.
Looks pretty obvious to me.
@Leif
I read the referenced paper and at best one can say that there is conflicting data. 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.
What was not presented here is that the data upon which the cloudiness aspect is based is somewhat suspect: “It is noted again that the ISCCP lower-troposphere cloud data may not be sufficiently reliable to detect GCR–cloud correlations.” If the data is not reliable enough to detect the correlation, then it would be hard to argue persuasively that it is not there. The paper does not present data from other solar minima v.s. cloudiness at the proposed latitudes and altitudes. All things considered, the (again) contradictory published works on the changes in cloudiness from Forbush events supports both positions. I have seen at least one reference to significant cloud cover changes within hours of the Earth being hit by a CME. Perhaps that was spurious.
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?
It seems obvious that the GCR flux at different energy threshholds must be sorted out first before looking for correlations. The linked paper does not show this, in fact does not mention the 10 GeV energy threshhold at all. That is odd because though this quote is true, “The latter study in particular explains the extended deep QP between cycles 23 and 24 and the effect of the sun’s very weak polar magnetic field. This in turn explains the record-high GCR levels during the cycle 23–24 QP (see Phillips 2009)” 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.
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. My reading of what little came from CERN is that the effect was much stronger than expected in the ‘correct’ energy range.