This is from:

 Response to Call for input 2023 – Issues included in the annotated agenda and related annexes of the fifth meeting of the Article 6.4 Supervisory Body 

Derik Broekhoff (Stockholm Environment Institute)

Matthew Brander (University of Edinburgh)

Lambert Schneider (Oeko-Institut) 

25 May 2023 

Snip/highlight/unedited but emphasis added:

Within carbon crediting mechanisms… the benchmark for crediting mitigation of CO2 should be whether the mitigation contributes to staying within a targeted global carbon budget.

There is no time limit on the carbon budget. If CO2 mitigation is reversed – even far in the future – it no longer contributes to staying within the budget.

There is no number of years of storage, “N,” that would make the reversal emission count less than the physical amount that was emitted.

Physical methods for tonne-year accounting (such as the “Lashof method”) only reach this conclusion because they ignore – arbitrarily – any radiative forcing caused by a reversal that occurs more than 100 years after the original  mitigation was achieved.

This convention is at odds with the science of temperature stabilization, which suggests – irrespective of timing – that once a tonne is emitted, cumulative emissions increase by one tonne, and the expected long-term temperature equilibrium increases accordingly.

Moreover, the natural uptake of CO2 by land and oceans is already incorporated in IPCC scenarios for limiting global warming to 1.5 or 2 degrees. To stay on track towards achieving these targets, any CO2 reversal at a later stage must be fully compensated for. 

Full doc:

(More to come)