New findings show a slow recovery from extreme global warming episode 55 million years ago

SANTA CRUZ, CA--Most of the excess carbon dioxide pouring into the atmosphere from the burning of fossil fuels will ultimately be absorbed by the oceans, but it will take about 100,000 years. That is how long it took for ocean chemistry to recover from a massive input of carbon dioxide 55 million years ago, according to a study published this week in the journal Science.

James Zachos, professor of Earth sciences at the University of California, Santa Cruz, led an international team of scientists that analyzed marine sediments deposited during a period of extreme global warming known as the Paleocene-Eocene Thermal Maximum (PETM). Sediment cores drilled from the ocean floor revealed an abrupt change in ocean chemistry at the start of the PETM 55 million years ago, followed by a long, slow recovery.