Washington Post: Such is the result of a new study in Nature Geoscience, led by Richard Zeebe of the University of Hawaii at Manoa, and colleagues from the University of Bristol in the UK and the University of California-Riverside. By Chris Mooney
'“If you look over the entire Cenozoic, the last 66 million years, the only event that we know of at the moment, that has a massive carbon release, and happens over a relatively short period of time, is the PETM,” says Zeebe. “We actually have to go back to relatively old periods, because in the more recent past, we don’t see anything comparable to what humans are currently doing.”
'That’s why this time period is so crucial to study — as a possible window on our own.
'There’s no doubt that a lot of carbon — about as much as contained the fossil fuel reserves that humans have either already burned, or could still burn, combined — made its way into the atmosphere during the PETM. The result was a major warming event that lasted over 100,000 years. But precisely how rapidly the emissions occurred is another matter.
'“If anthropogenic emissions rates have no analogue in Earth’s recent history, then unforeseeable future responses of the climate system are possible,” the authors write.'
"Anthropogenic carbon release rate unprecedented during the past 66 million years" by Richard E. Zeebe, Andy Ridgwell, and James C. Zachos here