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
Natural gas diesel, jet fuel and aromatic chemicals directly from natural gas via a single-loop process. In 2011, Royal Dutch Shell's per day F–T plant went into operation in Qatar. Natural gas can be "associated" (found in oil fields), or "non-associated" (isolated in natural gas fields), and is also found in coal beds (as coalbed methane). It sometimes contains a significant amount of ethane, propane, butane, and pentane—heavier hydrocarbons removed for commercial use prior to the methane being sold as a consumer fuel or chemical plant feedstock. Non-hydrocarbons such as carbon dioxide, nitrogen, helium (rarely), and hydrogen sulfide must also be removed