Now aerosols are also originated from human activities, mainly burning of fossil fuels and industrial emissions. Artificial aerosols represent around 10 per cent of global aerosol emissions, while dust aerosols represent more than 50 per cent.
There is much to study about aerosol impacts on regional and global climate. For now, it is very difficult to analyse the increase or decrease of aerosol emissions. It is also a case study to determine if aerosols are warming or cooling the overall global temperature.
The radiative effect of aerosols tends to cause the cooling of the ground beneath them. Because the radiative effect of aerosols reflects sunlight back into space, the direct cooling effect is the consequence of the reduction of solar radiation reaching the ground.
Aerosols, depending on their composition and density could also have a warming effect as they absorb solar radiation in infrared wave lengths.
Aerosols have an indirect effect too, they constitute the nuclei condensation, crucial for cloud formation. In fact, water vapour needs floating particles in order to condensate and start the formation of water droplets which will form clouds.