The Terra and Aqua missions will help quantify aerosol radiative forcing of climate by providing innovative measurements of the aerosol daily spatial distribution and identifying dust, smoke and regional pollution. However, these measurements are acquired at specific times of the day To what extent can such measurements represent the daily average aerosol forcing of climate? We answer this question using 7 years of dat from the AERONET of 50-70 global ground-based instruments. AERONET measures the aerosol spectral optical thickness and total precipitable water every 15 minutes throughout the day. With a data set of 1/2 million measurements, AERONET demonstrates that Terra and Aqua aerosol measurements can represent the annual average value within 2% error. This excellent Terra representation of the daily average optical thickness is independent of the particle size or range of the optical thickness.