And indeed, Svante Arrhenius supported the idea that changes in atmospheric carbon dioxide concentration are the cause of the changes in temperature. Arrhenius (
Citation1896) stated:
Conversations with my friend and colleague Professor Högbom […] led me to make a preliminary estimate of the probable effect of a variation of the atmospheric carbonic acid on the temperature of the earth. As this estimation led to the belief that one might in this way probably find an explanation for temperature variations of 5–10 °C, I worked out the calculation more in detail and lay it now before the public and the critics. (p. 267)
However, recent studies, based on palaeoclimatic and modern instrumental data, have questioned Arrhenius’s hypothesis and suggested that the causality relationship between temperature and CO2 could be opposite to this hypothesis, i.e. temperature variation could be the cause and variation in CO2 concentration could be the effect. A convincing explanation about why, in the long run, change in temperature leads and change in CO₂ concentration follows has been given by Roe (
Citation2006), who demonstrated that in the Quaternary it is the effect of Milanković cycles (Milanković
Citation1935,
Citation1941,
Citation1998) rather than of atmospheric CO₂ concentration that explains the glaciation process. Specifically, he found that variations in atmospheric CO₂ appear to lag the rate of change of global ice volume. This implies only a secondary role for CO₂ – variations in which produce a weaker radiative forcing than the orbitally‐induced changes in summertime insolation – in driving changes in global ice volume. (Roe
Citation2006; see also Koutsoyiannis
Citation2019, Koutsoyiannis and Kundzewicz
Citation2020; and references therein). (p. 1)
As for the recent changes, Koutsoyiannis
et al. (
Citation2022a,
Citation2022b,
Citation2023b) developed a stochastic methodology for detecting potential causal links and, using modern instrumental data of temperature and CO₂ concentration for the last 65 years, they concluded that temperature change is a potential cause of CO₂ concentration change while causality in the opposite direction can be excluded as violating a necessary condition of causality. This result is opposite to the common belief that in the recent decades human CO₂ emissions are the cause of CO₂ and temperature increase.
