The question of how the internal climate dynamical state will interact with climate change is of great theoretical and practical importance. This study explores the disconcerting possibility that the response of the climate system to a radiative perturbation of a given magnitude may depend strongly upon the climate state itself. The underlying process, referred to here as feedback drift, has been documented in one coupled ocean-atmosphere model, a state-of-the-art, full physics climate model. This work is an effort to understand the physical mechanism underlying this feedback drift using both empirical studies and simplified, explanatory models, in order to assess the possibility that such feedback drift might occur in other fully resolved climate models, and to develop the necessary empirical understanding and diagnostic techniques to determine whether such a process might be occurring in nature.
If indeed climate feedback drifts significantly with respect to the underlying climate dynamical state, our understanding of climate change thresholds, the perception of supposed "safe" levels of anthropogenic greenhouse gasses, and our understanding of the overall role of climate variability in the climate system will necessarily be altered. Thus, while exploratory, this research is potentially of great practical importance.
This project will contribute to the training of a Ph.D. student in the area of cloud/climate interactions. The work will help quantify a potential risk factor in future climate change that is of intrinsic interest to decision makers responsible for implementing emission scenarios that "target" a given level of climate change.
