New HADCRUT Version 4.2.0
May 10, 2013
By Paul Homewood
h/t Green Sand
The Hadley Centre have issued a new update to their HADCRUT4 series, Version 4.2.0.0
The changes from the previous Version 4.1.1.0 are only small, but nevertheless increase the warming trend, as my chart shows.
The changes all arise from modifications to the CRUTEM4 land series, so obviously the differences are much greater on this set, as the chart below shows.
The full reference notes are here.
http://www.metoffice.gov.uk/hadobs/crutem4/data/CRUTEM.4.2.0.0_release_notes.html
http://www.metoffice.gov.uk/hadobs/hadcrut4/data/versions/HadCRUT.4.2.0.0_release_notes.html
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NOT A LOT OF PEOPLE KNOW THAT 
The changes to annual HadCRUT4 anomalies may be relatively small, but there are some surprising changes to some individual months.
For example, the global anomaly for January 2013 appears to have been reduced from 0.432c to 0.378c and that for February 2012 has been increased from 0.208c to 0.277c.
In the case of the January 2013 change, the global anomaly is now lower than that for March 2013, despite the fact that the corresponding Crutem4 and HadSST3 anomalies are higher for January than March.
January 2013 is also much lower than that for April 2012, despite the fact that the Crutem4 and HadSST3 anomalies for that month were similar.
@QV
“The changes to annual HadCRUT4 anomalies may be relatively small”
But yet again a revision results in the past getting cooler and the present warmer?
If we really don’t know what the temperature was when our predecessors recorded it how can we possibly be certain that it needs to be revised?
There are no fixed numbers in climatology. All the surface temperature records are model outputs that they hope will somewhat resemble something people will believe as being temperatures. The Assumptions and Al-Gore-rhythms for the models will increase the present temperatures and decrease the past to justify the groups existence.
GISS says it best in this Q&A
http://data.giss.nasa.gov/gistemp/abs_temp.html
This can only be done with the help of computer models, the same models that are used to create the daily weather forecasts. We may start out the model with the few observed data that are available and fill in the rest with guesses (also called extrapolations) and then let the model run long enough so that the initial guesses no longer matter, but not too long in order to avoid that the inaccuracies of the model become relevant. This may be done starting from conditions from many years, so that the average (called a ‘climatology’) hopefully represents a typical map for the particular month or day of the year.
and
Q. What do I do if I need absolute SATs, not anomalies ?
A. In 99.9% of the cases you’ll find that anomalies are exactly what you need, not absolute temperatures. In the remaining cases, you have to pick one of the available climatologies and add the anomalies (with respect to the proper base period) to it. For the global mean, the most trusted models produce a value of roughly 14°C, i.e. 57.2°F, but it may easily be anywhere between 56 and 58°F and regionally, let alone locally, the situation is even worse.