Spatial patterns of climate change across the Paleocene-Eocene Thermal Maximum

The Paleocene-Eocene Thermal Maximum (PETM) is a global warming event that occurred 56 Ma in response to an increase in carbon dioxide. Geological data from the PETM are only available from a few places, which makes it difficult to get a global view of what happened. Here, we use a technique called data assimilation to create maps of PETM climate. We find that changes in temperature and rainfall during the PETM are similar to future projections of climate change. We also calculate "climate sensitivity"—how much the Earth warms when carbon dioxide levels are doubled. We find that PETM sensitivity is much higher than today, which suggests the Earth becomes more sensitive to greenhouse gas emissions as they increase.