Revisiting the Greenhouse Effect of Non-greenhouse Gases in the Atmospheres of Earth-like Planets

Although non-greenhouse gases can vary substantially in abundance in Earth-like atmospheres, their climatic influences remain insufficiently understood.

To investigate how such gases regulate climate, we vary the abundance of N2 as a representative non-greenhouse component in one-dimensional N₂–CO₂–H₂O model atmospheres. Beyond pressure broadening of absorption lines and Rayleigh scattering emphasized in previous studies, our results show that changes in background N₂ pressure influence climate by modifying the amount of atmospheric H₂O, producing two effects: altering the thermodynamic lapse rate (H₂O-dilute warming) and changing the radiative contribution of H₂O to the greenhouse effect (H₂O-load warming).

The resulting climate response to increasing N₂ depends on the CO₂ abundance. Under low CO₂ conditions, dilution of atmospheric H₂O leads to warming, whereas under high CO₂ conditions, increased H₂O loading also produces warming.

At sufficiently high N₂ abundances, Rayleigh scattering induces cooling, an effect further amplified by the accompanying decrease in atmospheric H₂O. Under high CO₂ conditions, however, enhanced H₂O loading increases the absorption of stellar radiation and overwhelms the contribution of Rayleigh scattering, causing the cooling response to disappear.

These results reveal multiple physical pathways through which non-greenhouse gases influence climate and provide a framework for understanding climate responses and habitability in diverse Earth-like atmospheres.

Tetsuo Taki, Hiroyuki Kurokawa, Yuka Fujii, Kosuke Aoki

Comments: 15 pages, 5 figures, accepted for publication in the Astrophysical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2605.10757 [astro-ph.EP] (or arXiv:2605.10757v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2605.10757
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Submission history
From: Tetsuo Taki
[v1] Mon, 11 May 2026 15:55:19 UTC (769 KB)
https://arxiv.org/abs/2605.10757

Astrobiology, Atmosphere,