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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It would also be interesting to see how cloudiness has changed by latitudinal band eg tropic, temperate etc. and timing through the day. Willis might find support for his thermostat hypothesis, or not.
We have had more rain in Australia and flooding in 2010, 2011 and still some now. Particularly in winter that generally is are driest period. But what he says rings true. If solar activity slows, more galactic rays get through, however, they are only one part of the equation, ocean currents and volcanoes, can change the temperature also. The hotter is becomes, the more evaporation, more clouds. Move 50 miles away from the sea and precipitation levels drop naturally. Look at Australia and our shape. And of course in the USA you have deserts right in the middle of your continent, yet people have lived there at one time. I don’t know what all these climate change alarmists have been going on about all these years, but to scare the uneducated and poor in the world, that western richer countries are causing economic and agricultural downfalls and should pay for their faulty handling of their natural and human environment.
A suggestion….’over the past 39 years from 0.9 to 2.8% ‘ reads better as
‘over the past 39 years from between 0.9 to 2.8%’
Cumulonimbus are more common in warmer weather. Wouldn’t a temperature increase be expected to cause them to increase ?
Other cloud types are more likely to be effected by the Svensmark effect.
Cloud, rain, humidiry all tie in together in complex ways. Here are some more interesting figures from the settled science:
http://www.cgd.ucar.edu/cas/adai/papers/Dai_JC06-sfcHumidity.pdf
Maybe you want to fix
“Insolation” comes from the sun (our sun). Cosmic rays come from (notionally) exploded suns.
Perhaps change it to
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.
“that is, we don’t yet have the information to say that cloud cover changes (of whatever origin) cause temperature changes.”
Have you ever been outside on a sunny day, then had clouds cover the sun? What happens?
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.
That is what is being stressed at the outset of a CERN lecture on their cloud chamber experiments as well (Iposted the link so many times that I now grew tired pulling it up yet again). If clouds have a substantial effect either way, then of course even slight changes cannot be neglected or ignored, and knowing about them is crucial in determining their effect. In a related talk, they also say that as physicists, they have grave concerns with what boldness and conviction climate scientists throw their assertions around, where a physicist can only wonder what they are rooted in… and they bemoan the fact that research related to the cloud experiment has been rejected by one emminent science journal, in their view solely based on agenda…. there you go. It will be the physicists after all who’ll save the world – maybe.
Leif Svalgaard says:
August 20, 2012 at 10:50 pm
Except that as solar activity has generally decreased [hence cosmic ray intensity increased], Svensmark’s hypothesis would predict an increase in cloud cover.
Is there necessarily such a linear, positively correlated relationship? It appears more likely to me that there would be a “sweet spot” where you would maximize the cloud cover for a given intensity, but it would fall off to either side. Sort of like ringing a bell – if you’re not hitting it at the fundamental resonant frequency, it won’t be nearly as loud.
Could it not be that, with increased rays, the clouds will rain out too frequently, and be unable to gain large mass before they are induced to rain out again, thus producing a negative correlation between cosmic ray intensity and cloud cover? Leo G @ur momisugly August 21, 2012 at 12:13 am mentions an increase in rainfall over the same period…?
As this is based on observations is there any Time of Observation adjustment that is, or should be made?
so what about global dimming? If it`s getting less cloudy, we should get more solar radiation- which is not the case.
Here’s a little thought.
If the concentration of one atmospheric constituent goes UP, the concentration of other constituents MUST come down (basic maths).
If that doesn’t make sense .. blame this rather nnice Chardonnay 🙂
In her 2005 paper, Pinker looked at sunlight at the surface and considered variations in cloud cover as an explanation:
http://www.sciencemag.org/content/308/5723/850.abstract
Of course Pinker’s paper was the one used by Monckton in his infamous debate with Lambert on his Australian tour, summarised here by Jo Nova:
http://joannenova.com.au/2010/02/lamberts-pinker-tape-ambush-pr-stunt/
The more sthings change the more they stay the same.
Clouds are formed from water vapour. That comes from surface evapouration caused by heat. The higher the heat the more evapouration and cloud especially Cb cloud, due to the energetic cells, forming especially in the tropics.
At least that is how I see it which does not quite fit with Dr Spencer.
This will keep the scientists engaged for a while but the politicians will dismiss it out of hand. Having come up with various schemes to tax carbon they’re not going to shut that gold mine down, especially as taxing cosmic rays and solar magnetic activity will entail sending the bill to God . . . and he ain’t payin’.
That first graph is useless and the exclusion of data suggests that the actual (non-excluded data) may not be representative of the conclusion.
North America – Canada – United States or America
=
Mexico + Cuba + Dominican Republic + Guatemala + Costa Rica + Panama + El Salvador + Honduras
AKA Latin America; an small area where almost all the land in less than 200 miles from an ocean, is all tropical and much if not most of the large area long duration cloudy periods are tropical storm related. In short the first graph smells of cherries.
John Marshall says:
Clouds are formed from water vapour. That comes from surface evapouration caused by heat. The higher the heat the more evapouration and cloud especially Cb cloud, due to the energetic cells, forming especially in the tropics.
============================================================
Yes, clouds are formed from water vapour but the water vapour needs something to
condense it into the water droplets making up the cloud. The amount of cloud is governed
by the availability of sufficient condensation nucleii. You can have lots of water vapour
but without the condensation nucleii, it doesn’t form cloud.
Cosmic rays bombarding the atmosphere create some of these nucleii.
Shaviv gives a short list of papers on the page “Cosmic Rays and Climate” at his blog
(www.sciencebits.com). You can also check the CLOUD experiment run at CERN recently
to see how it all works..
Hmmm. So what they are saying, is that to reduce Global Warming, we need more aircraft flying and creating contrails.
So what the Greens need to campaign for, is the ending of taxes on air travel, and a government subsidy of ticket prices. This is not only good for the environment, it is also good for people who want to travel.
Do you think Greenpeace will be campaigning for more air travel soon? Pigs may fly before more aircraft do….
“that is, we don’t yet have the information to say that cloud cover changes (of whatever origin) cause temperature changes.”
Clouds certainly do affect temperatures and the effect of increased clouds is cooler daily temperatures. The night time effect is affected by daytime clouds, but is generally warming.
One source of confusion is that in some places, like NW Europe, warmer air masses cause clouds. So people think clouds cause warmer temperatures.
Here is a paper by our friend Trenberth that covers the subject.
http://www.cgd.ucar.edu/cas/adai/papers/DTR-JC-99-Paper.pdf
Some places are getting more cloudy, other places are getting less cloudy. Some places are getting warmer, others are getting colder. It’s called weather.
Wake me up when EVERY AREA is doing the same thing at the same time.
ZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZZ
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?
The absolute humidity of the atmosphere has been dropping
see
Philip Bradley says:
August 20, 2012 at 11:27 pm
…..http://climate4you.com/images/CloudCoverAllLevel%20AndWaterColumnSince1983.gif
If the absolute humidity drops then two things happen
1. There is less water vapor to condense to form clouds, this would be most apparent in temperate latitudes rather than at the equator which is very humid and convective weather will still form clouds
2. The lower humidity leads to lower enthalpy of the atmosphere so less energy is needed to raise the atmospheric temperature. So the same amount of energy will result in higher atmospheric temperatures.
These two changes will lead to a whole slew of interacting effects some of which will feed back. There may be other effects such as cloud seeding by neutrons, but if the amount of water in the atmosphere available to form cloud is reduced that effect will be reduced. Slight changes in the energy distribution in the atmosphere will change the relative strengths of the convective Hadley and Ferrel cells altering the paths of the jet streams. As Stephen Wilde points out if the Rossby waves happen to interact with say the Himalayas or just run over the central plains there will be subtly or hugely different effects.
REPLY: I know you would like to dismiss Svensmark out of hand, and I should have been clearer. There are some indications in the paper that certain types of clouds have in fact been on the increase while others are on the decrease.
Svensmark has always been clear that he was talking about low-level clouds and those have decreased: http://climate4you.com/images/CloudCoverAllLevel%20AndWaterColumnSince1983.gif
Solar science is similar to watching a really, really slow NASCAR race. Each lap of the Sun is about 30 days, plus or minus depending where you may be on the surface. Pit stops are a decade apart. Harken back to the days of the Indy 500 and the turbine engines of Andy Granatelli in ’67 and ’68. James Garner (the actor who drove the things) told Johnny Carson they had very slow response time and were just plain dangerous. A 1, 2 or 3+ second delay from when you changed the throttle to when you the car responded. The Sun is a great deal like the Granatelli cars – there’s delays in response to changes. If one compares the cumulative volume effect of solar output for the last few pit stops, one might conclude ther is a cumulative effect as the solar wind volume would tend to increase – i.e., it’s sphere gets bigger. The solar wind has decreased but there’s still a lot of stuff the Sun produced in the last few years that we’ve yet to move away from since we’ve not left the old outputs behind. Think in terms of the old Chrsyler Fluid Drive which prevented stalling.
One hopes Leif is right. I’d really like to grow tomatoes for another couple of pit stops.