Rafael Muñoz-Carpena, Ph. D. Professor, Agricultural and Biological Engineering Department, WI Faculty Fellow
Thursday, January 16 at 3:00pm in the Reitz Union Auditorium
Title: A Peep into Environmental Complexity and Resilience? Global Sensitivity and Uncertainty Evaluation of Mathematical Models
Abstract: Concern about catastrophic tipping points has motivated inquiry to better understand ecosystem dynamics in the presence of human action. This requires that we confront multiple challenges in the evaluation of complex systems. One challenge is that resilience has proven difficult to quantify; another issue is that the value of model complexity relative to system complexity is disputed; and finally, local methods for assessing uncertainty are inadequate for more complex models. Modelers often face a difficult trilemma relating model complexity, sensitivity, and uncertainty that can ultimately compromise the relevance of the model for a particular problem. We address these challenges simultaneously by proposing a means of evaluating ecological resilience via comparative global sensitivity and uncertainty analysis (GSA/UA) of models of varying complexity. We suggest that output probability distribution functions from GSA/UA permits quantification of ecological resilience in terms of the probability of whether a system will remain in a pre-existing state or shift to a different state. We outline the methods for using global sensitivity and uncertainty analysis to evaluate ecological resilience and provide examples from recent research used to assess ecosystem management options. The conceptual and methodological framework is proposed as an indispensable component in the complex systems model development and evaluation process.
Ellen E. Martin, Ph. D. Professor, Department of Geological Sciences, FCI Faculty Fellow
Title: From the Greenhouse to the Icehouse: Climate Change 33 Million Years Ago
Abstract: During greenhouse conditions in the early Cenozoic (65-33 million years ago) Antarctica was a green continent with beech trees and conifers. These conditions ended rapidly with the development of the Antarctic ice sheet ~33 million years ago, marking the transition to an icehouse world. This talk will use paleoceanographic data to evaluate theories that this dramatic climate transition was caused by development of a cold ocean current around Antarctica and/or changes in the global carbon cycle.
