Others believe that different factors are responsible for the recorded temperature changes. You could say there is a heated debate over the issue. The composition of air. The most common greenhouse gas is carbon dioxide. There are several sources of carbon dioxide, including combustion of fossil fuels and the burning of the rainforests.
Human respiration is also a source of carbon dioxide.
In order to convert the foods we eat into the energy required to sustain life, oxygen is used to metabolize glucose, a simple sugar.