  There are many indications that anthropogenic global warming poses a serious
threat to our civilization and its ecological support systems. Ideally this
problem will be overcome by reducing greenhouse gas emissions. Various
space-based methods, including large-scale solar shades, diffusers or
atmospheric pollutants, have been considered to reduce the solar constant
(input flux) and the warming in case emissions reductions are not achieved in a
timely way. Here it is pointed out that proposed technologies for near-Earth
orbiting comet deflection, suggest a different kind of space-based solar shade.
This shade would be made up of micron-sized dust particles derived from comet
fragments or lunar mining, and positioned in orbits near the triangular
Lagrange points of the Earth-Moon system. Solar radiation pressure can render
such orbits unstable, but a class of nearly resonant, and long-lived orbits is
shown to exist, though the phase space volume of such orbits depends on dust
grain size. Advantages and disadvantages of this scheme relative to others are
considered.
