New Study: Human CO2 Emissions Responsible For 1.57% Of Global Temperature Change Since 1750

“The remaining 98.43% of climate forcing arises from sources other than anthropogenic CO2.” – Davis, 2025

When it comes to climate forcing, “atmospheric CO2 plays a minor and diminishing role in forcing contemporary global warming.”

Key quotes from Davis, 2025

“As a result of today’s higher concentrations of CO2 in the atmosphere, the radiative forcing power of CO2 has dropped to less than one-third of the forcing power in 1750.”

“The forcing attributable to atmospheric CO2 is so small relative to the Earth’s energy budget that 80% of heat captured by CO2 is reflected back into space by aerosols.”

“If the concentration of CO2 in Earth’s atmosphere continues to increase exponentially as it has since contemporary measurements began 67 years ago (see below), then the incremental contribution of CO2 forcing to global warming will continue to decline exponentially because the forcing power of CO2 wanes with higher CO2 concentrations owing to the aforementioned diminishing returns in marginal forcing.”

“These contributions of CO2 to temperature forcing must be evaluated against the above demonstration that 6.27% of RFCO2 [radiative forcing from CO2] between 1750 and 2020 is attributable to anthropogenic CO2 (Figure 1) while the remaining 93.73% is natural in origin. It follows that even if contemporary global warming were 100% attributable to increases in the atmospheric concentration of CO2 instead of the estimated 25%, 6.27% of this forcing would be attributable to human-sourced emissions of CO2. Using the more refined empirical estimates of CO2 contributions developed above, where approximately one-fourth of total forcing is attributable to atmospheric CO2, the maximum contribution of human-sourced CO2 to contemporary global warming is estimated quantitatively from empirical data as 6.27% (the computed contribution of anthropogenic CO2 forcing from 1750 to 2020, above) of 25% (the approximate mean empirical estimate of CO2 forcing of temperature, above), or 1.57% of total temperature forcing.”

Other conclusions from the study:

The full concentration of CO2 (420 ppm) currently provides only 0.0058% of the Earth’s surface energy, which is imperceptible.

There is a negative correlation (r = -0.19) between CO2 and temperature (i.e., CO2 rises as temperature falls, or temperature rises as CO2 falls) over the last 425 million years.

Image Source: Davis, 202