Although the radiative transfer in a one-dimensional atmosphere is well understood, this is not true of transport in higher dimensional bodies and research in radiative transfer applied to more realistic atmospheric structures has been a topic of much research over the past decade. Significant recent theoretical contributions applied to the Earth's atmosphere are found in the work of Evans [1993a] and Gabriel et al. [1993], and in the Monte Carlo modelling of O'Brien [1992], Barker [1992] and Cahalan et al. [1994a and b] among others. These studies reinforce the understanding learned from earlier research highlighting the complexities introduced by spatial variability on the radiative transfer. The basic conclusion from these studies is that when radiative properties are averaged over some volume of atmosphere composed of clouds, say, then this average depends on how the cloudy material is distributed within it in a crucial way. The problem is that this dependence is large and the challenge is to identify the most meaningful way of relating the spatial variation to radiative transfer. Like the problem of continuum absorption, spatial effects on radiative properties permeates almost all research in atmospheric radiation, particularly as it applies to both modelling and to the remote sensing of clouds. Studies like these demonstrate how spatial structure can dominate over potential microphysical effects that may otherwise alter the albedo of clouds, for example---the latter being a topic of some interest to climate change as discussed below.