VARIABILITY OF A STABLE SUN SINCE 255 MA

At the time of his death, Roger Yates Anderson (1927-2021) was working on a manuscript about the role of the Sun in climate change. The paper was an all-consuming passion for a decade and a sequel to his article “Enhanced climate variability in the tropics: a 200 000 yr annual record of monsoon variability from Pangea’s equator” (Climate of the Past, 2011). Making use of the Permian Castile evaporites that he had studied since the late 1950s, he identified frequencies of tropical temperature variability 255 million years ago and related them to late Pleistocene and Holocene records from the tropics and high latitudes. Finding cycles in Castile varve thickness with Gleissberg (88 yr), Maunder-Sporer (~190-~220 yr), Hale (22-26 yr), and Schwabe (11 yr) periods, he argued that the Sun has exhibited remarkably stable behavior over at least the last quarter billion years and called on gravitational interactions between it and the planets to regulate cycles in its magnetic field that somehow contributed to temperature changes on Earth. While he couldn’t determine a direct causal mechanism between the solar fluctuations and climate, he asserted that his data proved that such a link exists. He further noted the existence of a quasi-bi-millennial oscillation that switched between ~2.3 and ~1.5 kyr periods throughout the ~200,000 years recorded by the Castile. Given that these periods are consistent with the pacing of Hallstatt and Dansgaard-Oeschger oscillations recorded in Greenland ice cores and in speleothems that recorded monsoon strength in the tropics during the Holocene, he argued that past explanations for these cycles that invoked thermohaline circulation changes seem less likely given the entirely different oceanic circulation during the Permian. Instead, he argued that similarly paced ¹⁰Be and Δ¹⁴C variability in the GRIP and GISP2 ice cores and in the tree ring record indicate a solar origin for these cycles. We present Roger’s final manuscript here to transmit his ideas to the paleoclimatologic community, and to remind researchers of the extraordinary annual recording of climate found in the Castile evaporites and of Roger’s data, which we plan to release in coming months. We hope also to entice the community to search for the mechanism responsible for converting solar magnetic activity into climate response.