Carbon Sediments Reconsidered
One of the major measurements that paleoclimatologists and other scientists who try to figure out Earth's climate in the distant past rely on is the ratio of two different isotopes of carbon, 13C/12C. This ratio, also called delta 13C (δ13C), has been used to estimate the carbon content of Earth's going back more than 150 million years. Now a new study, appearing in the pages of the Proceedings of the National Academy of Sciences, has cast the accepted interpretation of δ13C into doubt.
Peter K. Stewart, in an article titled Global synchronous changes in the carbon isotopic composition of carbonate sediments unrelated to changes in the global carbon cycle, has found that “the carbon isotopic (δ13C) composition of bulk carbonate sediments deposited off the margins of four carbonate platforms/ramp systems (Bahamas, Maldives, Queensland Plateau, and Great Australian Bight) show synchronous changes over the past 0 to 10 million years. However, these variations are different from the established global pattern in the δ13C measured in the open oceans over the same time period.” For a more detailed discussion of what this ratio means and how isotopes are used to provide historical measurements called proxies, see The Resilient Earth Chapter 13, Experimental Data and Error.
What does this mean? It means that many of the readings climate scientists have been depending on to help formulate theories about how Earth's climate system works are wrong, “For example,” Stewart writes, “from 10 Ma to the present, the δ13C of open oceanic carbonate has decreased, whereas platform margin sediments analyzed here show an increase.” This doesn't invalidate the use of proxies, they are useful and often the only measurements we have. It does reinforce what we have said about historical climate data—that it is uncertain and prone to errors in both measurement and interpretation. And when you are trying to formulate a theory you cannot hope to succeed if you start with inaccurate experimental data!
Bottom line? As the author said in the paper abstract, “inferences regarding the interpretation of changes in the cycling of organic carbon derived from δ13C records should be reconsidered in light of the findings presented here.” In other words, climate theory once again needs to be corrected.