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

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Conclusions

The results of the analyses in this paper provide negative answers to the research questions posed in the Introduction. Specifically:

• From modern instrumental carbon isotopic data of the last 40 years, no signs of human (fossil fuel) CO₂ emissions can be discerned;
• Proxy data since the Little Ice Age suggest that the modern period of instrumental data does not differ, in terms of the net isotopic signature of atmospheric CO₂ sources and sinks, from earlier centuries.

Combined with earlier studies, namely [2,3,4,5,31], these findings allow for the following line of thought to be formulated, which contrasts the dominant climate narrative, on the basis that different lines of thought are beneficial for the progress of science, even though they are not welcomed by those with political agendas promoting the narratives (whose representatives declare that they “own the science”, as can be seen in the motto in the beginning of the paper).

• It the 16th century, Earth entered a cool climatic period, known as the Little Ice Age, which ended at the beginning of the 19th century;
• Immediately after, a warming period began, which has lasted until now. The causes of the warming must be analogous to those that resulted in the Medieval Warm Period around 1000 AD, the Roman Climate Optimum around the first centuries BC and AD, the Minoan Climate Optimum at around 1500 BC, and other warming periods throughout the Holocene;
• As a result of the recent warming, and as explained in [5], the biosphere has expanded and become more productive, leading to increased CO₂ concentration in the atmosphere and greening of the Earth [17,18,19,32];
• As a result of the increased CO₂ concentration, the isotopic signature δ¹³C in the atmosphere has decreased;
• The greenhouse effect on the Earth remained stable in the last century, as it is dominated by the water vapour in the atmosphere [31];
• Human CO₂ emissions have played a minor role in the recent climatic evolution, which is hardly discernible in observational data and unnecessary to invoke in modelling the observed behaviours, including the change in the isotopic signature δ¹³C in the atmosphere.

Overall, the findings in this paper confirm the major role of the biosphere in the carbon cycle (and through this in climate) and a non-discernible signature of humans.

One may associate the findings of the paper with several questions related to international policies. Do these results refute the hypothesis that CO₂ emissions contribute to global warming through the greenhouse effect? Do these findings, by suggesting a minimal human impact on the isotopic composition of atmospheric carbon, contradict the need to reduce CO₂ emissions? Are human carbon emissions independent from other forms of pollution, such as emissions of fine particles and nitrogen oxides, which can have harmful effects on human health and the environment? These questions are not posed at all in the paper and certainly are not studied in it. Therefore, they cannot be answered on a scientific basis within the paper’s confined scope but require further research. The reader may feel free to study such questions and provide sensible replies. It is relevant to note that a reviewer implied these questions and suggested negative replies to each of them.