Palaeogeographic reconstructions shape understanding of deep-time climate change

Oxygen isotope compositions (δ¹⁸O) have been widely used to reconstruct deep-time climate dynamics, which have been shown to vary through time and space. Reconstruction of the spatial pattern of these records relies on robust estimates of palaeolocations derived from Global Plate Models (GPMs). However, several different GPMs exist which vary in their palaeogeographic reconstruction, potentially impacting estimates of deep-time latitudinal temperature gradients and latitudinal-band temperatures. Since global mean temperatures are calculated as the sum of area-weighted latitudinal-band temperatures, variations in GPMs may also influence global mean temperature estimates. Here, we tested whether GPM choice impacts reconstructions of Early Palaeozoic climate by analysing an extensive Ordovician δ¹⁸O dataset compiled from bulk rocks, brachiopods, and conodonts. Using four open-access GPMs to reconstruct the paleogeographic distribution of sampled localities from our Ordovician δ¹⁸O dataset, we quantified discrepancies in palaeolatitudinal-band temperatures and global mean temperatures. Our results indicate that variations in GPM palaeogeographic reconstructions alone can lead to large differences (3–3.5°C) in palaeolatitudinal-band temperature and global-mean temperature estimates. Our findings suggest that GPM choice can substantially impact reconstructions of deep-time climate dynamics and careful consideration of the differences in palaeogeographic reconstructions between GPMs is required.