= Solution
The size parameter $x=2\pi r/\lambda$, <complex refractive index> and particle shape determine scattering strength and direction. In the small-sphere <Rayleigh scattering> regime, <scattering cross-section> scales as $r^6\lambda^{-4}|(m^2-1)/(m^2+2)|^2$; the <Mie scattering> regime is needed when particle size approaches the <wavelength>. Particle <number density> and <particle size distribution>, <aerosol hygroscopicity> and the angular fraction returned to space control an ensemble's radiative effect. High scattering does not imply strong cooling if most light is scattered forward or the particle also absorbs strongly; <single-scattering albedo> distinguishes scattering from absorption.
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