An 8-year record of global-mean infrared emission from the surface-atmosphere system, as measured by instruments on the Nimbus 7 satellite, shows an interesting downward trend with time. While it is tempting to attribute this trend to increasing atmospheric CO2 and other greenhouse gases, the present study demonstrates that such a greenhouse gas radiative signal is well below the level of instrument detectability. It is shown instead that the temporal variability of the Nimbus 7 infrared measurements is strongly correlated with observed variability of global-mean surface air temperature, so that the Nimbus 7 measurements actually provide an independent means of appraising global climate variability. Although the last two decades have, on average, been a period of global warming, embedded within this is a period of global cooling that is a significant cause of the downward temporal trend in the Nimbus 7 emission measurements. ¿ American Geophysical Union 1990