Climatic Research Unit : Data

CRU Data Availability 

The Climatic Research Unit (CRU) at the University of East Anglia (UEA) has, since 1982, made 

available gridded datasets of surface temperature data over land areas and averages for the Northern and 

Southern Hemispheres and the Globe. Until the development of the internet these were made available 

via various media. These datasets (the latest being CRUTEM3 

http://www.cru.uea.ac.uk/cru/data/temperature/) have been developed from data acquired from weather 

stations around the world. Almost all these weather stations are run by National Meteorological Services 

(NMSs) and they exchange these data over the CLIMAT network, which is part of the World 

Meteorological Organization's (WMO) Global Telecommunications System (GTS). Much of the original 

data in the early 1980s came from publications entitled 'World Weather Records'. We also make use of 

data available from the National Climatic Data Center in Asheville, North Carolina (their Global 

Historical Climatology Network, GHCN). We are also constantly striving to find additional, and 

homogenized data from a wide range of sources (see details of earlier work in the publications below). 

Both the gridded datasets and the station data archive have evolved over the years and we developed 

dataset version numbers in the early 1990s. The methodology we have used in developing the gridded 

datasets has been described in numerous publications in the climate literature (see list at the end of this 

document and also http://www.cru.uea.ac.uk/cru/data/temperature/ and the linked FAQs). 

Since the early 1980s, some NMSs, other organizations and individual scientists have given or sold us 

(see Hulme, 1994, for a summary of European data collection efforts) additional data for inclusion in the 

gridded datasets, often on the understanding that the data are only used for academic purposes with the 

full permission of the NMSs, organizations and scientists and the original station data are not passed 

onto third parties. Below we list the agreements that we still hold. We know that there were others, but 

cannot locate them, possibly as we've moved offices several times during the 1980s. Some date back at 

least 20 years. Additional agreements are unwritten and relate to partnerships we've made with scientists 

around the world and visitors to the CRU over this period. In some of the examples given, it can be 

clearly seen that our requests for data from NMSs have always stated that we would not make the data 

available to third parties. We included such statements as standard from the 1980s, as that is what many 

NMSs requested. The inability of some agencies to release climate data held is not uncommon in climate 

science. The Dutch Met Service (KNMI) run the European Climate Assessment and Dataset (ECA&D, 

http://eca.knmi.nl/) project. They are able to use much data in their numerous analyses, but they cannot 

make all the original daily station temperature and precipitation series available because of restrictions 

imposed by some of the data providers. A series of workshops (see Peterson and Manton, 2008 for 

details) has been held in diverse regions of the world to produce analyses of trends in extremes. NMSs 

are generally happy to release derived products from their data, even if they restrict access to their 

digital climate archives. A third example is the Global Precipitation Climatology Centre 

(http://gpcc.dwd.de), run by the German Weather Service (DWD) who make various versions of gridded 

precipitation datasets freely available, but due to restrictions imposed by data providers are not able to 

give access to any of the station monthly precipitation totals. The problem is a generic issue and arises 

from the need of many NMSs to be or aim to be cost neutral (i.e. sell the data to recoup the costs of 

making observations and preparing the data). 

We receive numerous requests for these station data (not just monthly temperature averages, but 

precipitation totals and pressure averages as well). Requests come from a variety of sources, often for an 

individual station or all the stations in a region or a country. Sometimes these come because the data 

cannot be obtained locally or the requester does not have the resources to pay for what some NMSs 

charge for the data. These data are not ours to provide without the full permission of the relevant NMSs, 

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organizations and scientists. We point enquirers to the GHCN web site. We hope in the future that we 

may be able to provide these data, jointly with the UK Met Office Hadley Centre, subject to obtaining 

consent for making them available from the rights holders. In developing gridded temperature datasets it 

is important to use as much station data as possible to fully characterise global- and regional-scale 

changes. Hence, restricting the grids to only including station data that can be freely exchanged would 

be detrimental to the gridded products in some parts of the world. 

We are not in a position to supply data for a particular country not covered by the example agreements 

referred to earlier, as we have never had sufficient resources to keep track of the exact source of each 

individual monthly value. Since the 1980s, we have merged the data we have received into existing 

series or begun new ones, so it is impossible to say if all stations within a particular country or if all of 

an individual record should be freely available. Data storage availability in the 1980s meant that we 

were not able to keep the multiple sources for some sites, only the station series after adjustment for 

homogeneity issues. We, therefore, do not hold the original raw data but only the value-added (i.e. 

quality controlled and homogenized) data. The priorities we use when merging data from the same 

station from different sources are discussed in some of the literature cited below. Parts of series may 

have come from restricted sources, whilst the rest came from other sources. Furthermore, as stated in 

http://www.cru.uea.ac.uk/cru/data/landstations/ we have never kept track of changes to country names, 

as it is only the location and the station's data that are important. So, extracting data for a single country 

isn't always a simple task. 

We rely on the CLIMAT network for updating CRU data series in near-real time. After quality control at 

the Hadley Centre these data are made available (since 2000) at 

http://hadobs.metoffice.com/crutem3/data/station_updates/. Much climate data are now additionally 

available through the internet from NMSs, but these are often difficult to use as data series often refer to 

national numbering systems, which must be related back to WMO Station Identifiers. Furthermore a 

number of NMSs make homogenized data (after adjustments for example for site moves, instrument 

improvements and changes in the way averages are calculated) available in delayed mode over the 

internet. Some that provide both raw and homogenized versions, generally do not link the two sets of 

data together. 

Some years ago, WMO enacted Resolution 40 (http://www.map.meteoswiss.ch/mapdoc/WMO/WMOresol40.htm) which covers the exchange of meteorological data and many data 

products and services produced by NMSs. This resolution applies only to NMSs and whilst Annex 1 

implies that much data should be freely available for research and operational uses (commercial is 

discussed separately in the resolution), many still impose conditions and charge for access (see the 

earlier discussion related to KNMI and GPCC). 

The HadCRUT3 product is a blend of land surface (CRUTEM3) and sea surface temperatures 

(HadSST2), CRU developing the land series and the Hadley Centre the SST series. Real-time updates of 

both components are performed at the Hadley Centre (data available at http://hadobs.metoffice.com/ and 

also on the CRU site). The collaboration has been ongoing for more than 20 years. A similar set of 

publications on the Hadley Centre site document the development of the SST datasets. 

Files 

 Data agreements 

References 

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 Hulme, M., 1994: The cost of climate data: A European experience. Weather 49, 168-176. 

 Peterson, T.C. and Manton, M.J., 2008: Monitoring changes in climate extremes: a tale of 

international collaboration. Bull. Amer. Meteorol. Soc. 89, 1266-1271. 

Literature describing the development of CRU land temperature 

datasets 

 Brohan, P., Kennedy, J., Harris, I., Tett, S.F.B. and Jones, P.D., 2006: Uncertainty estimates in 

regional and global observed temperature changes: a new dataset from 1850. J. Geophys. Res.

111, D12106, doi:10.1029/2005JD006548. 

 Jones, P.D. and Moberg, A., 2003: Hemispheric and large-scale surface air temperature variations: 

An extensive revision and an update to 2001. J. Climate 16, 206-223. 

 Jones, P.D., New, M., Parker, D.E., Martin, S. and Rigor, I.G., 1999: Surface air temperature and 

its variations over the last 150 years. Reviews of Geophysics 37, 173 199. 

 Jones, P.D., Wigley, T.M.L. and Kelly, P.M., 1982. Variations in surface air temperatures, Part 1: 

Northern Hemisphere, 1881-1980. Monthly Weather Review 110, 59-70. 

 Jones, P.D., Raper, S.C.B., Bradley, R.S., Diaz, H.F., Kelly, P.M. and Wigley, T.M.L., 1986: 

Northern Hemisphere surface air temperature variations: 1851-1984. Journal of Climate and 

Applied Meteorology 25, 161-179. 

 Jones, P.D., Raper, S.C.B. and Wigley, T.M.L., 1986: Southern Hemisphere surface air 

temperature variations: 1851-1984. Journal of Climate and Applied Meteorology 25, 1213 1230. 

 Jones, P.D., Wigley, T.M.L. and Wright, P.B., 1986: Global temperature variations, 1861-1984. 

Nature 322, 430-434. 

 Jones, P.D., 1988: Hemispheric surface air temperature variations: Recent trends and an update to 

1987. Journal of Climate 1, 654-660. 

 Jones, P.D., Groisman, P.Ya., Coughlan, M., Plummer, N., Wang, W-C. and Karl, T.R., 1990: 

Assessment of urbanization effects in time series of surface air temperature over land. Nature 347, 

169-172. 

 Jones, P.D. and Briffa, K.R., 1992: Global surface air temperature variations over the twentieth 

century: Part 1 Spatial, temporal and seasonal details. The Holocene 2, 165-179. 

 Jones, P.D., 1994: Hemispheric surface air temperature variations: a reanalysis and an update to 

1993. Journal of Climate 7, 1794 1802. 

 Bradley, R.S., Kelly, P.M., Jones, P.D., Goodess, C.M. and Diaz, H.F., 1985: A Climatic Data 

Bank for Northern Hemisphere Land Areas, 1851-1980, U.S. Dept. of Energy, Carbon Dioxide 

Research Division, Technical Report TRO17, 335 pp. 

 Jones, P.D., Raper, S.C.B., Santer, B.D., Cherry, B.S.G., Goodess, C.M., Kelly, P.M., Wigley, 

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T.M.L., Bradley, R.S. and Diaz, H.F., 1985: A Grid Point Surface Air Temperature Data Set for 

the Northern Hemisphere, U.S. Dept. of Energy, Carbon Dioxide Research Division, Technical 

Report TRO22, 251 pp. 

 Jones, P.D., Raper, S.C.B., Cherry, B.S.G., Goodess, C.M. and Wigley, T.M.L., 1986: A Grid 

Point Surface Air Temperature Data Set for the Southern Hemisphere, 1851-1984, U.S. Dept. of 

Energy, Carbon Dioxide Research Division, Technical Report TR027, 73 pp. 

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