IPCC Climate Change Data: 1961-1990, Cloud Cover

From the IPCC website: The CRU Global Climate Dataset available through the IPCC DDC consists of a multi-variate 0.5 degree latitude by 0.5 degree longitude resolution mean monthly climatology for global land areas, excluding Antarctica, strictly constrained to the period 1961-1990. The mean 1961-1990 climatology comprises a suite of eleven surface variables: precipitation (PRE) and wet-day frequency (WET); mean, maximum and minimum temperature (TMP, TMX, TMN); diurnal temperature range (DTR); vapour pressure (VAP;) global radiation (RAD;) cloud cover (CLD); frost frequency (FRS); and wind speed (WND). The mean climate surfaces have been constructed from a new dataset of station 1961-1990 climatological normals, numbering between 19,800 (precipitation) and 3615 (windspeed). The station data were interpolated as a function of latitude, longitude and elevation using thin-plate splines. The accuracy of the interpolations are assessed using cross-validation and by comparison with other climatologies. this data-set has been decsribed in: New,M., Hulme,M. and Jones,P.D. (1999) Representing twentieth century space-time climate variability. Part 1: development of a 1961-90 mean monthly terrestrial climatology J.Climate 12, 829-856