A radiative transfer postprocessor calculates microwave brightness temperatures Tb from climate experiments investigating supersonic aircraft exhaust impacts with the Global Climate/Middle Atmosphere Model (GCMAM) at the NASA Goddard Institute for Space Studies. Microwave signals from the exhaust-perturbed GCMAM atmospheres are contrasted with observed interannual variability (natural ''noise'') for 1982--1991 as measured by microwave sounding unit (MSU) channels across the lower troposphere, midtroposphere, and lower stratosphere. Exaggerated ozone and water vapor perturbations at supersonic cruise altitudes produce microwave signals easily detected against natural noise. Removal of ozone greenhouse action between 200 and 50 hPa cools all MSU channels with greatest ΔTb of -8.3 K and signal-to-observed-noise (S/N) ratios above 20 in the lower stratospheric channel. Doubling middle-atmospheric water vapor above 100 hPa cools lower stratospheric Tb values by 1.5 K while warming tropospheric channels, particularly the tropopause channel. Detectable S/N ratios of 2--4 occur over the tropics and subtropics in the lower-to-middle troposphere and lower stratosphere. Realistic ozone and water vapor perturbations are based on the High-Speed Research Program/Atmospheric Effects of Stratospheric Aircraft reports. These realistic stratospheric ozone and water vapor changes produce ΔTb signals under 0.6 K and negligible S/N ratios. The slight climatic forcings are overwhelmed by natural feedbacks of high and low cloud formation, sea ice formation, and snow coverage. Thus the modeled realistic ozone and water vapor perturbations produce small and conflicting microwave signals, undetectable against natural variability and other sources of anthropogenic climatic forcing. ¿ American Geophysical Union 1996