Conclusions  Satellite observations and model simulations of the past three decades have shown a decreasing of AOD over North America and Europe but an increasing over East and South Asia, in general in line with the anthropogenic emission change, although the variation of dust makes the EAS and SAS trends less clear  It seems the dust has an increase trends in the most recent decades over Middle East and Central Asia  Over the ocean near the continental outflow regions, AOD trends are generally consistent with that in the upwind continents, although satellite data are not necessarily consistent on the direction of changes  Under the clear-sky conditions, the changes of SW downward radiation at the surface mirror the change of AOD, e.g., brightening is associated with the decrease of AOD and dimming with the increase of AOD
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