Net primary production (NPP) of terrestrial vegetation is probably the most fundamental measure of global habitability. Previous attempts to estimate NPP of large areas have developed correlations with one of three basic variables; actual evapotranspiration (AET), leaf area index (LAI), or absorbed photosynthetically active radiation (APAR). This paper presents ideas that integrate these three variables into a new formula for estimating NPP of large areas. The three key variables needed, LAI, intercepted shortwave radiation (Qint), and surface temperature (Tgrow) are all measurable by current satellites. Consequently, a first dynamic estimate of global terrestrial NPP may now be possible integrating satellite measurements with simple ecosystem models of carbon conversion efficiency.