Abstract:

A direct measurement from space of the impact of increased atmospheric CO2 on the spectra of Earth’s infrared radiation is presented. The goal of this study is to experimentally confirm that the direct effects of CO2 growth on the Earth’s outgoing infrared spectra follow theoretical estimates, by developing a methodology that allows for a direct and more precise comparison between theory and observations. In this methodology, a search is performed to find selected ensembles of observed atmospheric vertical profiles of temperature and water vapor that are as similar as possible. By analysing the spectral radiances measured from space by the Atmospheric Infrared Sounder (AIRS), corresponding to the selected ensembles of profiles, the effects of increased CO2 on the spectra can be isolated from the temperature and water vapor effects. The results illustrate the impact of the increase of CO2 on the infrared spectra and compare well with theoretical estimates. This is the first time that the spectral signature of the increase of CO2 (isolated from temperature and water vapor changes) has been directly observed from space. As such, these results confirm a critical foundation of the science of global warming.