Quantifying the Dependence of Satellite Cloud Retrievals on Instrument Uncertainty

Abstract

loud response to Earth?s changing climate is one of the largest sources of uncertainty among Global Climate Model (GCM) projections. Two of the largest sources of uncertainty are the spread in Equilibrium Climate Sensitivity (ECS) and uncertainty in radiative forcing due to uncertainty in the aerosol indirect effect. Satellite instruments with sufficient absolute accuracy and on-orbit stability to detect climate change-scale trends in cloud properties will improve confidence in our understanding of the relationship between observed climate change and cloud property trends, thus providing information to better constrain ECS and radiative forcing. This study applies a climate change uncertainty framework to quantify the impact of measurement uncertainty on trend detection times for cloud fraction, effective temperature, optical thickness, and water cloud effective radius. Although GCMs generally agree that the total cloud feedback is positive, disagreement remains on its magnitude. With the climate uncertainty framework, we demonstrate how stringent measurement uncertainty requirements for reflected solar and infrared satellite measurements enable improved constraint of SW and LW cloud feedbacks and the ECS by significantly reducing trend uncertainties for cloud fraction, optical thickness, and effective temperature. We also demonstrate improved constraint on uncertainty in the aerosol indirect effect by reducing water cloud effective radius trend uncertainty.