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The greenhouse effect currently lifts Earth's surface temperature by about 23 degrees Celsius. What would our world be like without it?
AWell below freezing on average
BWarmer but much drier overall
CAbout the same as it is today
DHot enough to boil the oceans
Answer & Solution
Correct answer: A. Well below freezing on average
1. Sunlight warms the ground, which then radiates the energy back as infrared.
2. Carbon dioxide, methane and water vapor absorb that infrared and slow its escape.
3. The surface must warm until the energy leaving matches the energy arriving.
4. That blanketing raises the average surface temperature by about 23 degrees Celsius.
5. Strip the blanket away and the average falls well below freezing.
6. Earth would then be locked in a global ice age rather than merely drier.
7. Leaving the temperature unchanged would mean the blanket did nothing, which contradicts the 23 degree lift.
8. Boiling the oceans needs far more heating, not the removal of heating.
_Source: OpenStax Astronomy (CC BY 4.0), section 8.4 Life, Chemical Evolution, and Climate Change_
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