the radiative forcings of contrails Improving the present understanding of the optical prop- and contrail cirrus, it is necessary to erties of contrails and contrail cirrus and enhancing the improve our knowledge about their fundamental optical and radiative global satellite detection and retrieval of these clouds will properties. This study, based on two greatly benefit the evaluation of the radiative impact of subject-specific white papers (Ou aviation-induced cloudiness on climate change. and Liou 2008; Yang et al. 2008) for the Aviation Climate Change Research Initiative undertaken by