Earlier this year, I wrote a post about a paper by Hermann Harde that argued that most of the rise in atmospheric CO2 was natural. If you want more details of why this suggestion is nonsense, you can read my earlier post. What I was going to mention in this post is that a number of us have just published a response.
The history of this is essentially that Gavin Schmidt, as he suggested in this Realclimate post, set up an Overleaf document and contacted those who had shown interest. It was lead by Peter Köhler, and colleagues, from the Alfred-Wegener-Institut, but also included myself, Eli Rabett, and Richard Zeebe from the University of Hawaii at Manoa. Gavin Cawley also provided some very valuable comments and suggestions.
I don’t need to say too much about the details of our paper. It essentially highlights that the Harde paper confuses the residence time of an individual molecule (years) with the adjustment time for an enhancement of atmospheric CO2 (centuries). It also points out that you can’t model the evolution of atmospheric CO2 with a single equation. You need to consider at least two reservoirs (atmosphere and surface ocean) and this requires at least two equations that are solved simultaneously.
We also point out that it’s important to consider the Revelle factor, which limits how much of our emissions can be taken up by the oceans (we would expect – depending on how much we emit – that 20-30% of our emissions will remain in the atmosphere for thousands of years). Additionally, there were issues with Harde’s application of his model to paleoclimate, and there were a number of papers that he really should have cited (such as citing Essenhigh 2009 paper, while failing to cite Gavin Cawley’s response).
We end our paper by suggesting that Harde’s paper be withdrawn. I’m normally a little uncomfortable with suggesting that a paper that does not involve fraud, or plagiarism, be withdrawn. However, Harde’s paper is so obviously flawed that it is remarkable that it made it through the editorial, and review, process without being rejected. It might be better if it were withdrawn, but at least there is now a formal response that highlights the numerous issues.