- The MODerate resolution Imaging Spectroradiometer (MODIS) aboard the Terra and Aqua satellites has been producing an aerosol product since early 2000. These data now provide us with 8 full years of near global aerosol observations. During this period we have seen the MODIS aerosol optical depth decrease over much of the northern hemisphere, and driven by tropical biomass burning increase over much of the southern hemisphere. The short term trends are seen in both the Terra and Aqua records, and local trends are verified by trends in long-term AERONET stations. This confirmation by complementary observing systems points to a robustness in the results. The year to year variation and short term trends are highly regionally specific. We examine recent interannual variation in biomass burning in the Amazon showing how the overall increase in smoke production over the past 8 years can be reversed due to a combination of wetter conditions and changes in cultural practices. We also show how a decrease in sulfur emissions in eastern Europe can affect the aerosol optical depth both locally and at a down wind receptor site in Israel. Our experience over the past 8 years shows us the complexity of the anthropogenic influence on aerosols, and how that influence is both regionally specific and a moving target. The results make a strong argument for continued high quality monitoring of the global aerosol system from ground-based and space-based sensors.