In a nutshell, with a −1.6%per decade change in cloud cover during 1954–2005, it becomes a climate forcing. While China is not the world, it bears consideration.
The Hockey Schtick reports:
New paper finds significant, natural decrease in cloudiness over past 50 years
A paper published last week finds that cloud cover over China significantly decreased during the period 1954-2005. This finding is in direct contradiction to the theory of man-made global warming which presumes that warming allegedly from CO2 ‘should’ cause an increase in water vapor and cloudiness. The authors also find the decrease in cloud cover was not related to man-made aerosols, and thus was likely a natural phenomenon, potentially a result of increased solar activity via the Svensmark theory or other mechanisms. As climatologist Dr. Roy Spencer has pointed out his book,
“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.”
Ann. Geophys., 30, 573-582, 2012
www.ann-geophys.net/30/573/2012/
doi:10.5194/angeo-30-573-2012
X. Xia
LAGEO, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China
================================================================
Abstract:
An updated analysis of cloud cover during 1954–2005 in China was performed using homogeneous cloud cover data from 314 stations. Long-term changes in frequencies of different cloud cover categories and their contributions to long-term changes in cloud cover were assessed. Furthermore, aerosol effects on cloud cover trends were discussed based on comparison of cloud cover trends in polluted and mildly polluted regions. Frequencies of clear sky (cloud cover <20%) and overcast days (cloud cover >80%) were observed to increase by ~2.2 days and decrease by ~3.3 days per decade, respectively, which accounts for ~80% of cloud cover reduction. Larger decreasing trends in cloud cover due to larger increase in clear sky frequency and larger decreases in overcast frequency were observed at stations with lower aerosol optical depth. There is no significant difference in trends regarding cloud cover, clear sky frequency, and overcast frequency between mountain and plain stations. These results are inconsistent with our expectation that larger decreasing trends in cloud cover should have been observed in regions with higher aerosol loading where more aerosols could lead to stronger obscuring effect on ground observation of cloud cover and stronger radiative effect as compared with the mildly polluted regions. Aerosol effect on decreasing cloud cover in China appear not to be supported by this analysis and therefore, further study on this issue is required.
Summary:
A homogeneous cloud cover dataset in China was used to study long-term changes in cloud cover and frequencies of cloud cover categories. A simple yet effective statistical method was applied to study quantitative contributions of graded cloud cover frequency to the overall trend in cloud cover. The relationship between AOD and cloud cover trend was analyzed to discuss aerosol effects on decadal trend of cloud cover. Major conclusions follow.
Significant decline in cloud cover with trend of −1.6%per decade during 1954–2005 was derived. Occurrences of clear sky (cloud cover <20 %) and overcast days (>80 %) were observed to increase and decline by 2.2 days per decade and 3.3 days per decade, respectively. Approximately 80% of overall trend of cloud cover is attributable to an increase in clear-sky days and a decline in overcast days.
Larger decreasing cloud-amount trends have been observed due to larger increasing clear sky frequency and larger decreasing overcast frequency at stations with lower AOD.
There is not significant difference among trends of cloud cover, clear sky frequency, and overcast sky frequency between mountain and plain stations. These analyses do not
support the speculation that the decreasing trend of cloud cover in regions with higher AOD should be larger than that in mildly polluted regions due to stronger aerosol obscuring effect on ground observation of cloud cover and stronger radiative effect in polluted regions. This suggests that causes for significant decreasing trend in cloud cover in China require further study.
Link to the full paper is here: http://www.ann-geophys.net/30/573/2012/angeo-30-573-2012.pdf
James Sexton, from that paper: Abstract
The relationship between summer temperature, total cloud cover and precipitation over
Eurasia was investigated using observation-based products of temperature and precipitation,
and satellite-derived cloud cover and radiation products. We used a partial least squares
regression approach to separate the local influences of cloud cover and precipitation on
temperature variations. Our results suggest that the variance of summer temperature is partly
explained by changes in summer cloudiness. The summer temperature dependence on cloud
cover is strong at the high latitudes and in the middle latitude semi-humid area, while the
dependence on precipitation is strong in the Central Asia arid area and the southern Asia
humid area. During the period 1982–2009, the damped warming in extended West Siberia
accompanied with increases in cloud cover, and the pronounced warming in Europe and
Mongolia was associated with a decrease in cloud cover and precipitation. Our results suggest
that cloud cover may be the important local factor influencing the summer temperature
variation in Eurasia while precipitation plays an important role at the middle latitudes.
Much more of this sort of analysis is needed.
To many:
http://www.leif.org/research/The%20long-term%20variation%20of%20solar%20activity.pdf slide 18 [the oval] shows solar activity. Slide 29 shows that PMOD was too low lately and that there is no difference between minima in TSI. The solar microwave flux shows the same: http://www.leif.org/research/Solar-Microwaves-at-23-24-Minimum.pdf . http://www.leif.org/research/Neutron-Monitors-Real-Time.htm [last slide] look at Hermanus [the red curve] shows that there has been no trend in cosmic rays.
@TomRude “… pressures have been steadily rising over the Gobi Desert in China since 1960 and temperatures have been decreasing there during the same period … shows the increase in Mobile Polar Highs reaching deeper southward, hardly a signature of global warming…”
Didn’t know this, thanks for sharing.
Richyroo asks: “If GCR do catalyse cloud seed formation a la Svensmark, wouldnt they subsequently fail to reach ground based measurement locations?
Put another way, if GCR’s are ‘used up’ making clouds, would that diminnish the signal recieved at ground measurement stations?”
No, they are not “used up.” The claim is that they leave an ionized trail of condensate.
Leif, IIRC, it was only one class of cosmic radiation that was supposed to promote cloud formation. Does the neutron monitor discriminate between different types of cosmic rays?
@angelpbj: Thanks.
A good reading that helps understand the various observations:
http://ddata.over-blog.com/xxxyyy/2/32/25/79/Leroux-Global-and-Planetary-Change-1993.pdf
Septic Matthew/Matthew R Marler says:
April 4, 2012 at 7:33 pm
James Sexton, from that paper: Abstract
……….. Our results suggest that cloud cover may be the important local factor influencing the summer temperature variation in Eurasia while precipitation plays an important role at the middle latitudes.
Much more of this sort of analysis is needed.
=============================================================
While there is some good information in the paper, I’m not sure we needed someone to tell us summer temps are effected by cloud cover. From their conclusions…… “new evidence of strong damping
effects of daytime cloud cover on summer temperature.”
And then there’s this revelation from the press release…..“What’s more, there is a strong correlation between precipitation and cloud cover …..” http://environmentalresearchweb.org/cws/article/news/49174
I suppose I should welcome their epiphanies, but it makes me want to cry at the same time. Further, when I look at this paper on clouds/temps, and look at the referred material, there is absent names I would expect on a paper about clouds. …….. “the damped warming….”…… it’s as if they wouldn’t or couldn’t say “cooling”. Again, there is some useful information in the paper, which is why I would try to direct Dr. Spencer’s attention to it………. in many ways it complements Anthony’s gem that he came across.
“This finding is in direct contradiction to the theory of man-made global warming which presumes that warming allegedly from CO2 ‘should’ cause an increase in water vapor and cloudiness. ”
Based on this ridiculous assertion alone one can only assume you didn’t bother reading the paper or perhaps you just decided to be a little bit deceitful and ignore the section that mentioned that while cloud cover decreased over China, cloud cover increased over, hang on, I’ll just cut and paste directly so there’s no mistake…”These studies have suggested total cloud cover has increased over Europe (Henderson-Sellers, 1986), Australia (Jones and Henderson-Sellers, 1992), Canada (Milewska, 2004), the United States (Sun and Groisman, 2004; Dai et al., 2006), the Former Soviet Union (Sun and Groisman, 2000), and the northern Indian Ocean (Norris, 2001).”
Hmmm, thats a fair chunk of the rest of the world.
Analysing the sensitivity of a simple two layers model (yea with two it’s enough to get a fair approximation) for three major parameters:
– For each % increase of albedo α, surface temperature will decrease by 1.0 °C.
– For each % increase of cloudiness c, surface temperature will increase by 0.5 °C.
– For each % increase of surface emissivity ε, surface temperature will decrease by 0.8 °C.
http://bit.ly/GGZ1r2
But the major challenge is to measure an average evolution of an average cloudiness over a long time line. Temperature is already difficult enough.
Interesting is also to observe how precipitations (cloud destruction) evolve in different parts of the World: http://bit.ly/HhPyOj
Last month’s flurry of the solar CMEs resulting in a 14% Forbush decrease, appears to confirm the Svensmark’s hypothesis, with a short term fall in the cloudiness approaching 7%.
http://www.vukcevic.talktalk.net/Ap-Cl.htm
@Leif
“Solar activity was largest in the middle of the 20th century and has since basically decreased to where it is now down to what it was at the beginning of the 20th century. In spite of this, the cosmic ray intensity has not shown any trend since reliable measurements began in the early 1950s, so it would seem hard to ascribe the decrease in cloud cover to any solar variable.”
++++++++
The demonstration of the CR effect is I think undisputed, right? No one is claiming anymore that the physics are not real.
So there remain some interesting possiblities. The cloud cover change is real and we and we have two postulates on offer: the GCM’s say the cloud cover should be increasing, it is decreasing, so they are in that single respect falsified.
The heliosphere is the diverter of GCR. You mentioned CR, not GCR. Solar CR and GCR are not the same thing. Can they be differentiated? My understanding is yes, definitely. So a simple question is whether or not there has been a fluctuation in the GCR with solar activity, and similarly has there been a fluctuation in Solar CR on the same basis.
Does the heliosphere size match the ‘solar activity’ and on what basis is this connect/disconnect made? In other words what constitutes ‘solar activity’. Basic queston I know, but just covering the bases.
It is going to be pretty tough for someone to prove that CR and GCR are not causing cloud formation as the evidence is pretty clear they do and the microphysics of cloud formation is pretty well understood. If CR and GCR hitting the Earth do not affect cloud cover and are not cyclic with solar activity, we must seek another explanation for long term changes in cloud cover.
Robert Brown says: “
To Leif:
IIRC, both the solar magnetic field and the Earth’s magnetic field fluctuate, and both affect cosmic ray counts. Polar stations e.g. Oulu do show significant increases in neutron counts since e.g. the early 80′s (~25%), do they not (which is more likely to be associated with solar fields). But as the Earth’s magnetic pole wanders and the Earth’s field fluctuates, might that not modulate cosmic ray counts as well, quite possibly in tropical regions with a differential impact on climate?
Robert – an interesting suggestion that fits with the comments and graphics of Vukcivic on this subject. These cover the fluctuating bands of plasma that follow the magnetic field lines where the magnetic and geographic equators cross – resulting from an interaction of the sub-tropical jets with the equatorial magnetic field. http://www.vukcevic.talktalk.net/LFC20.htm At places brighter spots of plasma are concentrated, most of which are associated with thunderstorms but their positions vary with GMF flux. As vukcevic states:
“As intensity of the GMF changes with time, so it will position of the magnetic Equator (and importantly) with it location of the plasma bands. One measure of this movement is the location of equatorial crossing. The equatorial crossing has moved east-wards during the last four centuries. “
My question is whether these differences in plasma concentration along the magnetic/geographic equator offer an explanation for the differences between the studies of Lindzen and Lin concerning the “iris effect” and could this be by variable modulation of cosmic rays by this plasma belt?
http://www-eaps.mit.edu/faculty/lindzen/236-Lindzen-Choi-2011.pdf
http://trmm.chpc.utah.edu/paper/liuietiali2008ijgr.pdf
Mike says:
Based on this ridiculous assertion alone one can only assume you didn’t bother reading the paper or perhaps you just decided to be a little bit deceitful and ignore the section that mentioned that while cloud cover decreased over China, cloud cover increased over, hang on, I’ll just cut and paste directly so there’s no mistake…”These studies have suggested total cloud cover has increased…
=============================
You just quoted what OTHER papers have previously asserted, not what this paper asserts. It’s remarkable that some posters can complain about misunderstandings when they have in fact managed to confuse themselves.
u.k.(us) says:
April 4, 2012 at 5:36 pm
” Don’t forget the early spring in the U.S. midwest; the trees, shrubs and plants are nearly in full bloom, one month early.
With all that shade, the ground warms slower.”
Sure, but where do you start? With all that shade the preceding winter, the ground cools slower too. The nights especially are much warmer under a cloud cover.
According to the book “Canicules et glacierese – Histoire humaine ed comparèe du climat” by the French historian Emmanuel LeRoy Ladurie, during the Maunder Minimum the astronomical observations where difficult because of a persistent cloud cover, with observatories forced to work only 1 night over 3…
James Sexton says:
April 4, 2012 at 11:13 pm
There is also a strong correlation between cloud cover and sun bathing!
Poleward shifting jets and climate zones give decreased cloudiness and more energy into the oceans to skew ENSO in favour of warming El Ninos.
The opposite for equatorward shifting jets and climate zones.
Previously discussed here:
http://climaterealists.com/index.php?id=6645
“How The Sun Could Control Earth’s Temperature”
meaning variations in such temperature for someone who was pernickety about the title.
peter azlac says:
April 5, 2012 at 1:28 am
………….
Thanks for highlighting my effots.
Geomagnetic equator’s position is determined by magnetic strength of two poles and their geographic location. The ‘south’ pole is relatively strait forward, its strength is falling off at a steady rate and its movement is simple.
Variability in the North hemisphere is more complex; there is a bifurcation of the field with the ‘apparent pole’ wandering around, as the balance between two extremities changes. There is strong possibility that this balance is altered by impact of the geomagnetic storms due to the solar coronal mass ejections – the CMEs and not related to GCRs. http://www.vukcevic.talktalk.net/Tromso.htm result: the ‘north’ magnetic field intensity correlates well with the long term changes in the solar activity.
‘Speculative’ info at: http://www.vukcevic.talktalk.net/MF.htm
Leif Svalgaard says: April 4, 2012 at 2:40 pm
“Solar activity was largest in the middle of the 20th century and has since basically decreased”
Being economical with the actualite again Leif? Tut tut.
After we knock off your 20% From the period in the mid C20th you say was overcounted, and allow for the short, steep ramped cycles following, it’s easy to see that solar activity was cumulatively increasing above the long term average since 1749 all the way from ~1934 to ~2003.
Why you would wish to mislead by omission of important facts I can’t imagine.
The standardized method of temperature measurement (Stevenson screen) is quite sensitive to ground radiation (as readers of this site would know). One therefore needs to ask the question; would the same temperature rise be evident if the measurements were taken higher above the ground? (ie 10 or 20m). I am not implying that there’s no connection between CC and LT temperature, merely pointing out the limitations of ground based measurements.
Could deforestation be one of the cloud cover variation mechanisms?
Could desiccation be another?
Here is a model based on IPCC assumptions that states that China should expect more floods.
And from the IPCC
Make of it what you will.
I think that this paper could possibly prove the ACRIM composite to be right, and the PMOD composite to be wrong.
This paper published in 2001 shows a significant link between direct solar variations and cloud cover changes.
http://www.agu.org/pubs/crossref/2001/2000GL012659.shtml
So if Cloud Cover is decreasing, and the trend is statistically significant, couldn’t this verify the ACRIM composite which shows a statistically significant trend upward between Solar Cycle minimas over the last 30 years?
This finding is in direct contradiction to the theory of man-made global warming which presumes that warming allegedly from CO2 ‘should’ cause an increase in water vapor and cloudiness.
Why? On the other hand, higher temperatures mean that you also need much more water vapour to form clouds.
Tom_R says:
April 4, 2012 at 9:47 pm
Leif, IIRC, it was only one class of cosmic radiation that was supposed to promote cloud formation. Does the neutron monitor discriminate between different types of cosmic rays?
No, but the Earth’s magnetic field does: The low energy GCRs that are not supposed to be active do not reach lower latitudes. The high-energy GCRs are much less modulated by solar activity.
Crispin in Johannesburg says:
April 5, 2012 at 12:58 am
The demonstration of the CR effect is I think undisputed, right? No one is claiming anymore that the physics are not real.
The efficiency of the process seems much too low to have any effect. More importantly, the claimed correlations do not hold up.
The heliosphere is the diverter of GCR. You mentioned CR, not GCR. Solar CR and GCR are not the same thing.
When speaking about cosmic rays one always mean the galactic ones. The solar ones are called Solar Energetic Particles and are of much lower energy and abundance [thus should have no climate effect].
Does the heliosphere size match the ‘solar activity’ and on what basis is this connect/disconnect made? In other words what constitutes ‘solar activity’.
Short answer is ‘yes’. Solar activity is the occurrence of magnetic fields and their various side effects.
It is going to be pretty tough for someone to prove that CR and GCR are not causing cloud formation as the evidence is pretty clear they do
That is wishful thinking. The evidence is too weak to be taken seriously.
peter azlac says:
April 5, 2012 at 1:28 am
But as the Earth’s magnetic pole wanders and the Earth’s field fluctuates, might that not modulate cosmic ray counts as well, quite possibly in tropical regions with a differential impact on climate?
Yes, and that modulation is much larger than the solar modulation.
As vukcevic states:
Most of what he says is pure nonsense. [and he is proud of it…]
tallbloke says:
April 5, 2012 at 2:41 am
it’s easy to see that solar activity was cumulatively increasing above the long term average since 1749 all the way from ~1934 to ~2003.
Slide 2 of http://www.leif.org/research/SHINE-2011-The-Forgotten-Sun.pdf shows solar activity since 1840 [sunspot number, geomagnetic activity, and the magnetic field in the Heliosphere]. As you can see, activity was low broadly around 1900 and 2010 and high in between. If the Sun modulates climate in any significant way, the climate now should resemble that of the early 1900s. Does it?
I’ve had a look at hours of sun records from two data sets, in Hungary (a continental climate) and the UK (a maritime climate) and solar exposure from Australia. In all cases the units they measure, hours of sun or solar exposure, are inversely related to cloudiness.
The Hugarian data show that average daily hours of sun increased 0.02 hours a day, relative an average of 5.3 hours, over the period 1970 to 2000. The Australian data show that solar exposure increased by 0.45 MJm-2year-1 relative to an average of 17.9 MJm-2. The UK data are most interesting. They show that in the period up 1966, when temperatures were falling, hours of sun fell 0.04 hours/year. In the period up to 2000, when temperatures were rising, they increased at the same rate.
The data are not strictly equivalent but all appear to confirm that there is a positive link between temperature and cloudiness. You can see the full analysis at:
http://www.climatedata.info/Discussions/Discussions/opinions.php
…under the heading ‘Trends in cloudiness and temperature’.