Fig. 1: Late Palaeozoic proxy records of climate and seawater chemistry.

a–d, Time-calibrated (GTS 2020) compilation of published and new carbon isotopes (δ¹³C) (a), oxygen isotopes (δ¹⁸O) (b), radiogenic strontium isotopes (⁸⁷Sr^/86Sr) (c) and boron isotopes (δ¹¹B) (d) from preserved brachiopod calcite interpolated with Gaussian process smoothing (showing mean values and 16% and 84% as well as 5% and 95% confidence levels). The error bars show analytical uncertainty (2 s.d.); 0.2‰ in this study and, thus, smaller than symbol size. Previously published carbonate δ¹⁸O compilation from ref. ⁴⁷ and brachiopod δ¹¹B (with 2 s.d.) from refs. ^23,48 are shown for comparison. e, Our boron-derived CO₂ plotted alongside previously published CO₂ estimates from soil carbonate- and fossil leaf-based proxies shown with 16% and 84% confidence intervals (ref. ¹³ provides new terrestrial CO₂ as well as updated values for large part of data compiled in ref. ¹ for this time interval). The solid line and blue shading show CO₂ evolution that does not consider the effect of temperature on CO₂ calculation, and the dashed line and red shading show CO₂ evolution considering ~9 °C global warming in the Early Permian (‘Temp.’, temperature scenario). f, The number of documented glacial deposits (from ref. ⁵). g, The extent of tropical coal forests (10³ km²; from ref. ³⁰). h, Documented LIPs (following refs. ^{38,39,40,41,42}) at their approximate latitudes, with major eruptive phases indicated by black bars. Note that the distribution of glacial deposits and coal forests should be taken as approximate; the paucity of the sedimentary record and the nature of the data make their spatiotemporal distribution and uncertainty difficult to constrain. Stratigraphic column according to International Chronostratigraphic Chart 2023/9 (https://stratigraphy.org/chart). SCLIP, Skagerrak-Centred LIP; Guad., Guadalupian.