A greenhouse gases are gases in earth’s atmosphere that absorbs and emits radiant energy, causing the greenhouse effect, which is warming of the planet. These gases trap heat from the sun and prevent the heat from escaping back into space, thus these gases leads to an increase in earth’s average temperature.

Without greenhouse gases, the temperature of earth would have been -18 degree celcius on average, rather than present average of 15 degree celcius.

Primary greenhouse gases in earth’s atmosphere are:
Water Vapour, Carbon Dioxide, Methane, Nitrous Oxide, and ozone.

The causes of Global Warming:

Man-made Causes of Global Warming:

1. Burning Fossil Fuels:
   The burning of coal, natural gases for production of energy, transportation, and industrial processes which leads to release of large amounts of carbon dioxide into the atmosphere.

2. Deforestation:
   The number of trees reduces due to clearing forests for agriculture, logging, and urbanization, and hence less carbon dioxide is consumed for photosynthesis. This results in higher atmospheric CO2 levels.

3. Industrial Processes:
   Industrial activities or processes release large amount of greenhouse gases like carbon dioxide, methane, and nitrous oxide.

4. Transportation Vehicles:
   The use of vehicles results in various gaseous emissions. Vehicles burn fossil fuels which emits a large amount of carbon dioxide and other toxins into the atmosphere.

5. Chlorofluorocarbon: With the excessive use of air conditioners and refrigerators, humans have been adding CFCs into the environment which affects the atmospheric ozone layer, causing ozone layer depletion.

6. Overpopulation:
   Increase in population means more people breathing and releasing carbon dioxide. This leads to an increase in the level of carbon dioxide in the atmosphere.

   Natural Causes of global warming:
   

   1. Volcanoes :
   Volcanoes are one of the largest natural contributors to global warming due to the ash and smoke emitted during volcanic eruptions.

   2. Water Vapour:
   Due to the increase in the earth’s temperature, more water gets evaporated from the water bodies and stays in the atmosphere.

   3. Forest blazes:
   Forest blazes or forest fires emit a large amount of carbon-containing smoke. These gases are released into the atmosphere and increase the earth’s temperature resulting in global warming.