Carbon dioxide in Earth's atmosphere atmosphere, oceans, soil, rocks, and volcanism. Both carbon cycles are intrinsically interconnected and atmospheric gaseous carbon dioxide facilitates the carbon cycle. Natural sources of atmospheric carbon dioxide include volcanic outgassing, the combustion of organic matter, wildfires and the respiration processes of living aerobic organisms. Man-made sources of carbon dioxide include the burning of fossil fuels for heating, power generation and transport, as well as some industrial processes such as cement making. It is also produced by various microorganisms from fermentation and cellular respiration. Plants, algae and cyanobacteria convert carbon dioxide to carbohydrates by a process called photosynthesis. They gain the
Coal dioxide, a greenhouse gas that causes climate change and global warming. Coal is the largest contributor to the human-made increase of CO in the atmosphere, 40% of the total. In 2016 world gross carbon dioxide emissions from coal usage were 14.5 giga tonnes. For every megawatt-hour generated, coal-fired electric power generation emits around a tonne of carbon dioxide, which is double the approximately 500 kg of carbon dioxide released by a natural gas-fired electric plant. In 2013, the head of the UN climate agency advised that most of the world's coal reserves should be left in the ground to avoid