The Bray (Hallstatt) Cycle

Guest essay by Andy May and Javier

The evidence for a persistent irregular climate cycle with a period of 2400 ±200 years is strong. There is compelling evidence of a solar cycle of about the same length and phase; suggesting that the solar cycle might be causing the climate cycle. We will present a summary of the evidence, beginning with the original paleontological evidence, followed by the cosmogenic radionuclide (¹⁰Be or Beryllium-10 and ¹⁴C or Carbon-14) evidence. For more information, a bibliography of many papers discussing topics relevant to the Bray (Hallstatt) cycle can be found here. Only a small portion of the relevant papers are mentioned in this summary post.

In the November 16, 1968 issue of Nature, James R. Bray first proposed the idea of a 2600-year solar-driven climate cycle based primarily upon evidence of Holocene global glacier advances and retreats. We prefer…