New ACP Letter: Direct observational evidence from space of the effect of CO₂ increase on longwave spectral radiances: the unique role of high-spectral-resolution measurements

31 May 2024

This paper presents direct evidence from space (solely based on observations) that CO₂ increase leads to the theoretically expected effects on longwave spectral radiances. This is achieved by using a methodology that allows us to isolate the CO₂ effects from the temperature and water vapor effects. By searching for ensembles of temperature and water vapor profiles that are similar to each other but have different values of CO₂, it is possible to estimate the direct effects of CO₂ on the spectra.

Executive editor's statement: The core element of climate change is the sensitivity of the Earth's climate system to the balance between incoming solar radiation and outgoing terrestrial radiation at the top of the atmosphere. CO₂ is one of the key atmospheric parameters controlling the outgoing longwave radiation. In this paper, hyper-spectral satellite data of the outgoing long wave radiation from a decade of observations are successfully used for the first time to disentangle the radiative effect of CO₂ increase from those of other relevant parameters such as temperature and water vapour variations. The paper demonstrates convincingly that the observed radiative changes agree excellently with theoretical predictions of outgoing long wave radiation changes due to the observed CO₂ increase. While solely based on observations from space, these results confirm a fundamental theoretical underpinning of the science of global warming.

Contact: João Teixeira (teixeira@jpl.nasa.gov)