This paper aims to establish the required precision for column-integrated CO2 concentration data to be useful in constraining surface sources. We use the method of synthesis inversion and compare the uncertainties in regional sources calculated from a moderate-sized surface network and either global or oceanic coverage of column-integrated pseudodata. With a simple measure of total uncertainty, we require precision of monthly averaged column data better than 2.5 ppmv on a 8¿¿10¿ footprint for comparable performance with the existing surface network. If coverage is only oceanic we require 1.5 ppmv precision. We recommend more detailed studies on the feasibility of obtaining such observations from current and future satellite instruments. ¿ 2001 American Geophysical Union