Met Office Hadley Centre and Climatic Research Unit HadCRUT4 and CRUTEM4 Temperature Data Sets Adjusted/Corrected/Updated… Can You Guess The Impact?

Image Credit: Met Office Hadley Centre

By Just The Facts, Werner Brozek and Walter Dnes

The Met Office Hadley Centre and the Climatic Research Unit at the University of East Anglia, have adjusted/corrected/updated their HadCRUT4 & CRUTEM4 data sets, the update occurred with the April data recently released. There does not appear to have been a press release and there was no mention of the forthcoming change in this April 15, 2013 Met Office press release that covers the data sets, however version update tags were placed in bold at the top of the HadCRUT4 page;

“Update: An updated version of HadCRUT4 is now available. HadCRUT4 is now at version HadCRUT.4.2.0.0. Details of this update can be found here

and the CRUTEM4 page:

Update: CRUTEM4 has been updated to version CRUTEM.4.2.0.0. Details of this update can be found here.

The HadCRUT4 page notes that the HadCRUT4 “land ensemble has been updated to use station data for CRUTEM4 version CRUTEM.4.2.0.0” and the Release Notes for version CRUTEM.4.2.0.0 state that:

“Additions to the CRUTEM4 archive in version CRUTEM.4.2.0.0

The changes listed below refer mainly to additions of mostly national collections of digitized and/or homogenized monthly station series. Several national meteorological agencies now produce/maintain significant subsets of climate series that are homogenized for the purposes of climate studies. In addition, data-rescue types of activities continue and this frequently involves the digitization of paper records which then become publicly available.

The principal subsets of station series processed and merged with CRUTEM (chronological order) are:

Norwegian – homogenized series

Australian (ACORN) – homogenized subset

Brazilian – non-homogenized

Australian remote islands – homogenized

Antarctic (greater) – some QC and infilling

St. Helena – some homogenization adjustment

Bolivian subset – non-homogenized

Southeast Asian Climate Assessment (SACA) – infilling /some new additions

German/Polish – a number of German and a few Polish series – non-homogenized

Ugandan – non-homogenized

USA (USHCNv2.5) – homogenized

Canada – homogenized

In addition, there have been some corrections of errors. These are mostly of a random nature and the corrections have generally been done by manual edits. For a listing of new source codes in use, see below (end).”

While the magnitude of the changes is not that large, many of the adjustments/corrections/updates to HadCRUT4;

and CRUTEM4;

are concentrated in the last 16 years, a period that the Met Office is under scrutiny for the lack of warming in their data.

Also, some of the regional changes appear quite contrived, e.g. it looks like they found five hundredths of a degree of extra warming in the Northern Hemisphere in the last couple years:

South America they found almost a tenth of a degree of warming over the last decade;

Africa, had five hundredths of a degree of extra warming in the last few years;

and Australia/New Zealand a tenth of a degree of additional warming over the last few years:

Now updating data sets to include additional measurement locations and improve precision is usually a good thing, and if this was the only occurrence of an adjustment/correction/update resulting in additional warming, one might give the Met Office Hadley Centre and the Climatic Research Unit at the University of East Anglia the benefit of the doubt. However, over the last several years they have progressed through;

CRUTEM.4.2.0.0 (current version)

CRUTEM.4.1.1.0 (previous version)

CRUTEM.4.0.0.0 (initial release)

CRUTEM.3 (Corrections)

and

HadCRUT.4.2.0.0 (current version)

HadCRUT.4.1.1.0 (previous version)

HadCRUT.4.0.0.0 (initial release)

HadCRUT.3 (Corrections)

and it seems like the impact of each adjustment/correction/update is to increase the appearance of recent warming. The move from HadCRUT3 to HadCRUT4 was particularly troubling, i.e.;

“HadCRUT4 was introduced in March 2012. [2]It “includes the addition of newly digitised measurement data, both over land and sea, new sea-surface temperature bias adjustments and a more comprehensive error model for describing uncertainties in sea-surface temperature measurements”. [3] Overall, the net effect of HadCRUT4 versus HadCRUT3 is an increase in the average temperature anomaly, especially around 1950 and 1855, and less significantly around 1925 and 2005. [4]Also, the warmest year on record, which was 1998 with HadCRUT3, is now 2010 with HadCRUT4. [5]” Wikipedia

The difference between HadCRUT3 to HadCRUT4 is clearly visible in this WoodForTrees graph;

however, note that WoodForTrees.org is still on CRUTEM.4.1.0.0, i.e. thus that difference will grow if/when WFTs is updated to CRUTEM.4.2.0.0

Also a note should be made regarding the graph that showed Hadcrut4 was about to go below the 95% mark. With the old version, 2011 and 2012 had anomalies of 0.399 and 0.433 respectively. The new Hadcrut4 has 2011 and 2012 go up to 0.406 and 0.448 respectively. It appears as if they bought themselves some time, but as you can see in the table, the average for the first three months is 0.420. So while this is even below the original 0.433, it is only for three months so it does not mean too much yet.

Alright, so how many of you guessed wrong and thought that the impact of the adjustments/corrections/updates to HadCRUT4 and CRUTEM4 was to decrease recent warming?…