A method of lowering the temperature of the Earth comprises placing particles of sand into the upper atmosphere, wherein the particles are selected on the basis of size and refractive index such that the particles will scatter and reflect incoming sunlight having a wavelength in the near-IR back into space. The average diameter of the particles may be selected based on the index of refraction and the Mie scattering intensity for dielectric particles, to maximize the amount of light scattered at wavelengths between 0.8 μm and 2 μm. The average diameter of the particles may be selected based on the index of refraction and the Mie scattering intensity for dielectric particles, to minimize the amount of light scattered at wavelengths between 5 μm and 20 μm.
