Greenhouse Effect
Human-Caused Gas Increases
Most greenhouse gases have both natural and anthropogenic (human-caused) sources, but since the beginning of the industrial revolution, human sources have dominated the observed increase in atmospheric carbon dioxide concentration.
 Click to enlarge This graph clearly shows an increase in atmospheric carbon dioxide concentration in the last 50 years. The annual oscillation in the graph is explained by a decrease in atmospheric CO2 during the vegetative growing season in the Northern hemisphere and an increase in the winter months when plants are dormant and natural and anthropogenic carbon dioxide contributions to the atmosphere continue. |
The main sources of greenhouse gases due to human activity are: | |
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Burning fossil fuels adds substantial levels of carbon dioxide to the atmosphere and industrial emissions also add chlorofluorocarbons and other gases to the atmosphere. | |
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Land use changes add carbon dioxide to the atmosphere by removing natural vegetation. Deforestation removes a carbon dioxide sink which means more stored carbon from the soil goes into the atmosphere. | |
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Livestock digestion and manure add methane to the atmosphere. | |
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Rice farming adds methane to the atmosphere. | |
