The gridded Climatic Research Unit (CRU) TS (time-series) 3.21 datasets are month-by-month variations in climate over the period 1901-2012, on high-resolution (0.5 x 0.5 degree) grids, produced by the Climatic Research Unit (CRU) at the University of East Anglia. They are available from here:

This is an R package for reading in and manipulating CRU TS3.21: Climatic Research Unit (CRU) Time-Series (TS) Version 3.21 data. A test script is below