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Archiving earlier versions of CRUTEM


CRUTEM is a dataset derived from air temperatures near to the land surface recorded at weather stations across all continents of Earth. It has been developed and maintained by the Climatic Research Unit since the early 1980s, with funding provided mostly by the US Department of Energy. The lead scientist for most of this work was Professor Phil Jones, though many colleagues have also contributed. In recent years, the Met Office Hadley Centre (MOHC) have also been involved, especially in the regular updating of the operational version of CRUTEM (current version CRUTEM4). CRUTEM has been combined with the MOHC's dataset of sea surface temperatures to provide a near-global dataset of temperatures across Earth's surface, called HadCRUT. For example, the current version HadCRUT4 combines CRUTEM4 and HadSST3. These datasets have been widely used for assessing the possibility of anthropogenic climate change.

The latest version of CRUTEM is available at the Climatic Research Unit and at the Met Office Hadley Centre. The ACRID project focussed on publishing CRUTEM3, including the workflow from station data to gridded and global datasets, according to the linked-data method.

As an additional outcome of the ACRID project, we have also been able to assemble an archive of some earlier versions of CRUTEM, as reported by Osborn and Jones (2014). If you find these earlier versions of CRUTEM useful, then please acknowledge this work by citing:

Reference: Osborn TJ and Jones PD (2014) The CRUTEM4 land-surface air temperature data set: construction, previous versions and dissemination via Google Earth. Earth System Science Data 6, 61-69. doi: 10.5194/essd-6-61-2014

Uniquely identifying CRUTEM versions

After each major version of CRUTEM has been adopted as the current operational version (e.g. CRUTEM3 was adopted in 2006), it is updated each month. Each update adds an extra month's data to the end of the series, but also includes any late reported data for previous months and even previous years. Occasionally, changes affecting earlier values have also been made to correct errors that have been identified or to improve the homogeneity of the series. Each month, therefore, a new version of CRUTEM is generated. Roughly once per year, more extensive revisions to the database are made, and sometimes modifications to the algorithms are also made.

For most purposes, it has been sufficient to identify the version of the dataset that has been used in a particular study by the major version number (e.g. CRUTEM3) together with the appropriate reference. In some cases, it might be valuable to be able to identify a specific monthly update of the dataset; for instance, if it is necessary to identify the precise version used so that a particular published analysis can be repeated exactly.

Until recently, individual monthly updates of CRUTEM have not been uniquely identified. MOHC introduced a version numbering system when CRUTEM4 was released, which is updated when significant modifications to the data and/or algorithm are made. This can be combined with the labelling used in this archive, where we recommend that every monthly update can be uniquely labelled using an identifier that combines the major 'version' with the date corresponding to the latest data contained in the data file. Hence, a file containing data that run through to include values to the end of May 2011 would be labelled CRUTEM3-2011-05. Note that this is not the version that was created in May 2011 because that will likely have data that run through to only the end of April 2011 (and would be identified as CRUTEM3-2011-04). Updated versions are usually created 3 to 4 weeks after the end of the month.

An archive of CRUTEM versions

The earlier versions of CRUTEM (gridded and global/hemispheric means) that are currently available are linked to in the table below. These versions have been obtained from a number of sources, whose support is acknowledged, especially the Internet Archive's Wayback Machine.

Caveats. We cannot guarantee that the assignments of particular files to particular monthly versions is completely accurate. These have been recovered and/or recreated from various archives and because unique identifiers had never been attached to each monthly update, there is some uncertainty in assigning these files to particular monthly versions. If you identify errors or have additional or different older versions of a CRUTEM dataset, then you are welcome to contact Tim Osborn.

The formats of these datafiles have varied over time. Please refer to the CRU and MOHC websites for details of some of the formats that have been used.


Reference: Jones PD, Lister DH, Osborn TJ, Harpham C, Salmon M and Morice CP (2012) Hemispheric and large-scale land surface air temperature variations: an extensive revision and an update to 2010. Journal of Geophysical Research 117, D05127. doi: 10.1029/2011JD017139


Reference: Brohan P, Kennedy JJ, Harris I, Tett SFB and Jones PD (2006) Uncertainty estimates in regional and global observed temperature changes: a new dataset from 1850. Journal of Geophysical Research 111, D12106. doi: 10.1029/2005JD006548


Reference: Jones PD and Moberg A (2003) Hemispheric and large-scale surface air temperature variations: an extensive revision and an update to 2001. Journal of Climate 16, 206-223.


Note that the dataset was not called this at the time, but it has been retrospectively named as CRUTEM1.
Reference: Jones PD (1994) Hemispheric surface air temperature variations: a reanalysis and an update to 1993. Journal of Climate 7, 1794-1802.


These CRUTEM datasets are made available under the Open Database License. Any rights in individual contents of the database are licensed under the Database Contents License.