Abstract The cooling of the stratosphere in response to increasing CO2 concentration has long been recognized as a ``fingerprint'' of human effects on climate. However, the radiative mechanisms that control this cooling, particularly its magnitude and vertical structure, remain unclear. Using idealized models of spectroscopy and radiative transfer, we demonstrate that the sensitivity of stratospheric temperature to CO2 concentration is mainly driven by the distribution of mass absorption coefficients in the primary CO2 band and modulated by the emission of water vapor and ozone in other parts of the spectrum. These spectral mechanisms explain why the stratosphere cools more aloft than it does below, why each doubling of CO2 yields roughly zero to eight Kelvin of cooling across the depth of the stratosphere, and why stratospheric cooling increases the radiative forcing of CO2 by about 75%.
Cohen et al. (Thu,) studied this question.