Too-Hot Times: Climate warming has been invoked as a factor contributing to widespread extinction events, acting as a trigger or amplifier for more proximal causes, such as marine anoxia.Sunet al.(p.366; see the Perspective byBottjer) present evidence that exceptionally high temperatures themselves may have caused some extinctions during the end-Permian. A rapid temperature rise coincided with a general absence of ichthyofauna in equatorial regions, as well as an absence of many species of marine mammals and calcareous algae, consistent with thermal influences on the marine low latitudes. Sea surface temperatures approached 40°C, which suggests that land temperatures likely fluctuated to even higher values that suppressed terrestrial equatorial plant and animal abundance during most of the Early Triassic.

High-resolution oxygen isotope records document the timing and magnitude of global warming across the Permian-Triassic (P-Tr) boundary. Oxygen isotope ratios measured on phosphate-bound oxygen in conodont apatite from the Meishan and Shangsi sections (South China) decrease by 2‰ in the latest Permian, translating into low-latitude surface water warming of 8 °C. The oxygen isotope shift coincides with the negative shift in carbon isotope ratios of carbonates, suggesting that the addition of isotopically light carbon to the ocean-atmosphere system by Siberian Traps volcanism and related processes resulted in higher greenhouse gas levels and global warming. The major temperature rise started immediately before the main extinction phase, with maximum and harmful temperatures documented in the latest Permian (Meishan: bed 27). The coincidence of climate warming and the main pulse of extinction suggest that global warming was one of the causes of the collapse of the marine and terrestrial ecosystems. In addition, very warm climate conditions in the Early Triassic may have played a major role in the delayed recovery in the aftermath of the Permian-Triassic crisis.

Middle Permian Extinction: A major extinction in the Middle Permian 260 to 270 million years ago preceded the huge end-Permian extinction. Wignall et al. (p. 1179 ) present a detailed analysis of the Middle Permian event from rocks in southwest China. The extinction coincided with extensive nearby volcanic eruptions. A major drop in carbon isotope values followed the extinction event, implying massive disruption of the carbon cycle.