via Ka Leo O Hawaii: UH Manoa Student College Newspaper & Media – Carbon dioxide not sole chemical culprit in global warming.

By Junghee Lee


Published: Thursday, July 23, 2009

Updated: Monday, August 3, 2009



With the aid of the drillship JOIDES Resolution, a team of scientists retrieved deep-sea sediments from the Atlantic, Pacific, Indian and Southern oceans. Through these findings, scientists were able to deduce that CO2 levels were actually lower than what the temperature change would indicate, suggesting that there may be more factors involved in global warming.

A team of scientists in conjunction with the University of Hawai’i department of oceanography discovered that carbon dioxide (CO2) might not be the only substance in causing global warming.

By studying an ancient global warming episode called the Paleocene-Eocene Thermal Maximum (PETM), the team observed that the anticipated CO2 levels for a temperature increase of 5 to 9 degrees Celsius was lower than expected.

“We expected a three-fold to eight-fold increase of carbon dioxide to produce this temperature increase, but what we found was less than a two-fold increase,” said Dr. Richard Zeebe, assistant professor of oceanography at UH Mānoa.

This discovery was made through the study of deep-sea sediments from the Atlantic, Pacific, Indian and Southern oceans. These sediments were recovered from the drillship JOIDES Resolution.

The team is now attempting to find the other substances that caused the earth’s rise in temperature 55 million years ago.

“If this additional warming was a response or an amplification of the initial carbon dioxide release, then future warming could be stronger than we anticipate,” said Zeebe.

The scientists first developed indicators to reconstruct previous greenhouse gas concentrations; one possible substance is methane, since it is a relatively strong greenhouse gas.

“Unfortunately, there isn’t any good indicator available at the moment to reconstruct the methane concentration,” said Zeebe. “We’re trying to develop these tools to understand this,” he added.

The team then analyzed the events before, after and during PETM to find out the general underlying mechanism of the warming. Although PETM was considered a severe warming event, there came smaller events afterwards, much like aftershocks following an earthquake.

“We are looking at the smaller events to see whether or not they have the same origins and mechanism as the PETM,” said Zeebe.

This discovery does not anticipate that CO2 is an insignificant factor in global warming.

“Carbon dioxide is a critical factor for current and future global warming,” said Zeebe. “What we are saying is that there were additional factors that contributed to the warming during this past event and we need to understand them in order to make better future predictions.”

This research was possible with funding from the National Science Foundation (NSF), the UH meteorology department and various departments of the School of Ocean and Earth Science and Technology (SOEST).

“The department’s primary role is to provide the infrastructure needed for their research, including laboratory and office space, and administrative and financial support,” said Frank Sansone, UHM oceanography department chair.

The idea of studying deep-sea sediments to discover climate changes has been proposed by various scientists in the past.

“This information can give us an idea of what kind of climatic changes are in store for us, but cannot actually predict the future,” said Sansone.