Modelling the climate mitigation potential of land-based CDR methods (under an uncertain climate future)

Abstract

The climate mitigation potential of terrestrial carbon dioxide removal (CDR) methods remains highly uncertain depending on the timing and magnitude of climate mitigation but also due to model uncertainty in the underlying (Earth System or vegetation) models.

STEPSEC (Scrutinizing the feasibility of TErrestrial CDR Potential under Socio-Economic Contraints) is one consortium of the research programme CDRterra (https://cdrterra.de/de). Within STEPSEC, we analyze the climate mitigation potential of terrestrial CDR methods globally and for Germany, using three dynamic global vegetation models (JSBACH, LPJmL, and LPJ-GUESS). The investigated CDR methods include afforestation/reforestation (A/R) and bioenergy plants with carbon capture and storage (BECCS). STEPSEC goes beyond assessing the carbon sequestration potentials by including ecological, social, and ethical considerations.

Within the current study, we explore global climate mitigation potentials of terrestrial CDR methods under two different climate scenarios (SSP3-7.0 and SSP1-2.6) within a highly stylized setup, where a fixed share of agricultural land is replaced by forests and bioenergy plants. This setup enables us to compare the temporal dynamics of the carbon storage efficiency of the two different CDR methods. We answer the following research questions: How does the climate potential of terrestrial CDR methods differ between regions? Does one method become more effective than the other over time? How sensitive is the climate mitigation potential to different background climates and CO2 concentrations?

For a deeper understanding of the climate impacts on A/R, we analyze the spatially differentiated global impacts of climate change on the carbon sequestration potential of three types of wood plantations (temperate, boreal, and tropical wood plantations). We show that the carbon sequestration potential of A/R would be substantially affected, with an increase in productivity in some regions and a decrease in productivity in other regions, caused by the superimposed effects of changing precipitation patterns, CO2 fertilization and temperature changes.

In a second step in this project, we will correlate the carbon storage potentials with local temperature effects from AMIP simulations and metrics for biodiversity, socio-economics and fair-burden sharing. With this interdisciplinary approach, we will identify trade-offs of high CDR potentials with other sustainability goals and equity considerations.