PETM – Unearthing Ancient Climate Change – Science Bulletins – AMNH

Scientists have a few hypotheses but no theory has yet emerged about a significant bio-geological event that happened fifty-five million years ago. What we know for sure was that there was a sudden, enormous influx of carbon that has dissolved in the ocean and atmosphere. As atmospheric CO2 content increased, the average global surface temperature rose 5°C to 9°C (9°F to 16°F). This global warming event is called the Paleocene-Eocene Thermal Maximum (PETM) and lasted for 170,000 years. Events triggered large changes in composition of biological communities.

A large collaborative team of paleontologists, paleobotanists, soil scientists, and other researchers take us to the field in Wyoming’s Bighorn Basin a world famous fossil site with well preserved specimens belonging to PETM biota. The effects of rapid climate change left it’s mark
on plants, and animals. Understanding how life reacted to sudden carbon gas emissions will help predict how our current global warming event could affect life on Earth. The famous Keeling’s Curve that started by measurements of atmospheric carbondiokside levels now makes the fact that we are pumping a lot of it in the air.

Chasing Ice – Sundance 2012 Winner from Joe DeVanon on Vimeo.

When there’s a lot of carbon dioxide in the air, it starts to dissolve in oceans causing an increase in acidity. This has serious consequences because under acidic conditions marine organisms can’t build shells using calcium and may lead to collapse of food webs in the oceans.

Our planet is warming and the evidence is overwhelming. Glacier calvings has increased in size and frequency in Greenland and in Antarctica. The mass-balance of cryosphere is dwindling.

There had been many warming periods in the Earth’s geological past. One of the recent warming episodes was during the middle of the Miocene epoch . In one of the “Plants are Cool Too!” episode (see below) we see some of the best examples of plant species from Clarkia Idaho. This fossil site has extremely well preserved specimens from the Miocene epoch and shows vegetational changes when a warming episode was followed by a cooling period.

One interesting observation from both PETM and mid-Miocene warming periods is that Legumes (bean family) thrived in many locations having subtropical conditions. What gave Legume family an advantage in warming periods? Legume trees are well known for their hydraulic re-distribution through their root network and could be a habitable island on a dry sea of desert. They have symbiotic relationship with nitrogen-fixing bacteria and perhaps high carbondiokside levels reinforce the relationship.

Science Bulletins is a production of the National Center for Science Literacy, Education, and Technology (NCSLET), part of the Department of Education at the American Museum of Natural History.


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