Conclusion: Reconstructing and Modelling Past Oceans Paleoceanography of the Late Cenozoic (Elsevier) Volume 1: Methods in Late Cenozoic Paleoceanography

The science of reconstructing past climates has evolved rapidly over the past three decades. Having started as a subdiscipline of geology and geochemistry [Imbrie and Imbrie, 1979], it is today an interdisciplinary research field which unifies a large international scientific community. Some of the most innovative and suprising research in this field has important implications for future climate change. As such, paleoscience is today recognized as being of great relevance to societal concerns. For example, ice core analyzes revealed that greenhouse gas levels are higher today than they have been for hundreds of thousands of years. In other words, anthropogenic impacts are pushing the climate system towards a state for which there is no “reference climate” in paleo records of the Quaternary. Therefore a better understanding of the climate system and feedbacks within the climate system is crucial for our future. Another disconcerting finding of paleoresearch is the fact that the climate system is highly non-linear: in the past, rapid and large amplitude climate change has occured in response to slowly varying, small amplitude forcing. It is critical that policy makers understand what paleoscience has to say about rapid climate change in order to fully understand the significance of future rapid climate change. The UN-sanctioned Intergovernmental Panel on Climate Change (IPCC) recognizes the importance of understanding past climate change to predict future climate scenarios and has devoted an entire chapter in the fourth assessment report (AR4) to paleoclimates. The ocean’s high heat capacity and its ability to transport energy and to sequester and release greenhouse gases give it an important role in helping to determine the state of the planet’s climate. Compared to the atmosphere, the ocean has a long response time to perturbations and this makes it a key player in climate change on timescales of hundreds to ten thousands of years. Thus, paleoceanography is a crucial component of paleoclimatic research.