The increase in the concentration of atmospheric greenhouse gases ( like water vapour, carbon dioxide (CO2), methane and ozone) is the main cause of rise in the atmospheric temperature. Greenhouse gases in the atmosphere acts like a mirror and reflect back the heat radiations. The greenhouse gases like carbon dioxide in the atmosphere is generated mainly from burning of fossil fuels (oil, gas, petrol, kerosene, etc.). So, we can say that global warming is caused by greenhouse effect.