The Post-Partisan Emporium

Per a  new study , million-year variations in cosmic rays (CR) modulating cloud cover, which, in turn, drives variations in incident solar radiation on short- and long-term timescales, is the dominant cause of million-year climate variations, explaining all 7 Ice Age epochs over the Phanerozoic. In contrast, declining CO2 and rising solar luminosity over the last billion years cannot explain past climate variations, as they “cancel each other out.” CO2’s effects on climate are, using paleoclimate estimations of solar luminosity, assessed to be nearly just half of what the climate models say they are (2.1 W/m² for CO2 doubling [~0.7°C] rather than 3.7 W/m² [1.2°C] per doubling). Assessing only millions-of-years timescales, the authors ( Shaviv et al., 2023 ) suggest: “The CR/climate relationship is the only one capable of explaining the magnitude of the observed solar-climate interactions.” “The apparent effect that the CRs have on cloud cover automatically explains the size of all the