Global change and the dark of the moon. Final report

We have considered the possibility of using earthshine to measure the reflectance properties of the earth (albedo and phase function). Measurements of earthshine carried out by Danjon in 1926--33 show that even then the average albedo could be determined with a precision of {plus_minus}0.01 and that both synoptic and seasonal variations could be observed clearly. We show that, after correction for wavelength dependence and the opposition effect in the lunar reflectance properties, Danjon`s visual albedo of 0.40 can be reconciled with the ERBE satellite Bond albedo of 0.30. We recommend a modern earthshine monitoring program (advantages include global integration, continuous coverage, ground basing, and low cost) as a complement to present and planned satellite measurements.