Alkanes make a significant contribution to the greenhouse effect as discussed under:
1. Combustion of alkanes release large amount of carbon(IV) oxide in the atmosphere which causes greenhouse effect.
2. Anaerobic decomposition of plants and animal remains liberates methane in the atmosphere which is also responsible for greenhouse effect.
3. Alkanes are converted to chlorofluorocarbons (CFCs) which are used as propellants in aerosols and as refrigerant gases. CFCs are very efficient greenhouse gases. CFCs contribute about 15- 20% to the greenhouse effect. Greenhouse warming effect of one molecule of a typical CFC molecule is about 1000 times that of a carbon(IV) oxide molecule