Carbon dioxide of fossil fuels and deforestation have caused the atmospheric concentration of carbon dioxide to increase by about 43% since the beginning of the age of industrialization. Most carbon dioxide from human activities is released from burning coal and other fossil fuels. Other human activities, including deforestation, biomass burning, and cement production also produce carbon dioxide. Human activities emit about 29 billion tons of carbon dioxide per year, while volcanoes emit between 0.2 and 0.3 billion tons. Human activities have caused to increase above levels not seen in hundreds of thousands of years. Currently, about half of the carbon dioxide released
Carbon capture and storage (timeline) Sleipner field produces natural gas and light oil from the Heimdal sandstones, which are about 2,500 m below sea level. The natural gas produced at Sleipner contains unusually high levels (about 9%) of carbon dioxide, but the customers require less than 2.5%. To encourage companies to cut their carbon emissions, the Norwegian government imposes a carbon tax equivalent to about $50 per ton of CO released into the atmosphere. To avoid paying the tax, and as a test of alternative technology, all of the CO extracted since 1996, when gas production started at Sleipner, has been pumped back deep underground.