Large 14C excursion in 5480 BC indicates an abnormal sun in the mid-Holocene

Fusa Miyake, A. J.Timothy Jull, Irina P. Panyushkina, Lukas Wacker, Matthew Salzer, Christopher H. Baisan, Todd Lange, Richard Cruz, Kimiaki Masuda, Toshio Nakamura

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


Radiocarbon content in tree rings can be an excellent proxy of the past incoming cosmic ray intensities to Earth. Although such past cosmic ray variations have been studied by measurements of 14C contents in tree rings with ≥10-y time resolution for the Holocene, there are few annual 14C data. There is a little understanding about annual 14C variations in the past, with the exception of a few periods including the AD 774-775 14C excursion where annual measurements have been performed. Here, we report the result of 14C measurements using the bristlecone pine tree rings for the period from 5490 BC to 5411 BC with 1- to 2-y resolution, and a finding of an extraordinarily large 14C increase (20‰) from 5481 BC to 5471 BC (the 5480 BC event). The 14C increase rate of this event is much larger than that of the normal grand solar minima. We propose the possible causes of this event are an unknown phase of grand solar minimum, or a combination of successive solar proton events and a normal grand solar minimum.

Original languageEnglish (US)
Pages (from-to)881-884
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number5
StatePublished - Jan 31 2017


  • Cosmic ray event
  • Grand solar minimum
  • Radiocarbon
  • Solar proton event
  • Tree rings

ASJC Scopus subject areas

  • General


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