According to a new research, models used to estimate past ocean temperatures might have been based on flawed assumptions, which, if true, could mean that our ancient seas were far cooler than previously determined and current warming is even greater than we thought. The study, published in Nature Communications, involved a team of climate scientists from French and Swiss universities who reviewed the chemical process that has served as a proxy for estimating ocean temperatures from millions of years in the past. By looking at the ratio of oxygen-18 to oxygen-16 in the calcite of the exoskeletons of tiny marine organisms called foraminifera, which varies with the isotope concentrations in the environment and the water's temperature and is used to determine the differences in the oxygen isotopes in fossils, a record of the temperature when they lived over 100 million years ago can be estimated. The researchers, however, have found evidence that suggests the ratio of oxygen-18 to oxygen-16 in the buried marine life might not be quite as stable as initially thought, and may indicate that today's rapid global warming trend is even more dramatic that current models indicate. To find out more check out Burial-induced oxygen-isotope re-equilibration of fossil foraminifera explains ocean paleotemperature paradoxes.