Faculty Finds Strongest Evidence Yet of Link Between CO2 and Global Temperature Change

In a paper published in the March 29 issue of Nature, Dana Royer, assistant professor of earth and environmental sciences, and two colleagues from Yale University have used nearly 500 data points to create the most comprehensive model of the relationship between CO2 and temperature to date. The findings indicate that over the last 420 million years increases in CO2 in the atmosphere have had a direct and calculable relationship to increases in global surface temperatures.

The study provides the strongest and most conclusive evidence to date that, in the history of the Earth, rises in atmospheric CO2 concentrations are directly linked to increases in global surface temperatures.

Specifically, what Royer and his co-investigators found was that every doubling of atmospheric CO2 concentrations resulted in an approximately 3° C (approx 5 ° F) increase in global surface temperature. This ratio is consistent with shorter-term models and surveys.

Of course, identifying accurate data points for atmospheric CO2 are what make studies such as these difficult. Before approximately 50 years ago, there were no atmospheric CO2 measurements made directly by human beings. However, scientists have been able to use a variety of methods that rely on studies of soil, sediments, sea beds, and even fossils.

“One method involves analyzing the stomata of certain kinds of fossilized plants,” Royer says. “When the CO2 concentrations are higher, plants will have fewer pores for gas exchange. When it is lower, these plants will have more pores. This information can be combined with what we know about the temperature and other environmental factors from that period in a particular kind of modeling.”

Royer and his fellow researchers were able to draw together the data generated from a variety of methods to create their study.