“The subjectivity inherently involved in the homogeneity process means that two different adjustment schemes will not necessarily result in the same homogeneity adjustments being calculated for individual records. ” Wow- and they call this ‘science’ !

“The updated dataset remains limited to the post-1910 period because before this time the use of Stevenson screens was not consistent across Australia (Nicholls et al. 1996). Reference series prior to 1910 are unreliable … at most, about 60 unevenly distributed stations have sufficient data back to 1900, and only about 37 stations back to 1890, suggesting that reliable all-Australian averages will remain restricted to the post-1910 period.”
So we don’t even have a century’s worth of reliable raw data for Australia! This is fascinating stuff exposing the myth that climatologolists can attune their global numbers to within 0.5C accuracy – its a joke! Would you be interested in assisting me in working this up into an article?

Has anyone thought to check into how the little Stevenson screens are held together..like are they glued or nailed or screwed? What kind of screws or nails or glue is used..Is the glue white or clear..water based..where are these materials made..nails from China..? Waaait a minute. Communist China? Ah ha!

And the material..is it wood..? What kind of wood..how dense? Like is it a hardwood like hickory or ash, or is it light like cedar or pine.? Is it imported from those socialists in Canada?
And how about those little thermometers in there…who makes them and how do we know that there’s enough mercury or alcohol in there and that it’s not kool aid..kool aid? There’s another thing and who calibrates them? And getting back to the paint..are they sprayed or brushed..brushing leaves more paint and a rougher surface..what effect would that have on the sunlight hitting the paint surface..? You people are like a bunch of old spinsters gossiping at a quilting bee.. By God there’s enough nefarious goings on connected to those Stevenson screens to keep you people mumbling and yabbering for years.

This phase includes an admission that sometimes measurement systems are changed (thus resulting in a long-term measurement error), but homogenization is based on a belief that the error can be removed by comparing multiple nearby sites and hoping they were not all changed at the same time. Thus, changes at any single site can be adjusted back to the common behaviour of nearby sites and so the error is adjusted out of the data.

You might think this sounds like getting something for nothing, actually it presumes that the climate signal has been many times oversampled and you are using the high frequency component of the signal to correlate the low frequency data (i.e. the climate data) and then pull it back out of the oversampling. The theory at least is sound, but the final outcome is a synthetic signal pieced together with chewing gum and string. No way do after-the-fact adjustments make an equivalent substitute for good quality field measurements, but I think we must give the homogenization process reasonable due consideration.

There are a number of practical difficulties. Most obviously, sometimes many things change at approximately the same time. For example, the extensive changes around World War Two. You can’t use correlation to remove your error when the error exists simultaneously in all your measurements.

In other cases it is a bit of an individual judgement which way the adjustment should apply, this is fraught with the problem of unrepeatability and there are cases where these judgement calls were not properly documented so no one really knows why the adjustment was applied.

There’s a further problem with correlation between nearby stations when one station might be on the beach, another in the mountains, etc. Again, individual judgement is necessary to balance this, with results of somewhat questionable objectivity.

http://reg.bom.gov.au/amm/docs/2004/dellamarta.pdf

Above is one of the official explanations of how the homogenization process works — certainly not a simple process to explain. There’s an unofficial worked-example of how to detect the change in measurement equipment for Darwin that happened around 1940.

http://wattsupwiththat.com/2009/12/20/darwin-zero-before-and-after/

I’d be interested to know how many of your readers can get their heads around this process and decide whether it makes the errors smaller or larger.

It would be wonderful if those who have access to information regarding both the Stevenson screen types as well the automated electronic thermometers would put that into the public domain. For example, I’ve yet to see anything that proves modern automatic thermometers dovetail well with the performance characteristics of the older Stevenson models.

Also, there is no database that tells us how many Stevenson screens are still in use worldwide compared to automatic models, nor any humility from government climatologists willing to concede that any of the matters we’re touching on have been factored into their calculations. It strikes me that it ought to have been a crucial issue for manufacturers and world governments to resolve from the outset what standards of manufacture, testing and reliability were to be set in place for temp. measuring instruments. Without such safeguards then why should we believe them when they tell us they can measure the average global temperature within a fraction of one degree?

What we’ve identified that is consistent is the whole scale obfuscation and perversion of the scientific method by junk climatologists. Transparency of method just doesn’t exist – what we are presented with is voodoo smoke and mirrors trickery. None of these clowns is willing to fess up to the fact they failed to foresee how variables we’ve identified such as the exterior paint IR properties, the ventilation issue when manual screens are opened for access to read, etc. that all, in their own way, contaminate the data.

To be frank, if we were sat in court proceedings arguing over the evidential issues of this case I’d be asking the judge to rule that ground stations were inadmissible. The only reliable data, therefore, comes from oceanographic, radiosonde and satellite sources and I would gladly work from them. But sadly for the unscientific warmist lobby, those trustworthy data sources are proving fatal to their cause.

Also, how many sites still use the Stevenson screens? I thought most had been replaced by the automated thermometers.

It should be easily possible to figure out the effectiveness of these screens by building a bigger screen to put around the first screen. If the screen is effective then two screens would give identical temperature to one screen (presuming identical exterior conditions).

If the double-screen is different to the single screen then that gives you a good estimate of the error involved.