Greenhouse gases trap heat and thus make the Earth warmer.
Many greenhouse gases occur naturally, such as water vapour, carbon dioxide, methane, nitrous oxide, and ozone.
Others such as chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6) result exclusively from human industrial processes.
How do Human Activities contribute to the Greenhouse Gases?
Human activities also add significantly to the level of naturally occurring greenhouse gases:
- Carbon dioxide is released into the atmosphere by the burning of solid waste, wood and wood products, and fossil fuels (oil, natural gas, and coal).
- Nitrous oxide emissions occur during various agricultural and industrial processes, and when solid waste or fossil fuels are burned.
- Methane is emitted when organic waste decomposes, whether in landfills or in connection with livestock farming. Methane emissions also occur during the production and transport of fossil fuels.
You can read more on find out at these links:
http://environment.about.com/od/faqglobalwarming/f/greengases.htm
