Here's a good place to start: ftp://ftp.cdc.noaa.gov/Datasets/20thC_ReanV2c/Monthlies/gaussian/monolevel/air.sfc.mon.mean.nc It's netcdf global monthly mean ai

Here's a good place to start: ftp://ftp.cdc.noaa.gov/Datasets/20thC_ReanV2c/Monthlies/gaussian/monolevel/air.sfc.mon.mean.nc It's netcdf global monthly mean air temps. Pick some grid points and plot time series. Have fun.