The analysis of one year of CERES{Terra data provides further evidence that the longwave radiation escaping from the atmosphere exhibits signi cant variability according to the azimuthal angle of observation. A regional analysis of this variability shows that the anisotropy in azimuth is maximum over mountain and desert areas and under cloud{free conditions. A relative di erence between North and South views of about 5% in annual average is observed over the Himalayan region in the 8 ð€€€ 14 m infrared window. We think that the remote sensing community should be aware of this variability, in particular when analyzing infrared data provided by instruments on geostationary orbits. Indeed, in this case, the azimuthal anisotropy may lead to systematic overestimation of the outgoing longwave radiation and to biases on retrieved quantities such as the surface temperature.