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 ar eas and averages for the Northern and Southern Hemispheres and the Globe. Until the development of the internetthese 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 Ashe ville, 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 earl ier 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 de veloping the gridded datasets has been described in numerous publications in the climate li terature (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 scie ntists 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 ori ginal 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 dur ing 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 st ated that we would not make the data available to third parties. We included such statements as standar d 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 se ries available because of restrictions imposed by some of the data providers. A series of workshops (see Pete rson 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 i f they restrict access to their digital climate archives. A third example is the Global Precipi tation Climatology Centre ( http://gpcc.dwd.de ), run by the German Weather Service (DWD) who make various versi ons of gridded precipitation datasets freely available, but due to restrictions i mposed by data providers are not able to give access to any of the station monthly precipitation totals. The probl em is a generic issue and arises from the need of many NMSs to be or aim to be cost neutral (i.e. s ell 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. Sometim es 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, Page 1 of 4 CRU Data Availability

7/23/2010 http://www.cru.uea.ac.uk/cru/data/availability/organizations and scientists. We point enquirers to the GHCN web sit e. 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 charac terise global- and regional- scale changes. Hence, restricting the grids to only including station data thatcan 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 covere d 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 r eceived into existing series or begun new ones, so it is impossible to say if all stati ons within a particular country or if all of an individual record should be freely available. Data storage availabil ity 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 onl y the value- added (i.e. quality controlled and homogenized) data. The priorities we use when mergi ng data from the same station from different sources are discussed in some of the liter ature 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 importa nt. 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 diffic ult 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 f or site moves, instrument improvements and changes in the way averages are calculated) availabl e 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/map

doc/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 a nd charge for access (see the earlier discussion related to KNMI and GPCC).

The HadCRUT3 product is a blend of land surface (CRUTEM3) and sea sur face temperatures (HadSST2), CRU developing the land series and the Hadley Centre the S ST 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 ye ars. A similar set of publications on the Hadley Centre site document the development of the SST datasets.



## Files

 Data agreements


## References Page 2 of 4 CRU Data Availability

7/23/2010 http://www.cru.uea.ac.uk/cru/data/availability/ Hulme, M., 1994: The cost of climate data: A European experience. W eather 49 , 168-176.

 Peterson, T.C. and Manton, M.J., 2008: Monitoring changes in climate ext remes: a tale of international collaboration. Bull. Amer. Meteorol. Soc

. 89 , 1266-1271. 

## Literature describing the development of CRU land t emperature 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., K elly, 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 Hemi sphere 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 tempera ture 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 temperat ure 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 Di az, 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, Page 3 of 4 CRU Data Availability

7/23/2010 http://www.cru.uea.ac.uk/cru/data/availability/T.M.L., Bradley, R.S. and Diaz, H.F., 1985: A Grid Point Surfac e Air Temperature Data Set for

the Northern Hemisphere, U.S. Dept. of Energy, Carbon Dioxide Resear ch Division, Technical Report TRO22 , 251 pp.

 Jones, P.D., Raper, S.C.B., Cherry, B.S.G., Goodess, C.M. a nd Wigley, T.M.L., 1986: A Grid Point Surface Air Temperature Data Set for the Southern Hemisphe re, 1851-1984, U.S. Dept. of Energy, Carbon Dioxide Research Division, Technical Report TR027 , 73 pp. Page 4 of 4 CRU Data Availability

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