Two to 5 million years ago, oceans were 50 feet higher, icecaps were smaller and CO2 levels were about the same as today during Pliocene epoch. Researchers at the University of Arizona are using ancient plankton to help predict climate in the near future.

It took more than 2 million years for CO2 levels from the Pliocene epoch to naturally decline from 400 to 180 parts per million before the Industrial Revolution. Now just about 150 years later, CO2 levels are back up to their Pliocene heights. 

Jessica Tierney, a University of Arizona researcher, is part of a team studying ancient plankton fat to predict climate in the near future.

“There's this type of plankton in the ocean, and they change the structure of their fat actually, in response to how hot or cold the water is. And we can actually grow these guys today in a lab and watch this happen," Teirney said. "The good news is that fat doesn't break down very easily. So it's actually preserved in ancient sediments from the Pliocene. So we can isolate it and look at the structure and actually get a temperature back out.”

Tierney said in the Pliocene, temperatures warmed the western Pacific Ocean 2 degrees Fahrenheit and the eastern Pacific Ocean 5 degrees Fahrenheit. She said she expects this warming and more rainfall to happen this century, but that sea level increases would happen outside our lifetime.