Carbon burp and transient global warming during the Paleocene-Eocene Thermal Maximum

The Paleocene–Eocene Thermal Maximum (PETM), ~55.5 Myr ago, was a geologically brief (~170 kyr) episode of globally elevated temperatures that occurred superimposed on the long-term late Paleocene and early Eocene warming trend. It was marked by a 5-8°C warming in both lowand high-latitude regions, a perturbation of the hydrological cycle and a major biotic response on land and in the oceans, including radiations, extinctions and migrations (see overviews in Bowen et al., 2006; Sluijs et al., 2007a). In addition, the PETM was associated with a pronounced negative carbon isotope excursion (CIE), recorded as a >2.5‰ decrease in the stable carbon isotope composition (δ13C) of sedimentary components (e.g., Kennett and Stott, 1991; Koch et al., 1992) (Fig. 1). The CIE can only be explained by a carbon “burp”—a massive (at least 1.5×1018g; 1500 Gt) injection of 13C-depleted carbon into the ocean-atmosphere system (Dickens et al., 1995). Recent work has focused on elucidating the source and injection mechanisms of the carbon that caused the CIE, as well as on addressing the question of whether the 13C-depleted carbon caused the warming or acted as a positive feedback in an already warming world. Other questions of interest include whether the PETM was a unique event in the early Paleogene greenhouse world, and the relevance of the fossil carbon burp to the current carbon burp resulting from fossil fuel burning.