Understanding the Past to Better Predict Climate Change
Researchers at the University of Missouri hope that gaining an understanding of major changes in the Earth’s climate in the distant past can improve climate modeling to better predict the future direction of climate change. Fourth-year geologic sciences doctoral student Page Quinton, whose area of expertise is paleoclimatology, has been studying carbon and oxygen isotopes in rocks from the Ordovician Period. The Ordovician Period lasted almost 42 million years, beginning 485 million years ago and ending 443 million years ago. Quinton says by examining the changes in the ratio of different carbon and oxygen isotopes in rocks from this period through the use of a mass spectrometer, she has seen evidence of relatively rapid changes in carbon cycling that could be related to a drawdown in atmospheric carbon dioxide, resulting in an ice age.
“As paleoclimatologists, we differ from ‘modern’ climatologists in that we can look at much longer intervals of time, and we can look at time periods when the Earth’s system was vastly different from now,” Quinton says. “During the Ordovician, CO2 levels were much, much higher than they are now, and most of the period was spent in greenhouse conditions—really warm average global temperatures with high atmospheric CO2 levels. But at the end of this period, there was a climatic shift related to a declining atmospheric CO2 level that was relatively rapid and led to an ice age.” Quinton says she is trying to understand when the drawdown of atmospheric CO2 happened and whether that triggered the second largest mass extinction event in Earth’s history.
What might have caused the drawdown in atmospheric CO2?
“One hypothesis we are testing is whether there was an increase in primary (plant) productivity,” Quinton says. “ So think of huge algae blooms—those organisms then die, fall to the sea floor and get buried, and by burying organic matter formed by photosynthesis you are basically burying CO2, which will drawdown atmospheric CO2.”
Quinton recently published a paper on her findings, “Carbon Cycling Across the Southern Margin of Laurentia During the Late Ordovician.” Her adviser, Professor Ken MacLeod, says the thing researchers get in the deep time record is the exact same Earth, the exact same physics, yet under vastly different conditions.
“So if our understanding of climate today also explains our observations of the past, we have more confidence that we understand how Earth’s climate system works, and then that feeds back to the people who work on climate models in decade to century to millennial time scales,” MacLeod says.
Quinton’s research was partially funded by a grant from the National Science Foundation.