Remarks on MDACC

Halperin, A Simple Equation of Multi-Decadal Atmospheric Carbon Concentration Change has been placed back in review because backward extrapolation of its main results (formulas 15-16) with its datasets produced results that contradict generally accepted estimates for pre-1957 CO2 concentrations.

Some parts of the paper are not in question:

  1. The calculated current half-life of surplus atmospheric CO2 as 35-40 years can be considered valid. This empirical estimate is not novel: a number of previous empirical estimates also fall in the 27-50 years range.
  1. The rejection of the hypothesized increase of this empirical half-life (Raupach et al, 2014) stands. Note here that the non-scientific media has sensationalized and additionally misinterpreted Raupach as a “proof” of the decrease in absolute sinks, although it did not even claim that.
  1. The IPCC Bern model was correctly dismissed as a purely political construction, having nothing in common with physics. This statement is not intended as criticism of the Contributing Authors, whose high quality research has been distorted by the IPCC.
  1. The rejection of the LUC dataset for the Global Carbon Budget 2015 (GCB2015), showing a sharp decline in LUC emissions since 2000, was correct. GCB2015 elected to use official numbers from FAO: Global Forest Resource Assessment 2010 (FAO-FRA 2010), despite a clear warning in the assessment that the sources were untrustworthy.   See Notes on FAO-FRA 2010 for more detailed discussion.
  1. The physical model of the Extended Atmosphere, including the ocean surface layer, is useful and valid.

Possible errors:

  1. The author might have underestimated the impact of turbulent (eddy) diffusivity in the deep ocean, especially possible variation of the diffusion rate with the depth and geographical location.
  1. The author might have been wrong to dismiss the hypothesis that an increase of surface temperature causes significant CO2 outgassing; if this hypothesis is correct, there should be a correlation between the elevated multi-decadal average of surface temperatures and surplus CO2 in the atmosphere (not a year-to-year correlation).
  1. The Land Use Change emissions dataset used in the paper has a large margin of error, as was acknowledged by the dataset’s author. LUC emissions were roughly comparable (150% – 70%) to the LUC emissions from 1900 to 1965. Estimating LUC emissions is difficult, and the results are hard to validate.

No offense intended, but the readers should be informed that the LUC dataset’s author is affiliated with Wood Holes Research Center (WHoRCe). WHoRCe is an environmentalist organization named similarly to the well-known Wood Holes Oceanographic Institution, apparently in an attempt to mislead the public.

  1. Although it’s not likely, the generally accepted estimates for 1900-1957 CO2 concentrations might be wrong. The results of the backward extrapolation have some similarities to Beck 2007.