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, 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 Resoluti
on 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 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
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, 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.
