Adjustments to GISS, pre-Y2K, post-Y2k and current

[IanC]

from 19 Versions and Whadda You Get Climate Audit

Pre-Y2K: As of mid-2007, prior to the identification of the Y2K error, NASA used the vintage (2000) CDIAC SHAP version up to 2000 and the GHCN Raw version for 2000 and after. They removed any USHCN interpolations (made during the SHAP adjustment, which is included in the Filnet version BTW); instead of using the SHAP/Filnet interpolation, they used the Hansenizing interpolation that we’ve discussed elsewhere in connection with dset=1. [raise eyebrow /raise eyebrows]. The splice was particularly problematic if there was a TOBS or other adjustment in effect as at 2000 and this led to the Y2K error (and resulting bias). This process yielded the GISS “Raw” version (dset0). For USHCN stations, dset1 is equal to dset0 since there is only one record and the Hansenizing dset1 splice does not come into play. From this, they then did another adjustment – their two-legged trend adjustment to coerce results to unlit stations. What’s a little hard to understand about this methodology is why “lit” stations are being used at all, if the unlit stations are driving matters – but that’s a question for another day.

Post Y2K: After the Y2K problem was brought to their attention, they appear to have patched the above method by calculating (separately for each month) the difference between the GHCN Raw and Shap versions for the 15 years up to and including 1999 and then adjusting all data up to and including 1999 by this amount, in effect re-writing their entire USHCN data set to cope with the Y2K splicing error. I think that it would have made more sense to leave the 99% of the data in place and adjust the post-2000 data. The NASA two-legged adjustment was re-applied to the revised data, leading to revised adjustments.

Current: After these first changes were made in mid-August 2007, NASA scrubbed the modified version and issued an entirely new version, to our considerable consternation last September. It got a little hard trying to keep up, but things seem to have settled down. In their third go at this, they’ve used the CDIAC Filnet version up to December 2005, which is now combined with the GHCN Raw version (for the three further months up to March 2006). As in the first patch, they appear to have patched the discontinuity by calculating the 15 year difference by month and then applying this difference to all records prior to Dec 2005.

edthecynic and others proclaim that the gang from NASA are the ultimate authority on land temps. they post up links that say they are the ultimate authority and that they never make changes unless it is necessary but never give any actual figures. The grunt work is left to enthusiastic amateurs like McKitrick, McIntyre, Watts et al.

The link shows that these adjustments go back a hundred years and they are arbitrary. They do what they want. And the adjustments almost always decrease old temperatures and increase newer temperatures, greatly changing the temperature trend. Why? How can people work with figures that change several times a year?

On average 20% of the historical record was modified 16 times in the last 2 1/2 years. The largest single jump was 0.27 C. This occurred between the Oct 13, 2006 and Jan 15, 2007 records when Aug 2006 changed from an anomoly of +0.43C to +0.70C, a change of nearly 68%.

Wow.

The next question I had was “how often are the months within specific years modified?” As can be seen in the next chart, a surprising number of the earliest monthly averages are modified time and again.

I was surprised at how much of the pre-Y2K temperature record changed! My personal favorite change was between the August 16, 2007 file and the March 29, 2008 file. Suddenly, in the later file, the J-D annual temperature for 1880 could now be calculated. In all previous versions the temperature could not be determined.

from Rewriting History, Time and Time Again Climate Audit

When is the US Govt going to put in a forensics audit team to go in, write some real code, investigate the data, and give climate science a real and unchanging historic data set to work with? I am pretty sure there are a lot of top notch accounting firms that could do a better job and for a lot less money than Hansen and his cronies.

 

[westwall]

So true. However so long as the current political climate exists and we have people like Holdren in power it will never happen.