How is heat lost from the surface of the Earth? What is its significance? Class 9

How is heat lost from the surface of the Earth? What is its significance? Class 9

Question 1.

How is heat lost from the surface of the Earth? What is its significance? Class 9

Answer:

(a) Re-radiation (Infrared Radiation):

1. The Earth’s surface absorbs solar radiation and re-radiates it back into the atmosphere as infrared (heat) radiation.
2. This is the primary way heat is lost from the surface.

(b) Trapping by Greenhouse Gases:

1. Greenhouse gases like CO₂, CH₄ and water vapour absorb some of this outgoing infrared radiation and prevent it from escaping into space.
2. The remaining heat escapes into outer space.

(c) Convection:

1. Warm air near the Earth’s surface rises upward, carrying heat away from the surface into the atmosphere.
2. This drives winds and weather patterns in the troposphere.

(d) Evaporation:

1. Water evaporates from oceans, rivers and lakes, absorbing heat from the surface and carrying it upward as water vapour.

Significance of Heat Loss:

1. It maintains the energy balance of the Earth — energy received from the Sun equals energy lost.
2. It drives winds, ocean currents and the water cycle.
3. Greenhouse gases trapping some outgoing heat keeps Earth warm enough for life.
4. Excess trapping due to increased CO₂ causes global warming, disrupting the climate.