Rapid atmospheric CO(2) changes associated with the 8,200-years-B.P. cooling event

By applying the inverse relation between numbers of leaf stomata and atmospheric CO(2) concentration, stomatal frequency analysis of fossil birch leaves from lake deposits in Denmark reveals a century-scale CO(2) change during the prominent Holocene cooling event that occurred in the North Atlantic region between 8,400 and 8,100 years B.P. In contrast to conventional CO(2) reconstructions based on ice cores from Antarctica, quantification of the stomatal frequency signal corroborates a distinctive temperature–CO(2) correlation. Results indicate a global CO(2) decline of ≈25 ppm by volume over ≈300 years. This reduction is in harmony with observed and modeled lowering of North Atlantic sea-surface temperatures associated with a short-term weakening of thermohaline circulation.