Antarctica was once as warm as Florida, California

Parts of Antarctica - one of the coldest places on Earth - were as warm as today's California coast about 40 million years ago with temperatures as high as 17 degrees Celsius, a new study has found.
Researchers also found that the polar regions of the southern Pacific Ocean once registered 21st-century Florida heat.
The findings underscore the potential for increased warmth at Earth's poles and the associated risk of melting polar ice and rising sea levels, the researchers said.
Led by scientists at Yale University, the study focused on Antarctica during the Eocene epoch, 40-50 million years ago, a period with high concentrations of atmospheric CO2 and consequently a greenhouse climate.

Today, Antarctica is year-round one of the coldest places on Earth, and the continent's interior is the coldest place, with annual average land temperatures far below zero degrees Fahrenheit.
The new measurements can help improve climate models used for predicting future climate, according to co-author Hagit Affek, associate professor of geology & geophysics at Yale.

"Quantifying past temperatures helps us understand the sensitivity of the climate system to greenhouse gases, and especially the amplification of global warming in polar regions," Affek said.
By measuring concentrations of rare isotopes in ancient fossil shells, the scientists found that temperatures in parts of Antarctica reached as high as 17 degrees Celsius during the Eocene, with an average of 14 degrees Celsius - similar to the average annual temperature off the coast of California today.

Eocene temperatures in parts of the southern Pacific Ocean measured 22 degrees Celsius - similar to seawater temperatures near Florida today, researchers said.
Today the average annual South Pacific sea temperature near Antarctica is about zero degrees Celsius.
These ancient ocean temperatures were not uniformly distributed throughout the Antarctic ocean regions - they were higher on the South Pacific side of Antarctica - and researchers say this finding suggests that ocean currents led to a temperature difference.
"By measuring past temperatures in different parts of Antarctica, this study gives us a clearer perspective of just how warm Antarctica was when the Earth's atmosphere contained much more CO2 than it does today," said lead author, Peter MJ Douglas, now a postdoctoral scholar at the California Institute of Technology.

"We now know that it was warm across the continent, but also that some parts were considerably warmer than others. This provides strong evidence that global warming is especially pronounced close to the Earth's poles," Douglas said.
The finding was published in the journal PNAS.