ph d. research was about i wasn't actually studying climate change for my ph d. i was focused on natural climate variability i was trying to understand long term oscillations natural oscillations in the climate and the impacts that they have and it was my interest in studying these long term oscillations that led me to try to make use of some of the long term records that we have we only have about one hundred years of instrumental or monitored measurements that doesn't really tell us how unusual the the warming we see over the past century is in the long term context we need to turn to things like tree rings and corals and ice cores all proxy data and so was my interest in these long term oscillations that led me to study those types of data and what they could tell us about longer term changes in the climate and what did they tell us well we were led sort of in this capably to this conclusion when we analyze the information in these data that there was something unusual about the warming of the past century that it really was without precedent as far back as we