New Study Thoroughly Disassembles The CO2-Drives-Climate Assumption In One Fell Swoop

Not only does CO2 have no discernible effect on climate, but any alleged anthropogenic role within the hypothetical greenhouse effect is not detectable either.

In recent decades there has been a concerted effort to assert it is “settled” science to characterize variability in the atmospheric CO2 concentration – assumed to be modulated by human activity – as the predominant factor in both climate change and the so-called greenhouse effect.

Science, however, is never truly settled.

A new Frontiers study succinctly unsettles this prevailing paradigm with surgeon-like precision. In under 20 pages the authors deliver a cogent critique of the CO2-drives-climate presumption. A few of the key points include:

• CO2 only contributes about 4-5% to the greenhouse effect, whereas water vapor and clouds contribute 95%.

• Of that 4-5% greenhouse effect contribution from CO2, just 4% of that can be attributed to human activities (i.e., fossil fuel emissions). Thus, about 96% of the 4% contribution from CO2 can be attributed to natural processes.

“WV [water vapor] and clouds (for which WV is responsible) dominate the ARE [atmospheric radiative effect], while CO2 contributes only 4-5% to it. Also, anthropogenic CO2 emissions are only 4% of the total, with the vast majority (96%) being natural. Additionally, evidence suggests that changes in temperature precede those in CO2 concentration, thus challenging the assumption that CO2 drives temperature.”

• As Fig. 10 in the study indicates, observed changes in the atmospheric CO2 concentration cannot be demonstrated to have exerted any effect in altering longwave radiation measurements, much less the surface temperature. A hypothetical doubling the CO2 concentration [NC-RAGs, or non-condensing radiatively active gases] “results in a temperature increase of zero”.

“[W]hile the role of CO2 in photosynthesis is important in biochemical terms, it becomes negligible in terms of its contribution to the surface energy balance.”

“[T]he observed increase of the atmospheric CO2 [from 300 ppm to 420 ppm] has not altered the ARE [atmospheric radiative effect or greenhouse effect] in any discernible way.”

Image Source: Koutsoyiannis and Tsakalias, 2025

Greenhouse Effect and Greenhouse Gases = Atmospheric Radiative Effect and Radiatively Active Gases

Common-use terms like greenhouse effect and greenhouse gases are misrepresentations of what occurs in the real-world atmosphere. Heat transfer for both a greenhouse and in the real-world surface-troposphere is dominated by convection, not radiation.

Atmospheric mass is much denser near the surface, decreasing with altitude. This leads to a 6.5°C per km temperature gradient in the troposphere.

“[H]igher atmospheric mass increases the heat capacity of the atmosphere, and thus decreases the surface net radiative cooling [and] increases the global mean surface temperature” – Chemke and Kaspi, 2017

So, for example, while the temperatures at the base of equatorial Mount Kilimanjaro range around 24°C annually, the mean summit temperatures average about -18°C. This 42°C temperature differential is similar, physics-wise, to the 36 Kelvin (K) surface warming (252 K vs. 288 K) commonly attributed to the Earth’s so-called greenhouse effect (atmospheric radiative effect), or to greenhouse gases (radiatively active gases) like CO2 and water vapor.

But just as the summit-to-base 42°C Kilimanjaro temperature differential has to do with the lapse rate/temperature gradient, and not the radiative effect of variations in the concentration of gases like CO2, so too does the 36 K temperature differential for the surface-atmosphere. Thus, CO2, a non-condensing radiatively active gas (NC-RAG), can be said to have exactly zero effect on the 252 K vs. 288 K temperature gradient.

“Hence, it is the temperature gradient that makes the surface-level temperature increase from about 252 K … to about 288 K (i.e., by 36 K). This increase is usually attributed to the ‘greenhouse effect’, but it is mainly the result of the temperature gradient.”

“The effect of the NC-RAG [non-condensing radiatively active gases] is zero for an isothermal atmosphere.”

Image Source: Koutsoyiannis and Tsakalius, 2025

The paper – including the supplementary data compilation – is notable both for its concise simplicity and its wide-ranging coverage in critiquing the “settled” significance of the CO2 impact.