Plants and other photoautotrophs use CO2 (carbon dioxide) in the process of to make and oxygen. Both plants and animals use oxygen in the biological process of and make more CO2. The is the main regulator of CO2 in the atmosphere, because it covers most of the Earth and CO2 dissolves easily in it. Millions of years ago, huge deposits of carbon were stored, which were formed from dead plants and other organisms. Today these deposits are burned as fossil fuels, which include , , and . More CO2 is released in the atmosphere today than in the past because of the . But is a greenhouse gas, as is water, and methane, and too much CO2 in the atmosphere may be responsible for human accelerated .
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