Carbon (chemical element C) is one of the most abundant elements in the universe.
All known life forms are carbon-based and it amounts to about 18% of a human body.
Carbon dioxide (CO2) and methane (CH4) make up about 0.04% of our atmosphere by volume.
However, alongside water vapour, nitrous oxide and ozone (collectively called greenhouse gases) they help to keep our planet warm.
In fact, without these gases, the Earth’s surface would be about 18 °C below zero – far too cold for nearly all life to survive. Greenhouse gases occur naturally, but human activities have directly increased the amount of carbon dioxide, methane and some other gases in our atmosphere. There is overwhelming evidence that this has enhanced the natural greenhouse effect, contributing to the warming we have seen over the last century or so. For more information on this visit our in depth climate section
When studying our climate, scientists draw their evidence from many sources. It is important that they look at all the processes that influence our climate, and one of the most important is the carbon cycle.
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