The original data took the form of a value for each month and each box on a 0.5 degree latitude / longitude grid. The annual values are the average of their constituent months, they have been calculated by GRID-Geneva. Original Data Station observations were first collected by national meteorological, hydrological and related services, and were acquired through the free and unrestricted exchange of meteorological and related data. These observations were gridded by collaborators at the Climatic Research Unit (www.cru.uea.ac.uk). The gridded data-set is publicly available, and has been published in a peer-reviewed scientific journal. Data Source: CRU TS 2.10 Jan 2004 T. D. Mitchell, Tyndall Centre Reference: Mitchell T.D. and Jones P.D. 2005 An improved method of constructing a database of monthly climate observations and associated high-resolution grids. Int. J. Climatol. 25: 693-712