I downloaded monthly gridded data from this website: http://browse.ceda.ac.uk/browse/badc/cru/data
(Registration is free, but required. Once registered, go to the tab “dataset” and search for “CRU”. You will find a number of datasets. Click on “CRU TS3.23: Climatic Research Unit (CRU) Time-Series (TS) Version 3.23 of High Resolution Gridded Data of Month-by-month Variation in Climate (Jan. 1901- Dec. 2014)”, click “Data”, then chose a variable (for instance “pet”). Chose the year-period (I took 2001-2010).
The file that you have now should contain monthly grids from January 2001 till December 2010. It is a netcdf file but I do not manage to see the different years. Once I open in it Arc Gis, I don’t find a way to select the different year/month-layers. I used "multidimensional tools" in the toolbox to open the map. I found on the internet somebody else who had the same problem, but I don't understand how he solved it. I am relatively new to ArcGis. (NetCDF to Raster (arcgis) - GIS - CartoTalk )