The vertical structures of recent decadal-scale trends of temperature and humidity over the tropical western Pacific Ocean are documented using daily data at 16 pressure levels (from the surface to 300 mbar) from the four radiosonde stations. Both temperature and specific humidity have increased throughout the troposphere since the mid-1970's The specific humidity increase is sufficiently large that relative humidity also shows positive trends at all tropospheric levels above the surface despite the warming trend. The specific humidity trend is greatest near the surface and decreases with height, whereas the temperature trend increases with height above the boundary layer. Specific humidity in the tropics is shown to be a sensitive indicator of long-term climate change, because the vertical structure of the specific humidity trend (largest near the surface) is distinctly different from the vertical structure of the seasonal cycle or interannual variability of specific humidity variability, which exhibit peak amplitudes in mid-troposphere. Thus short-term climate variability of humidity is a poor proxy for long-term climate change. Reproduction of the difference in vertical structures of long-term and short-term specific humidity fluctuations would provide a good test of the fidelity of model projections of climate change. ¿ American Geophysical Union 1992