The burning of coal, gas and oil is the dominant form of commercial energy production. During the 1980s, energy generation was responsible for over half of the global warming problem. In 1990, the burning of fossil fuels released about six thousand million tonnes of carbon into the atmosphere, as well as other greenhouse gases such as methane and nitrous oxide and the pollutants which generate ozone. The other major source of greenhouse gases is agriculture, forestry and related land-use activities. These account for close to a quarter of the global warming problem, releasing a range of gases including methane, nitrous oxide and carbon dioxide into the atmosphere.
Most emissions are the result of deforestation.
Changing land use represents Vietnam's main contribution to global warming. Land-use change in Vietnam released ten times as much carbon into the atmosphere as did energy production during the late 1980s. Other forms of agricultural activity also release greenhouse gases into the atmosphere. Methane, for example, is produced in the digestive systems of herbivores such as beef cattle, dairy cows, goats and sheep. It is also produced by organic decomposition in water-logged areas such as paddy fields.