Barometric pressure and total ozone conten may significantly depart from their mean climatology values; these values, however, are used when processing the visible remote sensing (VRS) data with the aim of estimating the phytoplanktonic pigments concentration (chlorophyll a+phaeophytin a, in milligrams per cubic meter) within the upper ocean. The effect of ignoring such departures upon the retrieved concentration has been simulated for the broad ocean range (0.015--20 mg/m3). The simulation is effected for typical VRS situations (geometry, aerosol) when information about the variable aerosol is not available when entering the processing (as is the case with the Coastal Zone Color Scanner (CZCS) data) or, conversely, when such information has been separately obtained (simulation of future sensors with dedicated near-IR channels). The result is that in both these cases the use of mean climatology values leads to variable misestimates of the pigment content, by a factor of up to 2 in many common VRS situations, and above 2 for very low or high actual pigment content. After the results are discussed, the conclusion is that the actual values of the barometric pressure and of the ozone content will have to be introduced in the processing of future visible sensor data in order to preserve the expected accuracy. With regard to the exploitation of the CZCS archive, this requirement is not so essential, insofar as the pressure and ozone effects on the pigment concentration retrieval remain of the same order as the noise due to the limited radiometric accuracy of this sensor. However, at the scale of a CZCS scene, neglecting the strong structures in the pressure and ozone content fields may bias the phytoplankton concentration mapping. The use of the actual values is therefore recommended. ¿ American Geophysical Union 1989