Aerosols are minute particles suspended in the atmosphere. When these particles are sufficiently large, we notice their presence as they scatter and absorb sunlight.  

• Their scattering of sunlight can reduce visibility (haze) and redden sunrises and sunsets. Aerosols interact both directly and indirectly with the Earth’s radiation budget and climate. 
• As a direct effect, the aerosols scatter sunlight directly back into space. 
• As an indirect effect, aerosols in the lower atmosphere can modify the size of cloud particles, changing how the clouds reflect and absorb sunlight, thereby affecting the Earth’s energy budget  
• Aerosols come from both natural and human sources—and sometimes both at once. Dust, for example, is scoured from deserts, the dried-out edges of rivers, dry lakebeds, and more.  

• Its concentrations in the atmosphere rise and fall with climate; in cold, dry, periods in the planet ‘s history like the last ice age, more dust filled the atmosphere than during warmer stretches of Earth ‘s history. 

Source: NCERT