There’s an interesting, if long and complicated, article about the adjustments to the Sea Surface Temperature set done in the revision to HADsst3. The basic conclusion that there’s not a good reason for the assumptions about what kind of temperature measuring was done, and the adjustments are making the data worse (less accurate) not better.
HadSST3 contains a series of adjustments. With the exception of the war-time glitch, they are not obvious from study of the record. Their existence is based on speculation and hypothesis. Calculation of the biases involves inverting a significant portion of written record’s meta-data for the period of the principal adjustment and ignoring detailed studies on the proportion and timing of changes in data sampling methods as well a speculation as to the magnitude of the various effects.
The principal effect of these adjustments is to selectively remove the majority of the long term variation from the earlier 2/3 of the data record and to disrupt circa 10-11y patterns clearly visible in the data. These changes are fundamentally altering the character of the original data.
The strong similarity in form between the variations in the original ICOADS data and the corrections deemed necessary to correct sampling biases is remarkable. All the more so in view of the lack of documentary information on which to base the estimated magnitude and timing of the adjustments.
The analysis presented here indicates that, outside the immediate war-time period, these adjustments are distorting and degrading the data rather than improving it.
A number of different analyses suggest that a simple correction to the war-time period (as was used before the creation of the Hadley Centre) provides a more coherent and credible result.
Comparison to studies of non SST data suggest that much of the variation in ICOADS is quite possibly due to real climate signals, not instrument bias. These variations require proper investigation, not a priori removal from the climate record.
All I can say is “Ouch! That’s gotta hurt!” ;-)
One can only hope that someday a full understanding of the land temperature adjustments can similarly be made…