Since its 2003 launch, ICESat (Ice, Cloud, and land Elevation Satellite) has been providing global lidar observations of ice sheet elevation. However, the accuracy of this laser altimetry is affected by the presence of clouds. Forward scattering by cloud particles increases the photon path length, thus making the surface appear farther from the satellite. This is known as “atmospheric range delay”. The range delay is a function of cloud height, optical depth, particle size and shape, and the lidar telescope field of view (FOV). Using observed cloud property statistics over Greenland and Antarctic ice sheets from analyses of ICESat and CALIPSO data as input, we show that atmospheric range delay varies significantly with the telescope FOV. For the ICESat telescope FOV (375 µrad corresponding to 225 m on the ground), the range delay is at the decimeter level under certain conditions, while the accuracy requirement of the mission is at the centimeter level. Our results imply that in order to meet the surface altimetry accuracy goal for the future ICESat-II mission, a reduction of the telescope FOV is required.