Radiative Heating Due to Increased CO2: The Role of H2O Continuum Absorption in the 12–18 μm Region

Abstract

In the 12–18 μm spectral region, the CO₂ bands are overlapped by the H₂O pure rotational band and the H₂O continuum band. The 12–18 μm H₂O continuum absorption is neglected in most studies concerned with the climatic effects of increased CO₂. In this study, we examine the role of H₂O–CO₂ overlap in detail. Specifically, the effect of the water vapor continuum in the 12–18 μm region on the radiative heating due to increased CO₂ is investigated. It is found that although the longwave surface radiative heating due to increased CO₂ is considerably reduced at low latitudes by H₂O continuum absorption, where water vapor partial pressures are high, the radiative heating of the surface/troposphere system as a whole is minimally altered.