Inverse modelling of New Zealand's carbon dioxide balance estimates a larger than expected carbon sink

Abstract. Accurate national-scale greenhouse gas source and sink estimates are essential to track climate mitigation efforts. Inverse models can complement inventory-based approaches for emissions reporting by providing independent estimates underpinned by atmospheric measurements, yet few nations have developed this capability for carbon dioxide (CO2). We present results from a decade-long (2011–2020) national inverse modelling study for New Zealand, which suggests a persistent carbon sink in New Zealand's terrestrial biosphere (-171±29 Tg CO2 yr−1). This sink is larger than expected from either New Zealand's Greenhouse Gas Inventory (−24 Tg CO2 yr−1) or prior terrestrial biosphere model estimates (-118±22 Tg CO2 yr−1; Biome-BGCMuSo and CenW). The largest differences are in New Zealand's South Island, in regions dominated by mature indigenous forests, generally considered to be near equilibrium, and certain grazed pasture regions. Relative to prior estimates, the inversion points to a reduced net CO2 flux to the atmosphere during the autumn/winter period. The overall findings of this study are robust with respect to extensive tests to assess the potential biases in the inverse model due to transport error, prior biosphere, ocean and fossil fuel estimates, background CO2, and diurnal cycles. We have identified CO2 exchange processes that could contribute to the gap between the inverse, prior and inventory estimates, but the magnitude of the fluxes from these processes cannot entirely explain the differences. Further work to identify the cause of the gap is essential to understand the implications of this finding for New Zealand's inventory and climate mitigation strategies.

Authors

Institutions

Publication Details

Journal
Atmospheric chemistry and physics
Published
2025-06-27
DOI
https://doi.org/10.5194/acp-25-6445-2025
Citations
1
Primary Topic
Atmospheric and Environmental Gas Dynamics
Type
article
Field-Weighted Citation Impact
1.11

Funders

Controls
|||
ALL TIME
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
article

Inverse modelling of New Zealand's carbon dioxide balance estimates a larger than expected carbon sink

Zoltán Barcza, Miko U. F. Kirschbaum, W. T. Baisden, Donna Giltrap et al.
1 citations
Atmospheric chemistry and physics
Atmospheric and Environmental Gas Dynamics
1.11
article

Inverse modelling of New Zealand's carbon dioxide balance estimates a larger than expected carbon sink

Zoltán Barcza, Miko U. F. Kirschbaum, W. T. Baisden, Donna Giltrap, Elizabeth D. Keller, Dan Smale, Stuart Moore, Jocelyn Christine Turnbull, Alex Geddes, S. E. Mikaloff Fletcher, Gordon Brailsford, Shin‐Ichiro Nakaoka, Aaron M. Wall, Louis A. Schipper, Beata Bukosa, Lìyı̌n Liáng, Andrea Brandon, Daemon Kennett, Hitoshi Mukai, Rowena Moss, Dóra Hidy, Sylvia Nichol
article en
1 citations

Abstract

Abstract. Accurate national-scale greenhouse gas source and sink estimates are essential to track climate mitigation efforts. Inverse models can complement inventory-based approaches for emissions reporting by providing independent estimates underpinned by atmospheric measurements, yet few nations have developed this capability for carbon dioxide (CO2). We present results from a decade-long (2011–2020) national inverse modelling study for New Zealand, which suggests a persistent carbon sink in New Zealand's terrestrial biosphere (-171±29 Tg CO2 yr−1). This sink is larger than expected from either New Zealand's Greenhouse Gas Inventory (−24 Tg CO2 yr−1) or prior terrestrial biosphere model estimates (-118±22 Tg CO2 yr−1; Biome-BGCMuSo and CenW). The largest differences are in New Zealand's South Island, in regions dominated by mature indigenous forests, generally considered to be near equilibrium, and certain grazed pasture regions. Relative to prior estimates, the inversion points to a reduced net CO2 flux to the atmosphere during the autumn/winter period. The overall findings of this study are robust with respect to extensive tests to assess the potential biases in the inverse model due to transport error, prior biosphere, ocean and fossil fuel estimates, background CO2, and diurnal cycles. We have identified CO2 exchange processes that could contribute to the gap between the inverse, prior and inventory estimates, but the magnitude of the fluxes from these processes cannot entirely explain the differences. Further work to identify the cause of the gap is essential to understand the implications of this finding for New Zealand's inventory and climate mitigation strategies.

Atmospheric chemistry and physicsVol. 25(12)
Eötvös Loránd University (HU), GNS Science (NZ), Ministry for the Environment (NZ), National Institute for Environmental Studies (JP), Victoria University of Wellington (NZ), National Institute of Water and Atmospheric Research (NZ), University of Waikato (NZ), Motu Economic and Public Policy Research (NZ), Manaaki Whenua – Landcare Research (NZ)
Ministry for Business Innovation and Employment
Openalex Percentile: Top 23%
Atmospheric and Environmental Gas Dynamics
1.11
DOIOpen Access PDFOpenAlex
AI Navigator

Ask Laika to Summarize, Analyze, and Connect papers live on the map.

Summarize Papers & Methodologies

Extract key findings, datasets, and comparative methods across publications.

Benchmark Rankings & Visual Analytics

Rank top research institutions, authors, funders, topics, and journals by Field-Weighted Citation Impact (FWCI) and paper volume with instant charts.

Connect Distant Disciplines

Bridge topological clusters on the map to find hidden collaborative intersections.