09 Aug 2019
09 Aug 2019
Status: this discussion paper is a preprint. It has been under review for the journal Climate of the Past (CP). The manuscript was not accepted for further review after discussion.

Evidence for a widespread climatic anomaly at around 7.5–7.0 cal ka BP

Mei Hou1,2,5, Wenxiang Wu1,2, David J. Cohen3, Yang Zhou1, Zhaoqi Zeng1,5, Han Huang1, Hongbo Zheng4, and Quansheng Ge1 Mei Hou et al.
  • 1Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
  • 2CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, 100101, China
  • 3Department of Anthropology, National Taiwan University, Taipei, 10617, Taiwan, China
  • 4Research Center for Earth System Science, Yunnan University, Kunming, 650091, China
  • 5University of Chinese Academy of Sciences, Beijing, 100049, China

Abstract. A climate event at 7.5–7.0 cal ka BP (thousand calibrated years before present) has been recognized. This event is important for foreseeing the possible response of the climate system to global warming and for interpreting considerable societal change, but it has heretofore lacked a systematic review. Here, we summarize previously published paleoclimate records spanning this event from 47 sites around the world. The proxy evidence from a variety of paleo-archives, including lake sediments, speleothems, marine sediments, and ice cores, provides a clear picture of this climate change. The synthesis results show a weaker Asian summer monsoon, in contrast to a stronger South American summer monsoon during the event. The event also involves dramatic cooling and wetter conditions in north-central Europe and in western North America, widespread aridity across Africa, contrasting patterns of precipitation variability throughout the Mediterranean, and notable cooling over the polar region, suggesting that it is a worldwide climate event. Comparison of paleoclimate records with climate-forcing time series gives likely climate controls for the event. The close correspondence in time of solar irradiance minima, strong volcanic eruptions, the meltwater flux into the North Atlantic, an orbitally induced decrease in solar insolation, and climate changes indicated by proxy data suggest possible linkages. More quantitative reconstructions and higher resolution climate records are needed to fully capture the magnitude, timing, duration, and nature of this event, which will be of considerable relevance to modeling.

Mei Hou et al.

Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Mei Hou et al.

Mei Hou et al.


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Short summary
Past climate change is of great scientific interest to deal with increasing global warmth. In this paper, we compile 47 paleoclimate records from locations around the world to document a climate anomaly at 7.5–7.0 cal ka BP (1 cal ka BP=1000 calibrated years before present). The synthesis suggests that the 7.5–7.0 cal ka BP event is of worldwide significance and four possible forcing mechanisms responsible for it, including orbital forcing, solar activity, volcanic eruption, and meltwater flux.