Comment on "Scrutinizing the carbon cycle and CO2residence time in the atmosphere" by H. Harde

Peter Köhler, Judith Hauck, Christoph Völker, Dieter A. Wolf-Gladrow, Martin Butzin, Joshua B. Halpern, Ken Rice, Richard E. Zeebe

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Harde (2017) proposes an alternative accounting scheme for the modern carbon cycle and concludes that only 4.3% of today's atmospheric CO2 is a result of anthropogenic emissions. As we will show, this alternative scheme is too simple, is based on invalid assumptions, and does not address many of the key processes involved in the global carbon cycle that are important on the timescale of interest. Harde (2017) therefore reaches an incorrect conclusion about the role of anthropogenic CO2 emissions. Harde (2017) tries to explain changes in atmospheric CO2 concentration with a single equation, while the most simple model of the carbon cycle must at minimum contain equations of at least two reservoirs (the atmosphere and the surface ocean), which are solved simultaneously. A single equation is fundamentally at odds with basic theory and observations. In the following we will (i) clarify the difference between CO2 atmospheric residence time and adjustment time, (ii) present recently published information about anthropogenic carbon, (iii) present details about the processes that are missing in Harde (2017), (iv) briefly discuss shortcoming in Harde's generalization to paleo timescales, (v) and comment on deficiencies in some of the literature cited in Harde (2017).
Original languageEnglish
Pages (from-to)67-71
JournalGlobal and planetary change
Publication statusPublished - 1 May 2018

Keywords / Materials (for Non-textual outputs)

  • Carbon cycle
  • Anthropogenic carbon


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