Acronym in geology and climate science: PETM for Paleocene-Eocene Thermal Maximum

In earth science and climatology, PETM stands for Paleocene-Eocene Thermal Maximum. This is a transient climate perturbation, associated with a brief, but intense, interval of global warming at the end of the Paleocene (65-56 mya) and the beginning of the Eocene (56-34 mya) [1,2]. Dissociation of  oceanic methane hydrate has been hypothesized as a cause, but various other factors need to be considered [3].

The PETM as a global warming event is often compared with current global warming trends. Lee R. Kump illustrates that global temperature is rising much faster today (1 to 4 °C per 100 years) than it did during the PETM (0.025 °C per 100 years) [2]. He explains that, based on the fossil record, one can conclude that the speed of climate change has a much greater ecological impact than the extent of change, because adjusting to rapid climate change is very difficult for most biological species.     


References and further reading
[1] U. Röhl, T. Westerhold, T. J. Bralower and J. C. Zachos: On the duration of the Paleocene-Eocene thermal maximum (PETM). Geochemistry, Geophysics, Geosystems December 2007, 8 (2), 13 pages [www.es.ucsc.edu/~jzachos/pubs/Roehl_etal_07.pdf].
[2] L. R. Kump: The Last Great Global Warming. Sci. Am. July 2011, 305 (1), 56-61 [www.scientificamerican.com/article.cfm?id=the-last-great-global-warming].
[3] J. A. Higgins and D. P. Schrag: Beyond methane: Towards a theory for the Paleocene-Eocene Thermal Maximum. Earth and Planetary Science Letters 2006, 245, 523-537 [environment.harvard.edu/docs/faculty_pubs/schrag_beyond.pdf].