To increase effectiveness of measurements of concentration of greenhouse gases questions on optimum accounting of non-certainty of results of measurements of low gases concentrations at the ground distributed nets of atmospheric measurements are considered. It is noted that temporal and structural non-stability of atmospheric aerosol leads to occurrence of non-certainty of carried out measurements. It is suggested to use the method of non-conditional variation optimization to determine the optimum interrelation between cost functions of researched atmospheric gas and aerosol which provides best metrological support for carried out measurements. In order to form the functional of optimization the newly suggested method of double averaging is used. The matter of suggested method of double averaging is that two following different averaging operations should be carried out sequentially: geometrical weighted averaging and algebraic averaging. To form the target functional of optimization the limitation condition should be adopted which is imposed to searched for optimum function. Solution of the formulated optimization task of non-conditional variation optimization does show that upon presence of linear interrelation between scalar cost functions of gas and aerosol the target functional could reach its maximum that is the uttermost value of non-certainty of measurements results are reached. On the base of aforesaid the heuristically recommendations on necessity to form the inverse interrelation between scalar values of cost functions of researched gas and atmospheric aerosol are formulated.