Warm/cool epochs over past 2000 years were regional until 20th century warming

Percentages of earth’s surface experiencing abnormal warm (red shading) and cold (blue shading) temperatures. Shading intensity indicates the magnitude of warmth and cold. a, Annual data. b, 51-year averaged data.

Over the last 2000 years Europe has experienced centennial scale cool and warm epochs including the Little Ice Age (1300 and 1850 CE), the Mediaeval Warm Period (800–1200 CE), the Dark Ages Cold Period (400–800 CE) and the Roman Warm Period (250 BCE to 400 CE). A recent analysis has generated spatial temporal temperature reconstructions covering the entire globe for the past 2,000 years. The research found no evidence that preindustrial cold and warm periods recorded in Europe and elsewhere extended over the entire globe. By contrast, the warmest period of the past 2,000 years occurred during the twentieth century for more than 98 per cent of the globe.

No evidence for globally coherent warm and cold periods over the preindustrial Common Era, Raphael Neukom, Nathan Steiger, Juan José Gómez-Navarro, Jianghao Wang & Johannes P. Werner, Nature, volume 571, pages 550–554 (2019).