Estimating afforestation potential in climate models more accurately
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CO₂ storage potential of forests is often unclear
Afforestation plays a central role in almost all climate scenarios that are compatible with the 1.5 or 2-degree target of the Paris Agreement. However, it is still unclear how reliably their CO₂ storage potential is represented in climate models. A research team led by Sabine Egerer and Julia Pongratz from the CDRterra consortium STEPSEC has investigated this question. Their study, published in the journal Environmental Research Letters, analyzes the (re)afforestation in eight climate models of the current CMIP6 comparison, which forms the basis for the reports of the Intergovernmental Panel on Climate Change.
Substantial discrepancies between the models
The analysis shows: The projected carbon uptake by forests varies greatly between the models. The reasons for this include differing definitions of land use types, different assumptions on historical afforestation, diverging satellite data and resolutions as well as varying model approaches to carbon dynamics.
Recommendations for improved modelling
The authors provide specific recommendations on how future models can be harmonized: A standardized representation of tree cover and the carbon cycle should help to calculate the CDR potential of forests more realistically.
Sabine Egerer emphasizes: “Afforestation currently has the largest carbon storage among terrestrial carbon dioxide removal (CDR) options and is likely to make a significant contribution to CDR in future. Deriving accurate estimates of future carbon uptake by forests from climate models is key to assessing future CDR potential.”
The study was carried out as part of Sabine Egerer’s research stay at the National Center for Atmospheric Research (NCAR) and was funded by the LMU Postdoc Support Fund. Researchers from all participating modeling centers were actively involved – a strong example of international scientific cooperation.
Publication:
Egerer, S. et al. (2025): Forestation in CMIP6: Wide model spread in tree cover and land carbon uptake, Environmental Research Letters. https://doi.org/10.1088/1748-9326/adc93e