Journal Article

No evidence for globally coherent warm and cold periods over the preindustrial Common Era

Werner, Johannes P., Steiger, Nathan, Gómez-Navarro, Juan José, Neukom, Raphael, Wang, Jianghao

2019

Overview

Earth’s climate history is often understood by breaking it down into constituent climatic epochs 1 . Over the Common Era (the past 2,000 years) these epochs, such as the Little Ice Age 2 – 4 , have been characterized as having occurred at the same time across extensive spatial scales 5 . Although the rapid global warming seen in observations over the past 150 years does show nearly global coherence 6 , the spatiotemporal coherence of climate epochs earlier in the Common Era has yet to be robustly tested. Here we use global palaeoclimate reconstructions for the past 2,000 years, and find no evidence for preindustrial globally coherent cold and warm epochs. In particular, we find that the coldest epoch of the last millennium—the putative Little Ice Age—is most likely to have experienced the coldest temperatures during the fifteenth century in the central and eastern Pacific Ocean, during the seventeenth century in northwestern Europe and southeastern North America, and during the mid-nineteenth century over most of the remaining regions. Furthermore, the spatial coherence that does exist over the preindustrial Common Era is consistent with the spatial coherence of stochastic climatic variability. This lack of spatiotemporal coherence indicates that preindustrial forcing was not sufficient to produce globally synchronous extreme temperatures at multidecadal and centennial timescales. By contrast, we find that the warmest period of the past two millennia occurred during the twentieth century for more than 98 per cent of the globe. This provides strong evidence that anthropogenic global warming is not only unparalleled in terms of absolute temperatures 5 , but also unprecedented in spatial consistency within the context of the past 2,000 years. Warm and cold periods over the past 2,000 years have not occurred at the same time in all geographical locations, with the exception of the twentieth century, during which warming has occurred almost everywhere.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 704/106/413 / 704/106/694 / Anthropogenic factors / Climate change / Climate variability / Coherence / Cold / Cold Temperature / Earth, Planet / Glacial epoch / Global warming / Global Warming - history / Global Warming - statistics & numerical data / History, 15th Century / History, 16th Century / History, 17th Century / History, 18th Century / History, 19th Century / History, 20th Century / History, 21st Century / History, Ancient / History, Medieval / Hot Temperature / Human Activities / Humanities and Social Sciences / Ice ages / Ice Cover / Industry - history / Industry - statistics & numerical data / Letter / Little Ice Age / multidisciplinary / Natural history / Paleoclimate / Paleoclimatology / Proxies / Science / Science (multidisciplinary) / Spatio-Temporal Analysis / Temperature extremes / Time series