Hothouse Earth ...

66 million years of Earth's climate uncovered from ocean sediments 

Credit: Thomas Westerhold / Adam Kutz

A hothouse earth is coming, predicted by the IPCC with the distinct possibility of temperatures rising 9-14 degrees Celsius by 2300, levels last seen 66-50 million years ago in the mid Eocene known as the Paleocene Eocene Thermal Maximum. Comforting is it not?

"The IPCC projections for 2300 in the 'business-as-usual' scenario will potentially bring global temperature to a level the planet has not seen in 50 million years," Zachos said.

The new global climate record CENOGRID (lower panel) is the first to continually and accurately trace how Earth's climate has changed since the great extinction of the dinosaurs 66 million years ago. The record was generated using the oxygen (shown) and carbon isotopes from tiny microfossils found in deep-sea sediments collected by the IODP ship R/V JOIDES Resolution (shown in the photo) and shows the natural range of climate change and variability over the last 66 million years. 

Critical to compiling the new climate record was getting high-quality sediment cores from deep ocean basins through the international Ocean Drilling Program (ODP, later the Integrated Ocean Drilling Program, IODP, succeeded in 2013 by the International Ocean Discovery Program). Signatures of past climates are recorded in the shells of microscopic plankton (called foraminifera) preserved in the seafloor sediments. After analyzing the sediment cores, researchers then had to develop an "astrochronology" by matching the climate variations recorded in sediment layers with variations in Earth's orbit (known as Milankovitch cycles).

Now that they have compiled a continuous, astronomically dated climate record of the past 66 million years, the researchers can see that the climate's response to orbital variations depends on factors such as greenhouse gas levels and the extent of polar ice sheets.

"In an extreme greenhouse world with no ice, there won't be any feedbacks involving the ice sheets, and that changes the dynamics of the climate," Zachos explained.

It may be worse if the American Geophysical Union's findings are correct.

Earth may be 140 years away from reaching carbon levels not seen in 56 million years

Date:

February 20, 2019

Source:

American Geophysical Union

Summary:

Total human carbon dioxide emissions could match those of Earth's last major greenhouse warming event in fewer than five generations, new research finds. A new study finds humans are pumping carbon dioxide into the atmosphere at a rate nine to 10 times higher than the greenhouse gas was emitted during the Paleocene-Eocene Thermal Maximum (PETM), a global warming event that occurred roughly 56 million years ago.

We did this to ourselves.