Carbon dioxide in Earth's atmosphere Atmospheric O levels are decreasing in Earth's atmosphere as it reacts with the carbon in fossil fuels to form . Burning fossil fuels such as coal, petroleum, and natural gas is the leading cause of increased anthropogenic ; deforestation is the second major cause. In 2010, 9.14 gigatonnes of carbon (GtC, equivalent to 33.5 gigatonnes of or about 4.3 ppm in Earth's atmosphere) were released from fossil fuels and cement production worldwide, compared to 6.15 GtC in 1990. In addition, land use change contributed 0.87 GtC in 2010, compared to 1.45 GtC in 1990. In 1997, human-caused Indonesian peat fires
Underground coal gasification upstream processes), resulting in a large decrease in greenhouse gas (GHG) emissions. UCG product gas can also be used for: In addition, carbon dioxide produced as a by-product of underground coal gasification may be re-directed and used for enhanced oil recovery. Underground product gas is an alternative to natural gas and potentially offers cost savings by eliminating mining, transport, and solid waste. The expected cost savings could increase given higher coal prices driven by emissions trading, taxes, and other emissions reduction policies, e.g. the Australian Government's proposed Carbon Pollution Reduction Scheme. Cougar Energy and Linc Energy conducted pilot projects in