🌱 Environment & EcologyUPSC 2012Sustainable Development

The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere, because it absorbs

aThe water vapour of the air retains its heat.
bThe ultraviolet part of the solar radiation.
cAll the solar radiations.
dThe infrared part of the solar radiation.
✓ Correct answer: d) The infrared part of the solar radiation.
ExplanationGreenhouse Effect is a naturally occurring phenomenon that warms and covers the lower atmosphere of the planet, keep- ing it at a temperature where life may survive.The earth’s cooling and warming are balanced by them.Without this, the current 15 degrees Celsius average temperature of the earth’s surface would be -19 degrees Celsius.Human-induced greenhouse gas emissions upset the natural balance & lead to increased warmth.Option (d) is correct: Carbon dioxide absorbs the infrared (IR) radiation emitted by the Earth’s surface.When sunlight reaches the Earth it warms the surface, which then re-emits this energy as infrared radiation.CO₂ molecules absorb this IR radi- ation, trapping heat in the atmosphere and causing the tempera- ture to rise.The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere because it ab- sorbs the infrared part of the solar radiation.It absorbs energy with a wavelength of 15 μm (micrometres).111

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