Exceptional terrestrial warmth around 4200-2800 years ago in Northwest China.

One of the Holocene abrupt events around 4200 years ago, lasting for ∼ 200 years, is thought to have caused cultural disruptions, yet terrestrial climatic status right after the cold/dry event remains poorly defined and is often presumed that a generally cool condition prevailed during the Bronze Age (∼ 4000-2200 years ago). Here we report an alkenone-based summer temperature record over the past ∼ 12,000 years, in addition to two updated alkenone records, from Northwest China, providing new insights into the climatic status right after the event. Our results indicate that exceptional terrestrial warmth, up to ∼ 6 °C, occurred around 4200-2800 years ago during the Bronze Age, superimposed on the long-term Holocene cooling trend. The exceptional warmth in Northwest China, together with other climate anomalies elsewhere, suggests an unusual large-scale climatic reorganization at 4200-2800 years ago when solar activity remained high, with important implications to the climate background for cultural developments during the Bronze Age.