Modern-day Antarctica hardly brings beaches and sunshine to mind. But according to new research, the continent and its surroundings used to be a much balmier place. During the Eocene, about 40 to 50 million years ago, Antarctica's climate resembled the modern-day Californian coast, while nearby polar islands were more akin to Florida, Yale News reports.

The Eocene featured a greenhouse climate, the researchers describe, with high levels of carbon dioxide keeping conditions on Earth exceptionally warm. To figure out just how hot things got, the researchers turned to two isotopes found in ancient shell fossils. The concentration of bonds between those two isotopes, the researchers describe, is an indicator of the temperature at which those ancient organisms grew. Ocean currents helped determine the precise temperature at any given location, they further found.

Antarctica, they calculated, reached a high of 63F, with an average temperature of 57F. Parts of the surrounding ocean got even warmer, reaching a pleasant bathwater temperature of 72F. Today, those same averages fall well below freezing. The Eocene conditions, they say, help climate scientists "understand the sensitivity of the climate system to greenhouse gases, and especially the amplification of global warming in polar regions"—a pretty useful piece of knowledge to have as the world warms up.