Transient middle Eocene atmospheric C[O.sub.2] and temperature variations

The long-term warmth of the Eocene (~56 to 34 million years ago) is commonly associated with elevated partial pressure of atmospheric carbon dioxide (pC[O.sub.2]). However, a direct relationship between the two has not been established for short-term climate perturbations. We reconstructed changes in both pC[O.sub.2] and temperature over an episode of transient global warming called the Middle Eocene Climatic Optimum (MECO; ~40 million years ago). Organic molecular paleothermometry indicates a warming of southwest Pacific sea surface temperatures (SSTs) by 3[degrees] to 6[degrees]C. Reconstructions of pC[O.sub.2] indicate a concomitant increase by a factor of 2 to 3. The marked consistency between SST and pC[O.sub.2] trends during the MECO suggests that elevated pC[O.sub.2] played a major rote in global warming during the MECO. 10.1126/science.1193654