Agenda

Speaker: Prof. Yair Rosenthal, Rutgers University

Zoom Link: https://unive.zoom.us/j/86908436332?pwd=a2psS25HQWNSbEFwWDI2RjY5RVRNZz09

Abstract:
The pre-industrial Holocene is unique among past interglacials due to a modest, but notable increase in atmospheric CO2 and methane (CH4) during the latter half of the period despite an expected decrease given orbital parameters. Although the causes for this increase, anthropogenic or natural are debated, all climate models simulate an increase in global mean temperature in response to the increase in the greenhouse gases. Yet, many proxy reconstructions, interpreted to reflect the mean annual temperatures, indicate peak temperatures in the first half of the Holocene, arguably exceeding modern mean annual temperatures followed by cooling through the preindustrial period. This significant model-data discrepancy, known as the Holocene temperature conundrum, and the debate on the cause of the CO2 increase has undermined confidence in proxy reconstructions and climate models.  In this talk I’ll offer new perspectives on both issues.

Our recent studies have suggested that global reconstructions of the Holocene and last interglacial (LIG) periods reflect the evolution of seasonal rather than mean annual temperatures.  To overcome this bias, we have developed a Seasonal to Annual mean Transformation (SAT) method. Using this transformation, we demonstrate that in contrast with previous reconstructions, global mean annual temperatures have been increasing since the early Holocene, first in response to retreating ice sheets (12 to 6.5 thousand years ago), then due to rising greenhouse gas concentrations (0.25 ± 0.21°C over the last ~6.5 thousand years). The SAT has been challenged as a robust solution to this problem. In this presentation, we will discuss the method, its implications to global climate during the Holocene and other interglacials, and address some of the common critiques of the method, as well as provide an outlook on future development of SAT.

Bio Sketch:
Yair Rosenthal is Distinguished Professor at Rutgers, the State University of New Jersey, Departments of Marine Sciences and Earth and Planetary Sciences. He is a recognized leader in the Integrated Ocean Drilling Program and, because of this contribution to the Earth Sciences, has been nominated Fellow of the American Geophysical Union (AGU). The overarching motivation for his research is to document the history of, and understand mechanisms of climate change. Throughout his career, Yair has endeavored to develop new geochemical proxies that offer quantitative information of past ocean properties and thus the possibility for rigorous paleoceanographic reconstructions in a similar manner to that conducted with modern data.