Abstract
Abstract Paleotemperature proxy records are widely used to reconstruct the global climate throughout the Phanerozoic and to test macroevolutionary hypotheses. However, the spatial distribution of these records varies through time. This is problematic because heat is unevenly distributed across Earth's surface. Consequently, heterogeneous spatial sampling of proxy data has the potential to bias reconstructed temperature curves. We evaluated the spatiotemporal evolution of sampling using a compilation of Phanerozoic δ18O data. We tested the influence of variable spatial coverage on global estimates of paleotemperature by sampling a steep “modern-type” latitudinal temperature gradient and a flattened “Eocene-type” gradient, based on the spatial distribution of δ18O samples. We show that global paleotemperature is overestimated in ∼70% of Phanerozoic stages. Perceived climatic trends for some intervals might be artifactually induced by shifts in paleolatitudinal sampling, with equatorward shifts in sampling concurring with warming trends, and poleward shifts concurring with cooling trends. Yet, the magnitude of some climatic perturbations might also be underestimated. For example, the observed Ordovician cooling trend may be underestimated due to an equatorward shift in sampling. Our findings suggest that while proxy records are vital for reconstructing Earth's paleotemperature in deep time, consideration of the spatial nature of these data is crucial to improving these reconstructions.
Highlights
The geological record provides critical context for understanding past, current, and future climate change (Burke et al, 2018) and its effect on biodiversity (e.g., Mannion et al, 2015)
This issue is further complicated by the strength of the latitudinal temperature gradient varying over geological time scales, with a flattened gradient recognized for some intervals, such as in the late Mesozoic and early Paleogene (Zhang et al, 2019)
Stage-level analyses of δ18O samples indicate that paleolatitudinal sampling is spatiotemporally heterogeneous
Summary
The geological record provides critical context for understanding past, current, and future climate change (Burke et al, 2018) and its effect on biodiversity (e.g., Mannion et al, 2015). Measurements of the ratio of stable isotopes 18O and 16O (δ18O) from fossils provide the most comprehensive paleotemperature record of the Phanerozoic (Veizer and Prokoph, 2015; Song et al, 2019; Grossman and Joachimski, 2020). Incomplete and heterogeneous sampling of this gradient can lead to misleading reconstructions of global paleotemperature, and temporal variation in the spatial distribution of samples might produce artifactual temperature trends. This issue is further complicated by the strength of the latitudinal temperature gradient varying over geological time scales, with a flattened gradient recognized for some intervals, such as in the late Mesozoic and early Paleogene (Zhang et al, 2019)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
