Publication Date:
2019
Description:
〈span〉〈div〉Abstract〈/div〉Reducing the uncertainty in predictions of future climate change is one of today’s greatest scientific challenges, with many significant problems unsolved, including the relationship between 〈span〉p〈/span〉CO〈sub〉2〈/sub〉 and global temperature. To better constrain these forecasts, it is meaningful to study past time intervals of global warmth, such as the Eocene (56.0–33.9 Ma), serving as climatic analogues for the future. Here we reconstructed 〈span〉p〈/span〉CO〈sub〉2〈/sub〉 using the stomatal densities of a large fossil Lauraceae (laurel) leaf database from ten sites across the Eocene of Australia and New Zealand. We show that mostly moderate 〈span〉p〈/span〉CO〈sub〉2〈/sub〉 levels of ∼450–600 ppm prevailed throughout the Eocene, levels that are considerably lower than the 〈span〉p〈/span〉CO〈sub〉2〈/sub〉 forcing currently needed to recreate Eocene temperatures in climate models. Our data record significantly lower 〈span〉p〈/span〉CO〈sub〉2〈/sub〉 than inferred from marine isotopes, but concur with previously published Northern Hemisphere Eocene stomatal proxy 〈span〉p〈/span〉CO〈sub〉2〈/sub〉. We argue that the now globally consistent stomatal proxy 〈span〉p〈/span〉CO〈sub〉2〈/sub〉 record for the Eocene is robust and that climate sensitivity was elevated and/or that additional climate forcings operated more powerfully than previously assumed.〈/span〉
Print ISSN:
0091-7613
Electronic ISSN:
1943-2682
Topics:
Geosciences
