Palm plants thrived in the Arctic 53.5 million years ago, during a transient warm period known as the Eocene Thermal Maximum 2, according to a study published online this week in Nature Geoscience. The presence of these plants indicates that winter temperatures over the continents in the Arctic region were, on average, higher than eight degrees Celsius.

Appy Sluijs and colleagues used marine sediments collected from the Arctic Ocean to assess the environmental changes associated with the rapid warming during the Eocene Thermal Maximum 2. This climate event is generally attributed to a fast rise in atmospheric carbon concentrations. Their reconstructed model of sea surface temperatures peaked at a balmy 27 degrees Celsius, a three to five degrees Celsius rise over background conditions. The presence of palm pollen in the marine sediments revealed that palm plants were prevalent in the high northern latitudes.