In summary, this regulating process has kept the Earth's global average temperature essentially constant over time. Some scientists suggest that this phenomena is proof for the Gaia hypothesis . Carbon is stored in the lithosphere in both inorganic and organic forms. Inorganic deposits of carbon in the lithosphere include fossil fuels like coal , oil , and natural gas , oil shale , and carbonate based sedimentary deposits like limestone . Organic forms of carbon in the lithosphere include litter , organic matter , and humic substances found in soils.
Some carbon dioxide is released from the interior of the lithosphere by volcanoes .
Carbon dioxide released by volcanoes enters the lower lithosphere when carbon-rich sediments and sedimentary rocks are subducted and partially melted beneath tectonic boundary zones. Since the Industrial Revolution , humans have greatly increased the quantity of carbon dioxide found in the Earth's atmosphere and oceans. Scientists estimate that future atmospheric levels of carbon dioxide could reach an amount between 450 to 600 PPM by the year 2100. The major sources of this gas due to human activities include fossil fuel combustion and the modification of natural plant cover found in grassland, woodland, and forested ecosystems. Researchers have shown that natural ecosystems can store between 20 to 100 times more carbon dioxide than agricultural land-use types.