Comparing carbon emission and sequestration during two ancient hyperthermal events: the PETM and the end-Permian mass extinction

Anthropogenic carbon emission rate has exceeded 10 Pg C yr^-1 in 2020 (1), which is likely unprecedented in the last 252 million years. Studying ancient hyperthermal events may help us better understand the natural processes of carbon emission and sequestration, informing policy and decision-making to cope with climate change. Two ancient hyperthermals that occurred at the end of the Permian period and the end of the Paleocene Epoch have been studied extensively, but a key question remains: why is the end-Permian hyperthermal related to the largest mass extinction and a much-delayed recovery, yet the PETM is associated with only extinction of benthic foraminifera and a rapid recovery? I hypothesize that the life extinction and recovery patterns across these two hyperthermals are regulated by the carbon emission and sequestration rates, and the cumulative quantities of CO₂ released. Emission rate is dependent on CO₂ source (e.g., methane hydrate, thermogenic methane, marine or terrestrial organic matter, or volcanic CO₂), and sequestration rate is dependent on the location (marine vs. terrestrial) and processes (silicate weathering vs. organic carbon burial) of carbon sequestration, which are largely uncertain. These uncertainties pose difficulties in unraveling the underlying mechanisms of the different extinction patterns. Here, I quantitatively compare the carbon emission and sequestration rates of the two hyperthermals, which allows for hypothesis regarding carbon sources and sinks to be tested.