Here is a graph showing the Hitran absorption curve for the atmosphere. Absorption includes both downdwelling and upwelling power. Temperature here is the standard atmosphere curve. Curves for both current molecular concentrations and for current with a doubling of CO2. At this scale, there's no way to distinguish between the 2xco2 and current graphs. Values are power per Km per m^2.
While not visible on the graph, the downdwelling energy is actually distributed across the atm depth fairly regularly. Almost all of the absorption on the upwelling occurs well within 1km, with about 20W/m^2 occuring within the first 4 meters (12 feet).
(edited to correct change in image addr)