Plants and other photoautotrophs use CO2 (carbon dioxide) in the process of photosynthesis to make sugar and oxygen. Both plants and animals use oxygen in the biological process of respiration and make CO2. The ocean 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 decayed organisms. Today these carbon rich deposits are burned as fossil fuels, which include oil, natural gas, and coal. 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 and other greenhouse gases produced by human activities in the atmosphere may be responsible for human accelerated greenhouse effect.
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