Untangling the Threads

摘要

During the last deglaciation, between approximately 18,000 and 10,000 years ago, the atmospheric concentration of CO_2 rose from around 180 to more than 260 parts per million. Although several plausible explanations for this increase have been proposed, it has not yet been possible to assign one over the others definitively. Lourantou et al. provide an additional constraint for the competing scenarios: a record of the isotopic composition of the carbon in atmospheric CO_2 over the time interval in question. Because different sources of atmospheric CO_2 have distinct carbon isotopic compositions, the authors could determine where in the carbon system the CO_2 was coming from by comparing their data with proxy records related to carbon cycle processes, and also by conducting simulations using carbon cycle box models.