Question

How much sunlight gets lost through the atmosphere?

Answer 1

About 45% when you consider both what is reflected and absorbed by the atmosphere and by clouds.

Explanation:

The Earth energy budget (balance between the Earth and the Sun) usually shows an average 6% of solar energy is reflected by the atmosphere, and 20% is reflected by clouds (clouds being opaque and white are quite reflective comparatively). The amount absorbed by the atmosphere is 16% on average (primarily UV radiation absorbed by ozone), and the amount absorbed by clouds is about 3%. Total is 45%, but you may or may not want to include clouds when you ask this question.

http://okfirst.mesonet.org/train/meteorology/EnergyBudget.html