Before there were weather forecasters, there were clams.

Donna Surge, assistant professor of geological and atmospheric sciences, is studying the chemical signatures of carbon dioxide deposits in the shells of southwest Florida clams. The deposits can indicate what the climate was like during the past 2,000 years. The variations of carbon dioxide signatures indicate changes in temperature.

Climate measurements began being recorded in Europe about 100 years ago, Surge said. The research will help scientists estimate what climates were like before they were recorded.

“The importance of the project is we are in a present state of global warming,” Surge said. “We don’t know how much humans are contributing to that … We are looking at chemical variations in the shells as an indicator of changes in temperature.”

Long-term research in Florida and Denmark has led Surge and her colleagues to find clam shells in trash piles from ancient cultures, called “middens,” which will help Surge find past climate patterns and changes. The Florida and Denmark locations will allow Surge to compare climates around the world.

“Climate patterns are not just local patterns,” Surge said.

“There are connections in other regions, and so that’s one of the things that’s important about doing the work in southwest Florida: to see what other connections there are at other regions of the globe.”

The benefit of using clams in this research is that their shells are similar to tree rings. The layers or rings of the shell can be dated, Surge said.

She also said she looks at ear bones in fish for chemical signatures of past water data.

The carbon dioxide concentrations and their different chemical signatures will be the indicator of human involvement in global warming, Surge said.

There are substantial consequences to climate changes, said Carl Jacobson, professor and chairman of geological and atmospheric sciences.

Climate changes can affect agriculture, ocean levels and world dynamics.

“There used to be a view that climate changes have been very gradual, but it has been studied that climate changes can happen in just a few years,” Jacobson said. “A drastic period of climate change could change world dynamics.”

The National Science Foundation awarded the project a three-year grant of $364,000. Other funds for the research are distributed from the College of Liberal Arts and Sciences and Petroleum Research Fund through the American Chemical Society.

Surge works with colleagues at the Florida Museum of Natural History and the Randell Research Center in Florida for her research.

Surge will present her research in August at the 32nd International Geosciences Congress in Florence, Italy.