UPSC Prelims 2012 · Question 62 of 98
UPSC Prelims 2012 question on Carbon Dioxide Infrared Absorption
- ExamUPSC CSE
- Year2012
- PaperGeneral Studies Paper I
- SubjectEnvironment and Ecology
- TopicClimate Change
- DifficultyEasy
- TypeDirect
The increasing amount of carbon dioxide in the air is slowly raising the temperature of the atmosphere because it absorbs
Show answer
Answer: D. The infrared part of the solar radiation
Verdict
Correct Answer: The infrared part of the solar radiation
Analysis
Carbon dioxide is a greenhouse gas that traps heat by absorbing long-wave infrared radiation.
This is a major reason why increasing CO2 in the atmosphere contributes to global warming.
1. The water vapour of the air and retains its heat — Incorrect
CO2 does not warm the atmosphere by absorbing water vapour.
Water vapour itself is a greenhouse gas, but CO2 mainly acts by absorbing infrared radiation.
2. The ultraviolet part of the solar radiation — Incorrect
Ultraviolet radiation is mainly absorbed by the ozone layer in the stratosphere.
CO2 does not significantly absorb UV radiation for causing global warming.
3. All the solar radiations — Incorrect
CO2 does not absorb all solar radiation.
If it did, sunlight would not properly reach the Earth’s surface.
4. The infrared part of the solar radiation — Correct
CO2 allows much of the incoming short-wave solar radiation to pass through.
The Earth absorbs this energy and re-emits it as long-wave infrared radiation, which CO2 absorbs and re-emits, trapping heat in the atmosphere.
Extra UPSC info
* Greenhouse gases include carbon dioxide, methane, nitrous oxide, ozone and water vapour.
* The atmosphere is heated more by terrestrial radiation than by direct incoming solar radiation.
* Incoming solar radiation is mostly short-wave radiation.
* Outgoing terrestrial radiation is mainly long-wave infrared radiation.
* Methane has a higher global warming potential than CO2 per molecule, but CO2 is more significant due to its larger concentration.
* The greenhouse effect is natural, but its enhancement due to human activities causes global warming.
How to crack it
Increasing CO2 raises atmospheric temperature mainly because it absorbs outgoing infrared radiation emitted by the Earth.
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