Huge amounts of carbon dioxide were dumped into the atmosphere by volcanoes.
Humans have poured carbon dioxide into the atmosphere over the last 250 years and this time period is often used as a parallel for our own future under climate change.
The team, led by UArizona geosciences professor Jessica Tierney, combined temperature data and climate models to confirm that the PETM is a good indicator of what will happen to the climate under future carbon dioxide level projections.
We were somewhat surprised to find that the climate changes we reconstructed shared a lot of similarities with the predictions made in the latest report of the Intergovernmental Panel on Climate Change.
Our future is characterized by faster warming at the poles than the rest of the globe, as well as stronger monsoons, more intense winter storms and less rain at the edges of the tropics. As more carbon dioxide is pumped into the air, the climate becomes more sensitive than previously thought.
Our work helps to understand our future under climate change. The basics of climate change, such as polar amplification, are features of high greenhouse gas climates both past and future.
Combining proxy temperature data with climate models was used to build the maps of the PETM. Paleoclimatologists can deduce temperatures from the past by analyzing some types of fossils. The proxy temperature data allowed for the creation of global temperature maps of the PETM.
Climate models used to create the maps of the past can be used to make future predictions. They were used to create simulations of what Earth looked like millions of years ago.
We ran simulations at different levels of carbon dioxide, ranging from 850 parts per million to a really high value of 3,000 parts per million, because those are all. Carbon dioxide in our atmosphere is about 400 parts per million and it was about 300 parts per million before the Industrial Revolution. We narrowed down the simulations to the ones that best matched the evidence.
The climate in more recent times has been reconstructed using this method.
The new study is more precise in estimating how much the globe warmed. The time period prior to the PETM was warmer than the current one. The climate is more sensitive to increases in carbon dioxide than previously thought, according to research by Tierney.
Climate sensitivity is how warm the planet gets.
If climate sensitivity is high, then we'll see more warming by the end of the century than if it's low. 2 to 5 degrees Celsius per doubling of carbon dioxide is the prediction by the Intergovernmental Panel on Climate Change. The sensitivity was found to be between 5.7 to 7.4 degrees Celsius per doubling, which is much higher than the average.
The planet will get more sensitive to carbon dioxide, which is important for thinking about longer-term climate change, beyond the end of the century.
More information: Jessica E. Tierney et al, Spatial patterns of climate change across the Paleocene–Eocene Thermal Maximum, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas.2205326119 Journal information: Proceedings of the National Academy of Sciences
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