Question

Green house effect is warming due to

(a) infra-red rays reaching earth

(b) moisture layer in atmosphere

(c) increase in temperature due to increase in carbon dioxide concentration of atmosphere

(d) ozone layer of atmosphere.

Answer 1

Option c is the correct answer. Although the concentration of water vapour is much more higher than CO₂ and other green house gase, water vapour does not absorb longer wavelength radiated from earth surface. CO₂ in atmosphere absorb longer wavelength radiated from the earth surface which is responsible for global warming.

Earth receives energy from the sunlight in the form of near IR, UV and visible light. About 26 % of the incoming solar energy is reflected and almost 19 % is absorbed by the atmosphere and clouds. The remaining portion of solar energy reaches to earth surface and absorbed by the earth surface. The absorbed solar energy by the earth is radiated from the earth surface. The radiated wavelength is much longer than the wavelength that were absorbed. Now the water vapour present in the atmosphere does not absorb this longer wavelength and allow it to pass through it while CO₂ present in the atmosphere absorb this radiated longer wavelength which increases the equilibrium temperature at earth surface and thus causes global warming.