A new international analysis of marine fossils shows that the warming of the polar oceans during the Eocene, a greenhouse period that provides a glimpse of Earth’s potential future climate, was greater than previously thought.
By studying the chemical composition of fossilized foraminifera, tiny single-celled animals that lived in shallow tropical waters, a team of researchers generated precise estimates of tropical sea surface temperatures and seawater chemistry during the Eocene Epoch, 56-34 million years ago. Using these data, researchers fine-tuned estimates from previous foram studies that captured polar conditions to show tropical oceans warmed substantially in the Eocene, but not as much as polar oceans.
Importantly, when modern climate models – the same as those used in the United Nations’ recent Intergovernmental Panel on Climate Change reports – were run under Eocene conditions, many could not replicate these findings. Instead, the models consistently underestimated polar ocean warming in the Eocene.