Cryospherology is the study of the planet’s ice. Scientists in this field gather data from a variety of sources, including ice cores that are pulled from deep within glaciers, in order to study the climate record that is preserved in the countless layers of ice over the millennia.

Ice cores collected in Greenland seem to indicate a rise in carbon dioxide when compared against earlier eras in history, though the impact of the increased carbon is highly contested.

Additionally, scientists have found that Greenland’s glaciers were previously much smaller, and have had periods of great fluctuation in size over the millennia.

Furthermore, DNA sequencing shows that Greenland was once covered in trees that were wiped out by an ice age and have never regrown there.

Lastly, polar researchers–a century ago–found fossil evidence in Greenland for tropical plants and trees dating to the area’s distant past under much more tropical climate conditions.