How is heat lost from the surface of the Earth? What is its significance?
Heat is lost from the Earth's surface when it absorbs incoming solar radiation and re-radiates it in the infrared region.
While some of this heat escapes into space, greenhouse gases like CO₂, CH₄, and water vapour absorb a portion of it, preventing it from entirely leaving the atmosphere.
The significance of this process is that it maintains Earth's temperature. Without the atmosphere trapping this outgoing heat, the Earth would be too cold for life to survive. However, excess greenhouse gases can cause global warming.
Explanation
The textbook context states that the Earth's surface absorbs sunlight and re-radiates heat in the infrared region. This is the mechanism by which heat is lost. The significance lies in the atmosphere's role: greenhouse gases trap this outgoing heat, preventing it from all escaping into space. Without this trapping, the Earth would be too cold for life. However, an excess of CO₂ from human activities enhances this greenhouse effect, causing global warming.