A new study has produced globally complete maps of the carbon-driven warming that occurred in the Paleocene Eocene Thermal Maximum (PETM), 56 million years ago. Changes in rainfall patterns and amplification of warming at the poles were remarkably consistent with modern trends.
The warming of the PETM was triggered by a geologically rapid release of CO2, predominantly from a convulsion of magma in Earth’s mantle at the location where Iceland is now situated. The magma invaded oil-rich sediments in the North Atlantic, boiling off methane and CO2.
As our climate warms, scientists are increasingly exploring past climates for insights, but they are hindered by uncertainties in temperature, CO2 levels and the exact timing of changes.
The researchers calculated the CO2 levels before and during the PETM. They discovered CO2 was about 1,120 ppm just before the PETM, rising to 2,020 ppm at its peak. In comparison, preindustrial CO2 was 280 ppm and we are currently at about 418 ppm.
A problem for the researchers is that they don’t have data for every place on Earth. Geological data for the PETM is limited to locations where sediments are preserved and accessible – typically using a bore hole or outcropping on land.