Assessing the Efficacy of Stratospheric Forcing Agent

Tuesday, 16 December 2014
Robert W Portmann, NOAA Earth System Research Lab, Boulder, CO, United States
The radiative forcing and climate response of stratospheric radiatively active species are analyzed with a focus on stratospheric water vapor, ozone, and aerosol. While all of these agents can act as forcing or feedbacks, they are analyzed here using a forcing/response framework. We estimate perturbations of these species using observations (stratospheric ozone and aerosol) and using modeled changes in carbon dioxide increase experiments using a climate model (stratospheric water vapor). We use the Community Earth System Model (CESM) throughout. The radiative forcing and climate responses are estimated using consistent model calculations (fixed sea surface temperature and slab ocean configurations of the model). Thus, we are estimating the efficacy of these forcing agents. The results suggest that some stratospheric forcing agents have less impact on surface climate than there radiative forcing would indicate. Since the perturbation used for stratospheric water is obtained by its change in carbon dioxide change experiments, the results have direct implications to the climate feedback strength of stratospheric water vapor.