Environmental Issues

The greenhouse effect arises when certain atmospheric gases absorb and re-radiate the infrared heat emitted from the earth's surface, warming the planet. Among these gases, carbon dioxide is the single largest contributor, accounting for roughly sixty percent of the total greenhouse effect, mainly because of the enormous volumes released by burning fossil fuels and deforestation. Methane is the next major contributor at about twenty percent, released from sources such as paddy fields, wetlands, and ruminant digestion, but it is not the largest. Chlorofluorocarbons contribute around fourteen percent and additionally damage the ozone layer, yet their share is far smaller than that of carbon dioxide. Nitrous oxide contributes only about six percent and is therefore the least among these four. As described in NCERT Class 12, Chapter 16 (Environmental Issues), the relative contributions are approximately carbon dioxide sixty percent, methane twenty percent, chlorofluorocarbons fourteen percent, and nitrous oxide six percent. Plausibility check: since the four listed percentages add up close to one hundred percent and carbon dioxide holds the largest fraction, identifying it as the dominant greenhouse gas is internally consistent.