Carbon footprint man-made infrastructures resulted in a net loss to the atmosphere, -0.6 Mg C ha y. Carbon dioxide emissions into the atmosphere, and the emissions of other GHGs, are often associated with the burning of fossil fuels, like natural gas, crude oil and coal. While this is harmful to the environment, carbon offsets can be purchased in an attempt to make up for these harmful effects. The Kyoto Protocol defines legally binding targets and timetables for cutting the GHG emissions of industrialized countries that ratified the Kyoto Protocol. Accordingly, from an economic or market perspective, one has to distinguish between a
Carbon in the Earth's atmosphere (approximately 810 gigatonnes of carbon) and dissolved in all water bodies (approximately 36,000 gigatonnes of carbon). Around 1,900 gigatonnes of carbon are present in the biosphere. Hydrocarbons (such as coal, petroleum, and natural gas) contain carbon as well. Coal "reserves" (not "resources") amount to around 900 gigatonnes with perhaps 18,000 Gt of resources. Oil reserves are around 150 gigatonnes. Proven sources of natural gas are about (containing about 105 gigatonnes of carbon), but studies estimate another of "unconventional" deposits such as shale gas, representing about 540 gigatonnes of carbon. Carbon is also found in methane hydrates