The evidence for and against astronomical impacts on climate change and mass extinctions: A review

TL;DR

This review critically examines the evidence linking astronomical phenomena, such as Galactic motions and impacts, to climate change and mass extinctions, concluding that current evidence is weak and methodological flaws are common.

Contribution

It provides a comprehensive critical assessment of the mechanisms and evidence for astronomical influences on Earth's climate and extinctions, highlighting methodological issues and the lack of strong periodic signals.

Findings

Little evidence for periodicities in biodiversity and climate over tens to hundreds of Myr

Galactic midplane and spiral arm crossings have minimal impact on climate and extinctions

Many studies suffer from flawed methodologies and incorrect hypothesis testing

Abstract

Numerous studies over the past 30 years have suggested there is a causal connection between the motion of the Sun through the Galaxy and terrestrial mass extinctions or climate change. Proposed mechanisms include comet impacts (via perturbation of the Oort cloud), cosmic rays and supernovae, the effects of which are modulated by the passage of the Sun through the Galactic midplane or spiral arms. Supposed periodicities in the fossil record, impact cratering dates or climate proxies over the Phanerozoic (past 545 Myr) are frequently cited as evidence in support of these hypotheses. This remains a controversial subject, with many refutations and replies having been published. Here I review both the mechanisms and the evidence for and against the relevance of astronomical phenomena to climate change and evolution. This necessarily includes a critical assessment of time series analysis techniques and hypothesis testing. Some of the studies have suffered from flaws in methodology, in particular drawing incorrect conclusions based on ruling out a null hypothesis. I conclude that there is little evidence for intrinsic periodicities in biodiversity, impact cratering or climate on timescales of tens to hundreds of Myr. Furthermore, Galactic midplane and spiral arm crossings seem to have little or no impact on biological or climate variation above background level. (truncated)