About 6 months ago, I wrote up a summary of how paleoclimatologists determine the temperature of the past, focusing primarily on oxygen isotopes Paleoclimatology Primer. It was relatively well received, so I figured I would continue the lessons on paleoclimatology. Today we will focus on the problems/opportunities inherent to the oxygen isotope system, and a few other systems that help us get a stronger handle on the climate of the past. I highly recommend you go back and read that post first, as this post builds upon what we learned 6 months ago.
As a warning, almost all of the links I have provided here require a paid subscription (with a few exceptions), but almost all of the links are from major journals (Science, Nature, Geology, etc.) and your local library is likely to have a subscription. The abstracts of each paper are always free though.