# Use the polynomial expression in the back of the book to estimate Cvig/R at 200 K as a reference.

Use the polynomial expression in the back of the book to estimate Cvig/R at 200 K as a reference..

CO2 is given a lot of credit for global warming because it has vibrational frequencies in the infrared (IR) region that can absorb radiation reflected from the Earth and degrade it into thermal energy. The vibration at  /k = 290K (903cm–1) is particularly important.

(a) Plot Cvig/R versus T for CO2 in the range 200–400 K. Use the polynomial expression in the back of the book to estimate Cvig/R at 200 K as a reference. Also plot the polynomial expression on the same chart as a dashed line.

(b) Use your Internet search skills to learn the wavelength range of the IR spectrum. How many wavelengths are there? What fraction does the wavelength at 903cm–1 comprise? If the Earth’s atmosphere was composed entirely of CO2, what fraction of IR energy could be absorbed by CO2?

(c) The Earth’s atmosphere is really 380ppm CO2. If the absorption efficiency is proportional to the concentration, how much IR energy could be absorbed by CO2 in this case? Use the polynomial expression in the back of the book to estimate Cvig/R at 200 K as a reference.

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