Caving In to New Chronologies

摘要

When you check the weather forecast on TV you do not expect it to be completely accurate. But you do expect a degree of certainty about when the forecast is for: It would not be very useful to hear that it will probably be rainy, but with a thousand-year uncertainty about when. Yet this is the situation faced by those studying past climate. Records of climate from sediment or ice cores are not time series but depth series, and converting depth to age generally carries a substantial uncertainty. Thisis unfortunate because the timing of climatic changes can provide fundamental information about the mechanisms driving that change. A climate change in one region, for instance, could not have been caused by change at a later time in another region. Thissituation presents pale-oclimatologists with a dilemma. Often, the best way to constrain the chronology of a poorly dated record is to line up events in that record with those in a better dated record. But to do so discards information about the phasing of change and therefore about the links between climate in different regions, or between climate and the forces that drive it.