Tuesday, October 13, 2009

Analysis of Australian Temperature - Part 5 - Cloud cover over time

What effect does cloud cover have on Australian temperatures? Has cloud cover increased or decreased over time? Obviosuly, and especailly during the day, the more clouds that abound, the lower the temperature, and conversely the less clouds during the middle of the day, the higher the temperature.

When the sun is set, the relationship is a little more dubius. Cloud free summer days will have hotter nights if there is cloud cover, however the more days that are cloud free, the higher the atmosphere will be to start off with.

Either way, have Australia’s cloud cover increased or decreased over time? Fortunately, the Australian Bureau of statistics provides good data on this, and we are even able to measure the level of cloud cover as a variable over certain times of the day.

The following are Australia’s cloud cover anomalies from 1950 until current. Note that from about 1996 to current for midnight, and from 2000 to current for 3am, limited data was available.

SO what does this show? Well quite clearly it shows no major change in cloud cover at midnight, but from then on the level of cloud cover decreases dramatically overtime, reaching its decreasing trend peak at 3pm, and then the trend increases, where it actually has a positive value at 9pm, before stabilising.

Take a special look at the last five years of cloud cover from 9am to 6pm. These are dramatic negative cloud cover anomalies, and if you remember what the temperatures looked like during these last few years at the same times, perhaps there is a strong relationship between the two.

It is interesting, that during the heat of the day at 3pm, the cloud cover trend is at its decreasing peak. This is interesting. Scientists do not know much about cloud cover and the reason why its levels vary. However quite clearly here, a pattern arises where the level of cloud cover has decreased over time up until 3pm, before increasing back to a level state. This is highlighted by the graph below.

What happens to Australia’s temperature over time, when we account for the changing values of cloud cover? We will find out in the next article.


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Anonymous said...

Interesting article you got here. I'd like to read a bit more about this theme.
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Ayrdale said...

I am looking forward to your analysis of the CRU (leaked) material.

Jonathan Lowe said...

i haven't done any, and dont really plan on doing it. Save that for climate audit and whats up with that.

From what I can read, there doesn't seem to be much dodgy stuff at all about it. The main issue that I can see is that the talk is very scientific. Our side vs your side, which is not what science is about.

Roger said...

Are you talking about the current (Dec 09) CRU emails?

You don't think the following looks a bit dodgy?! (From NYT piece on ICECAP)

a computer programmer writes of the CRU’s temperature database: “I am very sorry to report that the rest of the databases seems to be in nearly as poor a state as Australia was. . . . Aarrggghhh! There truly is no end in sight. . . . We can have a proper result, but only by including a load of garbage!”

Jonathan Lowe said...

goes to show that I properly haven't gone through them. What I was saying is that I dont see any doctoring of data, however what clearly shows is a major problem with the peer review status of science.

Roger said...

Jonnathan you don't see any doctoring of data! Try this (Herald Sun 24 Nov.)

FIDDLING DATA: "Hide the decline"

Phil Jones tells Mike Mann and others how he made his data show warming:

I've just completed Mike's Nature trick of adding in the real temps to each series for the last 20 years (ie from 1981 onwards) and from 1961 for Keith's to hide the decline.

Mick Kelly, Professor of Climate Change at Jones' university, on hiding recent cooling:

Anyway, I'll maybe cut the last few points off the filtered curve before I give the talk again as that's trending down as a result of the end effects and the recent cold-ish years.

A CRU programming code for dealing with tree-ring data:

Uses corrected MXD but shouldn't usually plot past 1960 because these will be artificially adjusted to look closer to the real temperatures.

From green entrepreneur Adam Markham to the CRU, asking for better propaganda:

(WWW Australia) are worried that this may present a slightly more conservative approach to the risks than they are hearing from CSIRO. In particular, they would like to see the section on variability and extreme events beefed up if possible.

Jonathan Lowe said...

the "hide the decline" is an interesting one. He is talking about huding the decline of lack of tree ring data (not temperature as many people believe). Phil Jones has stepped down while this is investigated.

The "trick" is another word for "clever thing to do" in science. If you look athte moving average trick, you will see that no data was fiddled, just that the model used to show the increasing temperature was not following the actual temperature. Hence the trick was actually a good piece of modelling that better represented the data. It was not fiddling data at all.

Roger said...

"(hiding) the decline of lack of tree ring data"?? I think you must be going over to the darkside..:)

Have you seen

which also makes the point about temps not declinimng. But if we don't know why "the model used to show the increasing temperature was not following the actual temperature" the model is not calibrated .. is not actually a model which of course must replicate the prototype. Why didn't they agree? Could it be because the UHI effect wasn't an issue 500 years ago?
Why the astonishingly good agreement between the 3 reconstructions between 1900-1950, the only time they get so close? If it looks too good to be true it probaly is.

On the other hand if you look at the graph of red-blue-green reconstructions (sorry it's not numbered) in the above article,an alternative "trick" would be to reconcile the reconstructions to the recent thermometer record by "sliding them up" so the 1990ish temps coincide. Within the accuracy/variability between the reonstructions, you still get agreement with actual record, but of course the illusion of higher than historic temps disapears.

Also check


Unfortunately again no para Nos. but the secion headed "A Clear and Present Rearranger" seems to me show data fiddling.

Jonathan Lowe said...

And also check out this write up too: Climate Audit

There's no light and dark side in science. Nor should there be. It is not like politics where you agree with everything that your party suggests and against anything that your opponant suggests.

I think that in 10 years time, if these two small things are the only dodgy cases, well, there is no case.

There seems to be no deliberate manipulation of data, at least, according to the emails.

What is concerning however, is how the scientific nature of peer review has got so political. This is one thing that is a major major concern as outlined in the emails, but not data manipulation.

Anonymous said...

Some very interesting material. Why not get Anthony Watts to put up your analyses on his wattsupwiththat.com site for some comment by experts ?

Dr A Burns said...

The real "hide the decline" happened after Briffa's 1998 paper.

Have a look at fig 6 which shows cooling since 1940 !

No wonder Briffa and his CRU mates wanted to hide this embarassment.

Any apparent warming in hadcrut is due to UHI and poor weather station location.

Jonathan Lowe said...

thanks, I was going to get in contact with anthony when I finish the analysis, still some more to come

Roger said...

Of course it's not so much the emails themselves ....


Anonymous said...

Henrik Svensmark predicted an 11 cycle of cloudiness based on the ionization of atmospheric particles (creating new nucleation targets) based on solar cycle variability of cosmic ray flux. I was wondering, do you see this cycle in your data? Can you Fourier Transform it?

Jonathan Lowe said...

take a look at the graphs and see what you think. There might be a cyclic pattern there, but I dont think it is well defined.

Cloud cover levels are decreasing, moreso during the day, and that is well defined.

Phil said...

Your blog has gone quiet, jonathan.

Anyway a physical mechanism for what you have discovered.

Reduced particulate pollution (smoke) particularly in the morning reduces cloud nucleating particles and hence clouds.

This in turn leaves more water vapour in the atmosphere to form clouds by after dusk cooling. Hence the 9pm trend.

Note this is the same physical mechanism that I proposed for the divergence between the fixed time temperature trend and Tmin.

Jonathan Lowe said...

indeed Phil, I'm a very busy man at the moment! I hope to update all my stats including the final couple of articles in the series.

Your comment is very interesting, would you be kind enough to forward me soe links or extra info on the area?

Technical translation services said...

Have somebody compared the Australian situation with for example the one in Europe. Can we see differences in development?