A network of interdisciplinary scholars studying past climate change
This week’s issue of Science contains a new study of ice cores from the Quelccaya ice cap in the Peruvian Andes. Thompson et al. take advantage of new measurement techniques to present an annually resolved record of past climate. The largest signal in the record is the Little Ice Age, especially during c.1520-1680AD, a period marked by particularly low oxygen isotope ratios, highly correlated to lower temperatures. Records of nitrate and ammonium ions give further clues to changes in regional circulation, including a possible southward shift in the Intertropical Convergence Zone during the Little Ice Age. However, the authors are cautious about drawing further conclusions regarding the source of these signals.