There are three main gases that contribute to the global warming, carbon dioxide and methane and nitrous oxide.
Carbon dioxide comes from burning fossil fuels such as oil, coal and natural gas. It might come from various ways, but mainly from power plants and transportation emissions. The statistics from the United Nations have shown that 80 to 85 percent of the carbon dioxide that is emitted to the atmosphere comes from the use of fossil fuel. Since the first industrial revolution, the carbon dioxide has increased dramatically.
Methane is another important gas contributing to the global warming. It is produced from organism decaying in a low oxide enviroment. The main sources of the meethane in the atmosphere came from wetlands and marshlands. Human activities also contribute a large number of methane emission. Every year,rice cultivation produces 100Tg, cattle and sheep ranching produces 100－150Tg. There will be a net increase of methane by 350Tg every year.
From the EPA website,nitrous oxide comes from "Primary human-related sources of N2O are agricultural soil management, animal manure management, sewage treatment, mobile and stationary combustion of fossil fuel, adipic acid production, and nitric acid production." Even though 90 percent of it will be photolyzed from sun radiation.
