Climatic ups and downs in a disturbed Jurassic world

The tropical, warm, and equable climate of the Jurassic world is regularly challenged by geoscientists, especially since oxygen isotopes (delta O-18) of fossil hardparts have been used to reconstruct the paleotemperature history of seawater. By applying the innovative "SiZer" (significant zero crossings of the derivatives) statistical approach to a newly compiled delta O-18 database for the Jurassic, we demonstrate the occurrence of major and multiscale delta O-18 changes mainly related to climate disturbances. For the first time, two long-term anomalies in delta O-18 are identified during the Toarcian and the Late Jurassic, in conjunction with intensive volcanism in large igneous provinces. These results support a strong influence of repeated volcanic pulses on the modulation of pCO(2), temperatures, and polar ice cap volumes over protracted periods. At shorter time scales, 13 relatively rapid (0.5-1 m.y.) and significant warming and cooling events are identified, the causes of which include transient fluctuations in greenhouse gas concentrations related to still-debated mechanisms.