Ice core data (blue/red): ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/vostok/deutnat.txt
Direct measurement (green): ftp://ftp.ncdc.noaa.gov/pub/data/anomalies/annual.land_ocean.90S.90N.df_1901-2000mean.dat
Thanks. I sometimes wonder that ice core records are not like political polls in the sense that it may be a good way to see movement, but how can we be sure its calibrated for conditions in the past that may have been different than current conditions. In particular I am wondering how much regression analysis is done to make the transition from direct measurement vs less direct methods. How much interpretation and guess work goes into making a smooth transition between the types of measurement? How do we make sure that a sloppy analysis like the infamous Mann hockey stick isn’t contrived in whatever data we view...whether it is favorable to our own point of view or not? Alas, I am wondering, but don’t have time or inclination enough to investigate...putting it on the back burner and getting back to work...