UPSC CSE Prelims 2012
Carbon dioxide (CO₂) is a significant greenhouse gas. It absorbs the infrared (IR) radiation that is re-emitted by the Earth's surface after the surface has absorbed solar energy. This absorption of outgoing longwave radiation traps heat within the atmosphere, leading to a gradual increase in atmospheric temperature, a phenomenon known as the greenhouse effect.
Option 1 is incorrect. Carbon dioxide does not absorb water vapour. Water vapour is itself a distinct and potent greenhouse gas, contributing to the atmospheric heat budget.
Option 2 is incorrect. The ultraviolet (UV) part of solar radiation is primarily absorbed by the ozone layer (O₃) in the stratosphere, not by carbon dioxide. CO₂ has minimal absorption in the UV spectrum.
Option 3 is incorrect. Carbon dioxide does not absorb all solar radiations. It selectively absorbs radiation, primarily in specific wavelengths within the infrared spectrum. A significant portion of solar radiation, including visible light, passes through CO₂ largely unabsorbed.