The impact of certain factors on the changes in atmospheric carbon dioxide (CO₂) concentrations has yet to be elucidated. In particular, the impacts of sea surface temperature (SST) on the balance of CO₂ emissions and absorption in the atmosphere and the human use of fossil fuels have not been rigorously compared. In this study, the impact of each factor was examined using multivariate analysis. Publicly available data from prominent climate research and energy-related organizations were used. Multiple linear regression analysis was performed using the annual changes in atmospheric CO₂ levels for each year as the objective variable. The SST and human emissions for each year were the explanatory factors. After 1959, the model using the SST derived from NASA best represented the annual CO₂ increase (regression coefficient B = 2.406, P < 0.0002, model R² = 0.663, P < 7e-15). However, human emissions were not a determining factor in any of the regression models. Furthermore, the atmospheric CO₂ concentration predicted, using the regression equation obtained for the SST derived from UK-HADLEY centre after 1960, showed an extremely high correlation with the actual CO₂ concentration (Pearson correlation coefficient r = 0.9995, P < 3e-92). The difference was 1.45 ppm in 2022. In conclusion, this study is the first to use multiple regression analysis to demonstrate that the independent determinant of the annual increase in atmospheric CO₂ concentration was SST, which showed strong predictive ability. However, human CO₂ emissions were irrelevant. This result indicates that atmospheric CO₂ has fluctuated as natural phenomenon, regardless of human activity.

Journals Sci Volume 6 Issue 1 10.3390/sci6010017

Comment published on 8 October 2024, see Sci 2024, 6(4), 62.

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Net Isotopic Signature of Atmospheric CO2 Sources and Sinks: No Change since the Little Ice Age

by Demetris KoutsoyiannisORCID

Department of Water Resources and Environmental Engineering, School of Civil Engineering, National Technical University of Athens, Heroon Polytechneiou 5, 157 72 Zographou, Greece

Sci 2024, 6(1), 17; https://doi.org/10.3390/sci6010017

Submission received: 19 December 2023 / Revised: 23 February 2024 / Accepted: 29 February 2024 / Published: 14 March 2024

(This article belongs to the Special Issue Feature Papers—Multidisciplinary Sciences 2023)

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Abstract

Recent studies have provided evidence, based on analyses of instrumental measurements of the last seven decades, for a unidirectional, potentially causal link between temperature as the cause and carbon dioxide concentration ([CO2]) as the effect. In the most recent study, this finding was supported by analysing the carbon cycle and showing that the natural [CO2] changes due to temperature rise are far larger (by a factor > 3) than human emissions, while the latter are no larger than 4% of the total. Here, we provide additional support for these findings by examining the signatures of the stable carbon isotopes, 12 and 13. Examining isotopic data in four important observation sites, we show that the standard metric δ13C is consistent with an input isotopic signature that is stable over the entire period of observations (>40 years), i.e., not affected by increases in human CO2 emissions. In addition, proxy data covering the period after 1500 AD also show stable behaviour. These findings confirm the major role of the biosphere in the carbon cycle and a non-discernible signature of humans.

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