Global climate change has resulted primarily from the accumulation of carbon dioxide (CO2) and other greenhouse gases
(GHGs) in the atmosphere over the last 150 years. However, recent studies indicate that, on average, 40 per cent of the potential warming by GHGs is being masked by certain aerosols (and aerosol-cloud interactions) that increase the reflection of sunlight.

Current day concentrations of ground level ozone (O3) are commonly reducing crop yields by between 5 and 35 % at agriculturally important locations across South Asia. O3 induced economic crop losses could be in the region of $4 billion per annum for staple crops in South Asia; such losses are likely to impact more on poor and vulnerable people.

Petrochemicals are hydrocarbons, obtained from naturally occurring raw materials viz. petroleum, natural gas, coal etc. Coal was initially the basic raw material for organic chemical industry. However the basic feedstock has changed recently from coal to petroleum. This is attributed to the recent innovation and technological advance in the field of chemical industry based on petroleum feedstock.