claim: Peer-reviewed studies, geologic records, and all the studies have shown that we have actually cooled since the Roman Warming Period, and likely since the Medieval Warming Period.
evidence: Of course, our understanding of millenial temperatures has improved greatly. The reconstructions extend further back than they did originally. The analysis methods have improved, so we have more confidence in the results. We can use many different proxies to reconstruct these temperatures, so have better spatial and temporal resolution. This allows for an improved understanding of variability and of the role of both internal and external perturbations. However, the big picture has changed little. A warm period about 1000 years ago, typically referred to as the Medieval Warm Period, a general cooling towards what is referred to as the Little Ice Age, and then the modern warm period, that appears unprecedented in the last 1000 years, or so. I think it’s important to realise that all of this is part of the normal scientific process. Early work will have limited data and will often use methods that have not been tried before. With time, we collect more data, develop improved methods, and – consequently – improve our understanding. We might even conclude that some of the early work used methods that we’d no longer regard as suitable. This doesn’t suddenly invalidate the earlier work, or imply kind of some nefarious intent. It seems pretty clear that the big picture presented by the early millenial temperature reconstructions have stood the test of time. I hope I, one day, have a paper that is still relevant, and being discussed, 20 years after being published.