Intercomparison of observed cloud radiative forcing - A zonal and global perspective

Cloud radiative forcing determined by the Earth Radiation Budget Experiment (ERBE) scene identification method and two regression methods is compared using identical data sources and the same analysis periods. Results confirm that from the global perspective the increased reflection of SW radiation induced by clouds is greater than outgoing longwave energy trapped by clouds. The estimates of net effect obtained from the three methods are found to be in good agreement (within 3.5 W/sq m). It is concluded that differences in published global mean values of net cloud radiative forcing are mainly due to different data sources and analysis periods. The best estimated annual mean among all previous estimates is considered to be the ERBE measurement (-17.3 W/sq m).