Thursday 03 Jul 2014: CliMathNet seminar: Thermodynamic limits of the Earth system
Alex Kleidon - Max-Planck-Institut fuer Biogeochemie
The Earth’s climate system is highly complex, with interactions and feedbacks playing key roles in shaping the climatic state and its response to change. But what sets the limits to the strength of Earth system processes? In this talk, I use the laws of thermodynamics as a fundamental basis to derive the limit on how much work can be derived from the planetary radiative forcing to drive the dynamics of the Earth system. Applied to a simple box model of the surface-atmosphere system, this limit yields the magnitude of convective heat fluxes in the system, and thereby provides a constraint to the surface energy balance as well as the intensity of convective mass exchange and hydrologic cycling. Despite the simplicity of the model, this approach predicts a range of climatic characteristics across a range of scales surprisingly well, from the local energy partitioning measured at eddy covariance sites to the sensitivity of the global hydrologic cycle to surface warming. These results imply that Earth system processes appear to operate close to their thermodynamic limit, so that their magnitudes as well as their sensitivities can be robustly predicted. I close with a brief discussion of the implications of this approach and potential future work.