Fig.1. Banded sedimentary rock layers in Wyoming were drilled and sampled to obtain details of global warming (Credit: Scott Wing, Smithsonian Institution)
About 55.5 million years ago, the Earth experienced a period of sudden warming triggered by two rapid, immense releases of carbon dioxide into the atmosphere. This event, known as the Paleocene-Eocene thermal maximum (PETM), was originally thought to have occurred at either too slow or too fast a rate to be useful for addressing our own climate problems. The PETM was marked by temperature increases of 5℃ to 8℃ (9℉ to 15℉), along with a rise of sea levels, ocean acidification (seen in previous post), and extinction of deep sea organisms. Although most species survived and even flourished, it took 200,000 years for the world to recover from such high temperatures and carbon dioxide levels. New research suggests, however, that the PETM carbon emission rate may be close enough to hold lessons on modern global warming.
