Eocene period holds clue to future

A new report has been released, which make public the results of an Arctic Ocean drilling expedition in 2004. The expedition allowed a team of US scientists to measure samples of biological and geological material from the beginning of the Paleocene/Eocene thermal maximum (PETM).

The PETM took place 55 million years ago and is recognised as a period of extreme carbon dioxide-induced global warming when the overall global temperature was higher and more uniform from the subtropics to the arctic, and where humidity, precipitation and salinity of the ocean water altered drastically, along with elevated global and regional temperatures over a very short period.

Ancient plant remains recovered during the expedition were used to measure carbon and hydrogen isotopes in the fossil plants remains and reconstructed the pattern of precipitation and characteristics of the ancient arctic water.

"Our results told us a lot about the way that the large-scale water cycle is affected during global warming," said Mark Pagani, professor of geology and geophysics at Yale University.

The large-scale water cycle refers to the way water vapour is transported from the tropics and subtropics to the pole regions. "It looks like a substantial increase in precipitation led to increased river runoff, lower ocean salinity, and drastically lower oxygen levels in the Arctic Ocean," suggested Mr. Pagani, who co-wrote the report.

He continued, "It is important to realize that the impact of global warming also concerns the existing water cycle. We need to anticipate big changes in patterns of precipitation as temperatures rise."

Co-author Matthew Huber, an assistant professor of earth and atmospheric sciences at Purdue University's College of Science confirmed that there now exist a "pretty good correlation between records of past warmth and higher carbon dioxide concentrations, which tells us that it's not too difficult to push the climate system to a warm state. This is what the human population is expected to do over the next few hundred years."