From Watts Up With That?
In his paper, “Relative Importance of Carbon Dioxide and Water in the Greenhouse Effect: Does the Tail Wag the Dog?”, Demetris Koutsoyiannis explores the greenhouse effect’s primary drivers, positing that water vapor and clouds vastly overshadow carbon dioxide (CO₂) in terms of their contribution. Using a radiative transfer model (MODTRAN), Koutsoyiannis analyzes downwelling and outgoing longwave radiation and derives macroscopic relationships that express greenhouse gas effects quantitatively. His calculations suggest that water vapor and clouds contribute between 87% to 95% of the greenhouse effect, while CO₂’s impact is only around 4% to 5%. The findings also indicate that recent increases in atmospheric CO₂, from 300 to 420 ppm, contribute negligibly—an effect quantified at just 0.5% for both downwelling and outgoing radiation.
Abstract
Using a detailed atmospheric radiative transfer model, we derive macroscopic relationships of downwelling and outgoing longwave radiation which enable determining the partial derivatives thereof with respect to the explanatory variables that represent the greenhouse gases. We validate these macroscopic relationships using empirical formulae based on downwelling radiation data, commonly used in hydrology, and satellite data for the outgoing radiation. We use the relationships and their partial derivatives to infer the relative importance of carbon dioxide and water vapour in the greenhouse effect.
The results show that the contribution of the former is 4% – 5%, while water and clouds dominate with a contribution of 87% – 95%. The minor effect of carbon dioxide is confirmed by the small, non-discernible effect of the recent escalation of atmospheric CO₂ concentration from 300 to 420 ppm. This effect is quantified at 0.5% for both downwelling and outgoing radiation.
Water and clouds also perform other important functions in climate, such as regulating heat storage and albedo, as well as cooling the Earth’s surface through latent heat transfer, contributing 50%. By confirming the major role of water on climate, these results suggest that hydrology should have a more prominent and more active role in climate research.
Keywords: Greenhouse effect; longwave radiation; water vapour; carbon dioxide; evaporation radiative forcing
Submitted 2024-09-22, Accepted 2024-10-28. https://doi.org/10.53234/scc202411/01
A good rule of thumb to keep in mind is that anything that calls itself ‘science’ probably isn’t.
J.R. Searle (1984)
The paper positions these findings in opposition to the widely held view that CO₂ is the critical driver of Earth’s greenhouse effect. Koutsoyiannis argues that water’s abundance and rapid hydrological cycling allow it to dominate atmospheric temperature regulation, effectively acting as the primary greenhouse gas. He claims that the historical focus on CO₂ has skewed climate research, diminishing hydrology’s role and limiting a complete understanding of climate dynamics.
Koutsoyiannis also critiques the mainstream climate science perspective, which he suggests has become too intertwined with political agendas. He points to discussions in prominent journals that frame CO₂ as the “control knob” of climate, a narrative he finds unsupported by empirical evidence. By applying his model, he challenges the assertion that removing CO₂ would dramatically alter Earth’s climate; instead, he contends that water vapor would continue to regulate temperature through its dominant greenhouse effect and short atmospheric residence time.
The study incorporates data from ERA5 Reanalysis and satellite-based radiation measurements, specifically the CERES project, for validation. These datasets provide insight into radiation profiles and support the author’s argument that water vapor’s regional variability and rapid cycling enable it to exert a powerful greenhouse effect that CO₂ cannot match.
However, Koutsoyiannis acknowledges that the hypothetical removal of CO₂, often discussed in theoretical studies, lacks empirical backing, as CO₂ has consistently been a part of Earth’s atmosphere over geological timescales. He also contrasts the rapid turnover of water vapor with CO₂’s longer residence time, highlighting the latter’s well-mixed nature across the atmosphere as a potential reason why its warming effects appear diffused.
Through his analysis, Koutsoyiannis calls for a reorientation of climate research, urging the scientific community to afford greater attention to hydrology and to reconsider CO₂’s central role in climate models. He concludes that the understanding of Earth’s climate may be limited by the current emphasis on CO₂ emissions, which he argues overlooks the nuanced and regionally specific effects of water vapor.
In sum, “Does the Tail Wag the Dog?” is a critique of prevailing climate science paradigms, advocating for a model that recognizes water vapor and clouds as the foremost greenhouse agents while downplaying CO₂’s overall effect. Koutsoyiannis’s paper encourages a shift in climate research focus toward hydrology and questions the mainstream positioning of CO₂ as the cornerstone of climate change theory.
In addition, Koutsoyiannis has posted reviewers comments from his earlier attempts to publish in other journals.
This file is the Supplementary Information of the paper “Relative importance of carbon dioxide and water in the greenhouse effect: Does the tail wag the dog?” It contains interesting material as it demonstrates the current practices of silencing voices that disagree with mainstream opinions, which are purported to be science. The contained materials include the rejection files from three journals, namely Hydrological Sciences Journal, MDPI Hydrology and Ecohydrology and Engineering. The document contains all reviews and replies to them, as well as key exchanges with the journal’s Editorial Offices. Replies to reviews are contained in the case that the Editor accepted the request to rebut them—otherwise no replies were prepared. [See the paper at:
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