Greenhouse gases generated from human activity absorb infrared radiation from Earth and keep it from being dispersed outside our atmosphere. This is a major cause of global warming. Compare the path length required to absorb 90.% of the Earth’s radiation near a wavelength of 7 μm for CH₃CCl₃[ε (λ ) = 1.8 (cm atm)^-1 ] and the chlorofluorocarbon CFC-14[ε (λ ) = 4.1 × 10³ (cm atm)⁻¹] assuming that each of these gases has a partial pressure of 1.5 × 10⁻⁶ atm.