Greenhouse gases are the ingredients of the atmosphere that add to the greenhouse effect. Some greenhouse gases are present naturally in the atmosphere, whereas few green house gases a consequence of human activity. The greenhouse gases that are present in the atmosphere naturally include water vapor, carbon dioxide, nitrous oxide, methane and ozone. There are a few human activities, which increase the levels of most of these naturally occurring gases. The concentration of various green house effect gases has substantially increased in the recent times.

Greenhouse gases, which are the major cause of global warming, trap heat in the earth's atmosphere. Since the middle of the 19th century, human agriculture and industrialization have dispensed an enormous quantity of these green house gases into the atmosphere, where these have trapped enough heat to begin climate change. According to the United Nations, there has been a rise of about 0.6 degrees Celsius during the past century. More warming is expected to occur in the coming decades

The main reasons for the emission of gases that are a cause of green house effect are burning of fossil fuel like coal in the power plants for the purpose of generation of electricity. Fossil fuel burning leads to high emissions of carbon dioxide gas. Another green house gas is methane. Methane is more than 20 times as effectual as CO2 at entrapping heat in the atmosphere.

Methane is obtained from resources such as rice paddies, bovine flatulence, bacteria in bogs and fossil fuel manufacture. Almost in all parts of the world, rice is grown on flooded fields. When fields are flooded, anaerobic situation build up and the organic matter in the soil decays, releasing methane to the atmosphere. Nitrous oxide, which is a colorless gas with a sweet odor, is also a green house gas. The main sources of nitrous oxide include nylon and nitric acid production, cars with catalytic converters, the use of fertilizers in agriculture and the burning of organic matter. A greater emission of nitrous oxides in the recent decades is leading global warming. Another jump in the category of green house gases is in the name of hydroflourocarbons and perflourocarbons, man made chemicals initiated as a substitute to other chemicals that deplete the atmosphere's protective ozone layer.

The speedy increase in greenhouse gases over the past century is a matter of worry in at least 800,000 years, according to a study of the oldest Antarctic ice core. Scientists at the British Antarctic Survey (BAS) in Cambridge have established the fact that there have been eight cycles of atmospheric alterations in the past 800,000 years when green house gases like carbon dioxide and methane have risen to high levels. Each time, the earth also had a comparatively high temperatures linked with warm; inter glacial periods, which were most certainly associated with levels of carbon dioxide and probably methane in the atmosphere. However, present levels of green house gases are much higher than everything seen during those previous warm periods.

Although much is being done to reduce the emission of these green house gases, but the efforts are still not enough. An international agreement called the Kyoto Protocol has been made among the various nations to cut down the emission of these gases. There is a dire need that each one understands the ill effects of these green house gases and does the need full.