Additionality of climate benefits from emission reduction and carbon dioxide removal
- 1University of California Santa Cruz
- 2University of California Riverside
- 3University of California - Santa Cruz
Abstract
Carbon dioxide removal (CDR) has been identified as a necessary complement to industrial
decarbonization for climate change mitigation. Marine CDR (mCDR) approaches, such as ocean
alkalinity enhancement (OAE) and direct ocean capture (DOC), have received considerable
attention for their potential to counteract ocean acidification while simultaneously reducing
atmospheric CO ₂ . However, most model-based assessments of mCDR efficacy either assume a
fixed background atmospheric CO ₂ value or adopt an idealized future CO ₂ trajectory, thereby
excluding impacts of important carbon cycle feedbacks that repartition carbon between the
ocean, atmosphere, and biosphere. Here, we use an Earth System Model to address three core
questions: whether the net CO ₂ effect of CDR depends on background emissions; whether CDR
technologies deployed simultaneously yield additive CO ₂ reductions; and whether there is
synergy between the radiative forcing (climate) benefits of CDR and emission reductions. We
evaluate permutations of direct air capture (DAC), OAE, and DOC, quantifying their individual
and combined CO ₂ effects under various emissions scenarios. We find that the radiative forcing
effects of emissions reductions and CDR are largely additive through time, regardless of
background emission scenario or CDR type or scale. Furthermore, any given quantity and type of
short-term CDR deployment produces a predictable, proportional and durable reduction in
atmospheric CO ₂ through time (ΔlnCO ₂ ), facilitating comparison between CDR strategies.
Finally, we show that CDR efficacy is marginally greater at low background CO ₂ , supporting the
complementary value of decarbonization and CDR in carbon management portfolios. These
findings provide a robust physical basis for the design of integrated carbon management
strategies and support pursuit of deep emissions cuts and CDR as synergistic climate levers.
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BibTeX
@article{ganey2026additionality,
title = {{Additionality of climate benefits from emission reduction and carbon dioxide removal}},
author = {Terra Ganey and Mathis Hain and Andrew Ridgwell and Adina Paytan},
journal = {Environmental Research Letters},
year = {2026},
month = oct,
doi = {10.1088/1748-9326/aebb4e},
url = {https://iopscience.iop.org/article/10.1088/1748-9326/aebb4e},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Additionality of climate benefits from emission reduction and carbon dioxide removal
AU - Terra Ganey
AU - Mathis Hain
AU - Andrew Ridgwell
AU - Adina Paytan
PY - 2026
DA - 2026/10/29
JO - Environmental Research Letters
DO - 10.1088/1748-9326/aebb4e
UR - https://iopscience.iop.org/article/10.1088/1748-9326/aebb4e
AB - Carbon dioxide removal (CDR) has been identified as a necessary complement to industrial
decarbonization for climate change mitigation. Marine CDR (mCDR) approaches, such as ocean
alkalinity enhancement (OAE) and direct ocean capture (DOC), have received considerable
attention for their potential to counteract ocean acidification while simultaneously reducing
atmospheric CO ₂ . However, most model-based assessments of mCDR efficacy either assume a
fixed background atmospheric CO ₂ value or adopt an idealized future CO ₂ trajectory, thereby
excluding impacts of important carbon cycle feedbacks that repartition carbon between the
ocean, atmosphere, and biosphere. Here, we use an Earth System Model to address three core
questions: whether the net CO ₂ effect of CDR depends on background emissions; whether CDR
technologies deployed simultaneously yield additive CO ₂ reductions; and whether there is
synergy between the radiative forcing (climate) benefits of CDR and emission reductions. We
evaluate permutations of direct air capture (DAC), OAE, and DOC, quantifying their individual
and combined CO ₂ effects under various emissions scenarios. We find that the radiative forcing
effects of emissions reductions and CDR are largely additive through time, regardless of
background emission scenario or CDR type or scale. Furthermore, any given quantity and type of
short-term CDR deployment produces a predictable, proportional and durable reduction in
atmospheric CO ₂ through time (ΔlnCO ₂ ), facilitating comparison between CDR strategies.
Finally, we show that CDR efficacy is marginally greater at low background CO ₂ , supporting the
complementary value of decarbonization and CDR in carbon management portfolios. These
findings provide a robust physical basis for the design of integrated carbon management
strategies and support pursuit of deep emissions cuts and CDR as synergistic climate levers.
SN - 1748-9326
ER -