Abstract
Nature-Based Climate Solutions supply carbon benefits in exchange for much-needed funding, but their credibility is challenged by the inherent variability in net drawdown (i.e., additionality) from carbon sequestration or avoided emissions, and the risk of future releases (impermanence). We recently showed how project developers can gain credibility by conservatively anticipating that all net drawdown is eventually released following a release schedule, issuing additional credits if reality is less pessimistic than projections. This paper computes optimal release schedules using ex post observations of drawdowns, balancing the competing interests of generating credits evaluated as being more permanent with limiting the risk of negative additionality. We study this approach using Monte Carlo simulations of both theoretical and real-life projects and discuss how our approach incentivises project performance. By resolving the trade-off between a credit's permanence rating and risk reduction, our approach provides a pragmatic solution to a key challenge facing project effectiveness.
Supplementary materials
Title
Supplementary Information
Description
The SI is structured in five parts:
A: formal definition of how credits and their equivalent permanence are calculated under the PACT Framework.
B, C: detailed step-by-step illustrations and mathematical representations of how we obtained the optimal release schedules
D: analytical solutions of the credit cache volume, the key quantity for the construction of optimal release schedule, in the special cases when the carbon loss distributions can be expressed as simple parametric distributions.
E: additional results of Monte Carlo simulations of theoretical projects with different net carbon drawdown levels.
F: sensitivity analyses of several key free parameters in the model and a brief discussion of the results
G: detailed information on the method for quantifying annual carbon fluxes in real-life REDD+ projects
H: additional results of Monte Carlo simulations of multiple theoretical or real-life projects aggregated into a single project portfolio.
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