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International research team to explore whether the loss of CO2 caused earth to cool 3 million years ago

NSF Grant Funds Climate Change-in-Reverse Project

Scientists at the University of Rochester expect to learn more about the role of CO2 in climate change through a study of reverse global warming— by researching the first ice sheets formed in the Northern Hemisphere.

The National Science Foundation (NSF) has awarded $4.24 million to Carmala Garzione and John Tarduno, both professors of earth and environmental sciences, to launch the joint U.S.-China research project.

“While there are several hypotheses for the onset of cooling, each one has its problems,” said Garzione. “A decrease in atmospheric CO2 provides the most straightforward explanation.”

Garzione and her colleagues will test their theory for why the planet began cooling three million years ago: that iron-rich dust from Asian deserts may have fertilized the North Pacific Ocean, stimulating the growth of algae that reduced atmospheric CO2 and ultimately caused the big chill.

“The depletion of atmospheric CO2, in turn, would have led to a cooler climate that may have made conditions even more arid,” said Garzione.” And that would have resulted in a cycle of increased dust, more iron deposits in the ocean, the further loss of CO2, and continued cooling.”

Garzione and her colleagues expect the results of their work to provide additional insights. “We hope our research will give us a more precise understanding of the role that CO2 plays in climate change,” she said. “And that knowledge may help us address questions related to the current increase in both CO2 and global temperatures.”

A key question, according to Garzione, is whether there was a “tectonic trigger”—such as the growth of mountain ranges on the northern margin of Tibet—that caused isolated basins to become arid between these ranges, as well as an increase in the amount of airborne dust.

Garzione’s colleague John Tarduno will evaluate the algal growth that’s associated with the deposition of the dust from the Asian deserts. “A central test of our hypothesis involves timing,” he said. “Specifically, is there a correlation between the release of dust from the deserts and the buildup of sediments in the ocean?”

Along with addressing questions about the formation of ice sheets in the Northern Hemisphere, the joint U.S.-China research project will provide unique educational opportunities for students on the two continents. The NSF grant will fund summer schools, workshops, and research exchanges between U.S. and Chinese students that will give them access to shared research facilities in both countries, as well as field localities in China.

“We expect the program to establish a new generation of scientists who will continue working together long after the grant runs its course,” said Garzione.

The research team includes three Chinese institutions and six other U.S. universities (Brown, Columbia, Massachusetts Institute of Technology, University of Arizona, University of Colorado, and University of Texas at Austin).

The Chinese researchers are seeking a companion award from their country’s Ministry of Science and Technology.

The grant money makes it possible to assemble a diverse group of international researchers to address this longstanding problem, said Garzione.

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