Three million years ago, the concentration of sea ice in the Arctic greatly affected the land temperatures in the Pliocene era, according to new research by UM bioclimatology Assistant Professor Ashley Ballantyne.

According to a University of Montana news release, Ballantyne and coauthors used a global climate model to look at carbon dioxide concentrations, which recently reached 400 peers per million, similar to the Pliocene levels. However, at that time, according to the study in the July issue of Nature Geoscience, the Arctic surface temperatures were 15 to 20 degrees Celsius warmer than surface temperatures now.

The findings suggest that much of the surface warming was due to ice-free conditions in the Arctic. It also showed that sea ice could affect warming more than land-based ice.

Scientists have been measuring decreasing sea ice in the Arctic each year.

Ballantyne worked with his coauthors from Northwestern University, the University of Colorado and the National Center for Atmospheric Research. The full paper will be published in Palaeogeography, Palaeoecology: An International Journal for the Geosciences.