More recently, in the Paleocene - Eocene Thermal Maximum, about 55 million years ago, a rise of 5oC in ocean temperature (recorded in stable isotope ratios in various geological deposits) and 8oC on land occurred. (dotearth.blogs.nytimes.com)
Stable isotope ratios of carbon and nitrogen are especially popular in ecological studies. (sciencedaily.com)
No, some other animal probably converted the grass into meat on the hoof, and the hominids got the characteristic carbon stable isotope ratio from eating the grazing animal — they ate grass indirectly, at one remove. (williamcalvin.com)