Scientists: Cosmic Ray-Cloud Connection Explains Million-Year Climate Changes Far Better Than CO2
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 ācancel each other out.ā
CO2ās 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/mĀ² for CO2 doubling [~0.7Ā°C] rather than 3.7 W/mĀ² [1.2Ā°C] per doubling).
Assessing only millions-of-years timescales, the authors (Shaviv et al., 2023) suggest:
āThe CR/climate relationship is the only one capable of explaining the magnitude of the observed solar-climate interactions.ā
āThe apparent effect that the CRs have on cloud cover automatically explains the size of all the observed solar-related climate variations.ā
āThe seven ice-age epochsā¦over the past billion years have taken place when the CR flux was higher, as the theory predicts.ā
āDecreases in CO2 concentration and the increase in solar luminosity mostly cancel each other out.ā
Two of the 3 authors of this study documented the the large effect on climate due to ācloud radiative forcingā induced by a cosmic ray-cloud link a few years ago (Svensmark et al., 2021). They found that ālow liquid clouds are mainly responsible for the change in net radiative forcingā (i.e., 2 W/mĀ²) over short-term periods as well.
The ancient climate link to galactic cosmic ray/cloud-induced global cooling and consequent mass extinction episodes has been suggested by other scientists (Isozaki, 2019) as well.
āGalactic cosmic radiation (GCR) and solar/terrestrial responses in magnetism (Category 4) could have had a profound impact on the Earthās climate, in particular on extensive cloud coverage (irradiance shutdown).ā
āAs an ultimate cause (Category 4) for major extinction, the episodic increase in GCR-dust flux from the source (dark clouds derived from starburst) against the geomagnetic shield likely determined the major climate changes, particularly global cooling in the past.ā