Atmospheres, Climate, Weather

Astroclimes — Measuring The Abundance Of CO2 And CH4 In The Earth’s Atmosphere Uusing Astronomical Observations

By Keith Cowing

Status Report

astro-ph.EP

September 19, 2025

Filed under astro-ph.EP, atmosphere, biosignature, Earth, exoplanet, Greenhouse Effect, greenhouse gas

Astroclimes — Measuring The Abundance Of CO2 And CH4 In The Earth’s Atmosphere Uusing Astronomical Observations — Ground level DMFs retrieved by Astroclimes (blue) and from the CAMS global greenhouse gas reanalysis model (orange) for CO2 (top), CH4 (middle) and H2O (bottom), the latter which also shows the humidity measurements taken by the CAHA weather station (green), converted to ppm based on the measured temperature and pressure at the time of observation using equation (24). For CO2 and CH4, the Astroclimes values have been vertically shifted to match the CAMS data based on the 𝑐0 values obtained in the long-term trend fitting function described in the text. The BICs of the Astroclimes CO2 and CH4 retrievals are reported with respect to the same fits used to remove the long term trend (solid black lines) and is compared to the BICs of the Astroclimes retrievals and a horizontal line centred on their mean value (dashed gray lines). — astro-ph.EP)

Although a number of satellites and ground-based networks measure the total column volume mixing ratio (VMR) of these gases, they rely on sunlight, and column measurements at night are comparatively scarce. We present a new algorithm, Astroclimes, that hopes to complement and extend nighttime CO₂ and CH₄ column measurements.

Astroclimes can measure the abundance of GHGs on Earth by generating a model telluric transmission spectra and fitting it to the spectra of telluric standard stars in the near-infrared taken by ground-based telescopes. A Markov Chain Monte Carlo (MCMC) analysis on an extensive dataset from the CARMENES spectrograph showed that Astroclimes was able to recover the long term trend known to be present in the molecular abundances of both CO₂ and CH₄, but not their seasonal cycles.

Using the Copernicus Atmosphere Monitoring Service (CAMS) global greenhouse gas reanalysis model (EGG4) as a benchmark, we identified an overall vertical shift in our data and quantified the long term scatter in our retrievals. The scatter on a 1 hour timescale, however, is much lower, and is on par with the uncertainties on individual measurements.

Although currently the precision of the method is not in line with state of the art techniques using dedicated instrumentation, it shows promise for further development.

Marcelo Aron Fetzner Keniger, David Armstrong, Matteo Brogi, Siddharth Gandhi, Marina Lafarga

Comments: 16 pages, 13 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM); Atmospheric and Oceanic Physics (physics.ao-ph)
Cite as: arXiv:2509.10258 [astro-ph.EP] (or arXiv:2509.10258v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2509.10258
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Submission history
From: Marcelo Aron Fetzner Keniger
[v1] Fri, 12 Sep 2025 14:00:43 UTC (3,867 KB)
https://arxiv.org/abs/2509.10258
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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