A global climatology of diurnal variations in sea-surface temperature based on in situ drifting-buoy data has been created. The diurnal warming signal derived from these data correlates well with estimates from a version of the Stuart-Menteth (2004) model, which parametrises the diurnal cycle based on incoming short-wave radiation, wind speed and time of day, that has been modified to accept monthly inputs. An estimate is also made of the bias in estimates of tropospheric temperature derived from the Microwave Sounding Unit instruments that is due to the drift in local equator crossing time of the satellite orbits. In the tropics, this contribution is approximately 13% of the observed trend in tropospheric temperatures.