SHS Events Publication

Inaugural Lecture - Chronis Tzedakis

Start: Nov 15, 2011 06:30 PM
End: Nov 15, 2011 08:00 PM

Location: Gustave Tuck Lecture Theatre

15 November 2011

UCL Wilkins Gustave Tuck Lecture Theatre - 6.30pm

Professor Chronis Tzedakis (Geography)

Chronis Tzedakis was a Research Associate in Plant Sciences, Cambridge, a NERC Advanced Fellow in Geography and a Fellow of Robinson College, Cambridge, a Senior Lecturer and Professor of Global Change Palaeoecology in the School of Geography, University of Leeds.  He joined UCL as Professor of Physical Geography in 2009.  His research centres on understanding the response of vegetation to variations in climatic forcing on orbital and millennial/centennial timescales.  Since 2008, he has been leading an international collaborative network on ‘Past Interglacials’ (PIGS).

The natural length of the current interglacial

Although no glacial inception is projected to occur at current anthropogenically-driven CO2 concentrations of 390 ppmv, considerable uncertainty remains over the natural length of the present interglacial in the absence of human interference. 

The notion that our current interglacial, already 11.6 thousand years old, would be drawing to a close has been based on the observation that the duration of recent past interglacials was approximately 11 thousand years.  However, uncertainty over an imminent hypothetical glaciation arises from the unusually subdued present minimum in summer solar radiation. 

While a reduction in summer solar radiation is the primary trigger for glacial inception, lower CO2 concentrations can also lead to glaciation.  Modelling experiments, however, indicate that pre-industrial CO2 levels of 280 ppmv were not sufficiently low to lead to new ice growth. 

Chronis Tzedakis argues that an alternative approach is to use empirical evidence from intervals characterized by similar radiative signature to the current interglacial to gain insights into the timing of the next hypothetical ‘natural’ glacial inception.  Examination of an interglacial period ~780 thousand years ago suggests that the current interglacial would be nearing its end, provided that CO2 concentrations were 250-240ppmv.

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