University of East Anglia Climatic Research Unit (CRU) Global 0.5° Monthly Time Series, Version 2.1 (CRU TS 2.1)

The data are here.

A dataset of mean monthly surface data (for 1901-2002) over global land areas, excluding Antarctica. Interpolated from station data to 0.5 degree lat/lon for a range of variables: precipitation and wet-day frequency, mean, maximum, and minimum temperature and diurnal temperature range, vapor pressure, percent cloud cover, and ground-frost frequency.

Please see the CRU TS 2.1 page at the Climatic Research Unit website for the original documentation: CRU_TS_2_1.html. A pdf document that briefly explains the methods used to construct the data set can be found here: CRU_TS_2_0_intro.pdf.