Articles | Volume 12, issue 1
Hist. Geo Space. Sci., 12, 97–110, 2021
Hist. Geo Space. Sci., 12, 97–110, 2021

Review article 26 May 2021

Review article | 26 May 2021

The temperature–CO2 climate connection: an epistemological reappraisal of ice-core messages

Pascal Richet Pascal Richet
  • Institut de Physique du Globe de Paris, 1 Rue Jussieu, 75005 Paris, France

Abstract. As simply based on fundamental logic and on the concepts of cause and effect, an epistemological examination of the geochemical analyses performed on the Vostok ice cores invalidates the marked greenhouse effect on past climate usually assigned to CO2 and CH4. In agreement with the determining role assigned to Milankovitch cycles, temperature has, instead, constantly remained the long-term controlling parameter during the past 423 kyr, which, in turn, determined both CO2 and CH4 concentrations, whose variations exerted, at most, a minor feedback on temperature itself. If not refuted, the demonstration indicates that the greenhouse effect of CO2 on 20th century and today's climate remains to be documented, as already concluded from other evidence. The epistemological weakness of current simulations originates from the fact that they do not rely on any independent evidence for the influence of greenhouse gases on climate over long enough periods of time. The validity of models will, in particular, not be demonstrated as long as at least the most important features of climate changes, namely the glacial–interglacial transitions and the differing durations of interglacial periods, remain unaccounted for. Similarly, the constant 7 kyr time lag between temperature and CO2 decreases following deglaciation is another important feature that needs to be understood. Considered in this light, the current climate debate should be considered as being the latest of the great controversies that have punctuated the march of the Earth sciences, although its markedly differs from the preceding ones by its most varied social, environmental, economical and political ramifications.

Copernicus Publications is committed to a fair, transparent, and impartial discussion of scientific findings in all our journals. This is demonstrated through our outreach activities, our decade-long advocacy of a public peer-review process, and the fact that our editors act independently of any financial or other corporate interest Copernicus Publications may have as a publisher.

This arrangement can only work on a basis of trust in our chief editors and their editorial boards and their dedication to a fair and impartial peer review. We passionately believe in this approach to academic publishing and feel affirmed by the many high-quality manuscripts we publish every day. Copernicus Publications – and thereby all our journals – are members of COPE, the Committee on Publication Ethics, and explicitly subscribe to COPE’s code of conduct for journal editors and guide for peer reviewers.

It has been brought to our attention that the article 'The temperature–CO2 climate connection: an epistemological reappraisal of ice-core messages' by Pascal Richet (Hist. Geo Space. Sci., 12, 97–110, 2021) may not have met the standard of fair and impartial peer review, concerns that we take very seriously. Any decision we take regarding this article is motivated purely by our commitment to publication ethics and scientific discourse. In the interest of transparency, we summarize relevant aspects of the case in the Copernicus statement on the review process of manuscript HGSS-2021-1.

In the light of the aspects mentioned in our statement and after conferring with the author, the HGSS editorial board, and experts in the field, Copernicus Publications has come to the decision to temporarily bar access to the article and perform a post-publication review, as recommended by COPE in such cases. Reports and the outcome of this review will be published, and the article will be handled accordingly. Regardless of the outcome, Copernicus Publications will carefully review the editorial practices and peer-review process of HGSS.

Addendum on 25 June 2021: Pascal Richet, the author of the paper, wrote a personal reply to the Copernicus statement on the review process.


Please read the editorial note first before accessing the article

Short summary
According to climate simulations, the Earth's atmosphere is warming up as a result of human emissions of greenhouse gases. But, a causality relationship between these emissions and temperatures has not been directly demonstrated. Over a period of 423 000 years, analyses of polar ice cores in fact show that CO2 was not a cause, but an effect, of the the temperature changes recorded during cycles of glaciation–deglaciation. Hence, Milakovitch cycles are the only drivers of climate change.