Friday, April 08, 2011

New Fossils Confirm A Very Warm Earth During the Pliocene

Mollusks that have been found in Pliocene sediments indicate that the temperature may have been between 18 and 28 degrees Fahrenheit higher than today. The Pliocene was toward the tail end of the “age of the apes” in which there were large-bodied hominoids in just about every continent on earth. It was at the end of the Miocene that the ape fossil evidence begins to disappear in non-tropical areas. Kim DeRose, of PhysOrg writes:
“Our data from the early Pliocene, when carbon dioxide levels remained close to modern levels for thousands of years, may indicate how warm the planet will eventually become if carbon dioxide levels are stabilized at the current value of 400 parts per million,” said Aradhna Tripati, a UCLA assistant professor in the department of Earth and space sciences and the department of atmospheric and oceanic sciences.
The key word in that sentence is “eventually.” Admittedly, the Pliocene is not that far back and so it is clear that the climate can change somewhat quickly. It also seems clear that the earth is going to do what the earth is going to do and there is not much we can do to change it. The temperature got that high during the Pliocene without any humans around to help it do so. It is not immediately clear that humans are going to make a whole heck of a lot of difference this time.

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  1. Thanks for the post. Very interesting article.

    I must say, however, that their data are a bit messy. The oxygen-isotope range within single molluscs and within each taxa is enough to demonstrate that several of their assumptions were potentially not valid (buffered 18O signal of the water, equilibrium fractionation, etc.). Moreover, the inconsistent 'seasonality signal' between taxa suggests there is a vital effect not accounted for.

    In any case, I am a bit troubled by the co-author's statement above. This study, granting the validity of their results, only elucidates climate in a single arctic environment, and says nothing about the global expectations for a 400-ppm-CO2 world. Without the seasonal growth of (lots of) polar sea ice, as well as continental ice sheets, the difference in albedo would be the main driver of higher temperatures—not CO2. The most rapid climate shifts have occurred because of runaway melting in continental ice sheets (e.g. younger dryas). Hence, one major concern is that rising CO2 will cause enough warming to significantly impact polar sea ice and continental ice sheet formation.

    Hope that made sense...sorry about the rant.

  2. It did. Thanks for the input.

  3. If I remember correctly, it was the younger dryas that Ryan and Pitman pounced on to explain the “Black Sea Flood,” which led to the stories of the flood that later influenced the Mesopotamians and Hebrews.