It turns out that the two records show insignificant coherence at frequencies below the Wolfe sunspot cycle (~11yrs). At these low frequencies, Cedarville is significantly coherent with Redding CA, while Golconda is similarly related to Mina and Lovelock NV. Thus Golconda provides no credible basis for any trend-altering “correction” of the Cedarville record.

In areas with steep climatic gradients, the longest rural record within a certain radius of the station to be “homogenized” does not necessarily provide an unbiased backbone for any adjustment. This ad hoc criterion is simply a device of computational convenience, rather than of climatological reasoning.

If the eol and/or eof character changes, or any other ‘editor artifact’ is left, then your dataset has been compromised.

If the MD5 sums don’t match, you can’t trust the data. Period.

Simmer them in beer (and onions), then grill them.

The only thing that can cause the MD5 hash to vary between machines is that the data being hashed (the gzip’ed tarball) has changed. The purpose of the MD5 (Message Digest Algorithm #5) is to ‘digest’ a document (text/binary doesn’t matter) into a small cryptographically secure (i.e. the chances of similar data producing the same MD5 hash is quite small) hashes that can be used to detect changes (from single-bit to blocks of data) in a dataset.

Of course, if the implementation of the algorithm to produce the hash is flawed (not necessarily unlikely with Microsoft software), then it could vary from what a linux MD5 (md5sum) algorithm produces, but microsoft would be forced to fix that immediately as the security community would go nuts.

That said, the literature does show methods that can be used to ‘craft’ a false text that will produce the same MD5 sum, which has caused cryptographers to use other digest algorithms (e.g. SHA-256).

1. Does homogenization improve the accuracy of the record? Me thinks not.

2. Does it adequately rein in the suspected “Batman” flaw? Possibly.

3. Does it introduce a positive recent trend into the data, where there was none before? Certainly!

From the perspective of an analysis of yearly deviations from the 20-th century means of vetted, intact records in this climate area, the “Batman” feature appears to be no flaw. The average result shows very stable temps, with 1926, 1934, and 1931 by far the warmest years of the century, with deviations well in excess of 2 sigmas. I see nothing in the Cedarville record to impeach it.

The remarkable thing about the GISS sausage machine, where anomalies are computed from homogenized data, is that the 1951-1980 “norm” is also changed thereby. Thus not only a false trend, but also a bias go into the computational legendermain. Moreover, from a climatic perspective, the use of stations from a wholly different climate area (e.g. Mina NV) just because they happen to fall within a ceratin distance is indefensible. As the widely divergent trends at neighboring stations clearly show, this topographically convoluted area is a quiltwork of microclimates.

But none of this seems to matter to the crew of spaceship GISS, who find the their sausage to be very tasty.

I did ask a few people, but was sidetracked by the fact that Christmas Island weather records are under “Christmas Island Aero”, when the earlier records are labelled under “Rocky Point”. This is confusing since there are many places called “Rocky Point” in Australia. When you check Christmas Island climate averages on http://www.bom.gov.au/climate/averages/ it is shown as “nearest alternative site” 4km away and that can be checked on any Christmas Island map.

Temperature data for Rocky Point is only shown for 1959-1972 whilst rainfall is from 1901 to 1973.
That doesn’t mean temperature data doesn’t exist. It may not have been entered in the data base. That means going to the archives to search the records. Checking the Australian National Archives web page shows they hold “Christmas Island weather observations books” for 1964-1966. That is not the end of it either, for Christmas Island is considered to be under the Bureau of Meteorology’s Western Australian Regional Office reponsibility and some of their data is also stored in the Western Australian State Archives.

I presume your interest doen’t go further, so I will give the archives a miss.

To solve other deletion problems, ask a local.

But what I’ve learned from thousands of solitary hours in the lab is that it is the anomaly that is most interesting. You should always watch out for anomalies. And try to see if they’re repeatable, and then find an explanation. More often than not, you will have found something new and unexpected.

Thank you for re-emphasising this point, with which I thoroughly agree.

Re # 45 Len van Burgel Christmas Island.

Thank you for this simple explanation. Do you know why 50 or so years of potentially good data were taken out? Did you find this explanation in a place where other deletion puzzles could be solved?

Likewise Christmas Island, deleted 1908-1970. This was mined for phosphate far some decades and so there were technical people there. One can only guess at the reason for deletion over these years.

Christmas Island (Indian Ocean) is the rocky outcrop of a submarine mountain. Its elevation extends up to 361m.
Prior to 1973, the observations are from Rocky Point (elevation 17m), near the settlement, right on the coast. From 1973 the observations are taken at a location 4km south at the airport (elevation 261 mtr). Understandably the mean annual maximum temperature is about 3C lower at the new site. Although the two locations are only 4km apart, it would be almost impossible to merge them in to a continuous record.