Most of us are quite comfortable with the idea of evolution in the animal kingdom or in climate, by which small departures from the norm can spread and eventually change the entire picture. We are not as ready to accept a similar evolution in classical data sets, the gold standard of climatology.
Recently, I have been using a small subset of the data generated by the GEOSECS (Geochemical Ocean Sections) program (1973–1974), in particular, the ocean profiles of oxygen-18 and deuterium measured by Harmon Craig at Scripps Institution of Oceanography in La Jolla, Calif. Until recently, I was secure in the knowledge that the data I was using, gathered from the National Climate Data Center repository, were complete and unadulterated. Earlier this year, while presenting my results and using these data for comparison, a member of the audience wondered why I was not using the complete data set. Confused, I defended myself vigorously. Later, it appeared that although I had correctly presented the published data, there was an underground version of unpublished data that was known only to a small circle of initiates. My hosts were kind enough to include me among the cognoscenti and it was at this point that things started to become interesting.