The Tod Spieker Colloquium

Emergent Constraints on Terrestrial Carbon-Climate Feedbacks presented by David Schimel, Research Scientist, Jet Propulsion Laboratory, California Institute of Technology

Monday, January 27, 2014
3:00 PM
Bunche Hall, Room 1261

Click here to download the announcement.

Feedbacks from the terrestrial carbon cycle will mitigate or exacerbate future climate change, but are poorly constrained by observations. We review key global carbon and ecosystems data and discuss strategies for using these to reduce model uncertainty.   The global magnitude of the emergent sensitivity parameter beta—the atmospheric CO2 concentration dependence of terrestrial carbon uptake—has been particularly difficult to constrain with experiments and observations.  Theory and experiments predict that CO2 fertilization should be scaled to plant productivity, with a maximum in the tropics.  The CO2 fertilization hypothesis appears to be contradicted by analyses of atmospheric CO2 that suggest high uptake in mid-latitudes. Here we show local and global evidence for tropical sinks supporting a long-hypothesized negative terrestrial feedback to CO2 and climate.  Integration of atmospheric, in situ and simulation analyses show a significant tropical uptake not associated with forest regrowth or other disturbance processes.  We estimate a present-day tropical CO2 fertilization effect of 1.3 ± 0.6 Pg C y-1, suggesting that beta is a significant negative feedback globally, and dominates current terrestrial feedbacks.

2014 Colloquium Schedule 

February 10th
Gregory Simon
Assistant Professor,  Department of Geography and Environmental Sciences
University of Colorado, Denver

February 24th
Fernando Riosmeña
Assistant Professor of Geography and Institute of Behavioral Science
University of Colorado at Boulder

March 10th
Erika Marin-Spiotta
Assistant Professor,  Department of Geography
University of Wisconsin- Madison

April 21st
George Hurtt
Professor and Research Director
Department of Geographical Sciences
University of Maryland

April 28th
Deborah Martin
Associate Professor of Geography and Associate Director
Graduate School of Geography
Clark University

May 19
Laura Pulido
Professor of Ethnicity and American Studies
University of Southern California