The Impact of Climate Forcing Biases and the Nitrogen Cycle on Land Carbon Balance Projections
Abstract Earth System Models (ESMs) project that the terrestrial carbon sink will continue to grow as atmospheric CO2 increases, but this projection is uncertain due to biases in the simulated climate and how ESMs represent ecosystem processes. In particular, the strength of the CO2‐fertilization ef...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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American Geophysical Union (AGU)
2024-01-01
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| Series: | Journal of Advances in Modeling Earth Systems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2023MS003749 |
| _version_ | 1797299900593995776 |
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| author | Christian Seiler Sian Kou‐Giesbrecht Vivek K. Arora Joe R. Melton |
| author_facet | Christian Seiler Sian Kou‐Giesbrecht Vivek K. Arora Joe R. Melton |
| author_sort | Christian Seiler |
| collection | DOAJ |
| description | Abstract Earth System Models (ESMs) project that the terrestrial carbon sink will continue to grow as atmospheric CO2 increases, but this projection is uncertain due to biases in the simulated climate and how ESMs represent ecosystem processes. In particular, the strength of the CO2‐fertilization effect, which is modulated by nutrient cycles, varies substantially across models. This study evaluates land carbon balance uncertainties for the Canadian Earth System Model (CanESM) by conducting simulations where the latest version of CanESM's land surface component is driven offline with raw and bias‐adjusted CanESM5 climate forcing data. To quantify the impact of nutrient limitation, we complete simulations where the nitrogen cycle is enabled or disabled. Results show that bias adjustment improves model performance across most ecosystem variables, primarily due to reduced biases in precipitation. Turning the nitrogen cycle on increases the global land carbon sink during the historical period (1995–2014) due to enhanced nitrogen deposition, placing it within the Global Carbon Budget uncertainty range. During the future period (2080–2099), the simulated land carbon sink increases in response to bias adjustment and decreases in response to the dynamic carbon‐nitrogen interaction, leading to a net decrease when both factors are acting together. The dominating impact of the nitrogen cycle demonstrates the importance of representing nutrient limitation in ESMs. Such efforts may produce more robust carbon balance projections in support of global climate change mitigation policies such as the 2015 Paris Agreement. |
| first_indexed | 2024-03-07T22:58:23Z |
| format | Article |
| id | doaj.art-8d942105ef4749e39a43f0925b8d94f8 |
| institution | Directory Open Access Journal |
| issn | 1942-2466 |
| language | English |
| last_indexed | 2024-03-07T22:58:23Z |
| publishDate | 2024-01-01 |
| publisher | American Geophysical Union (AGU) |
| record_format | Article |
| series | Journal of Advances in Modeling Earth Systems |
| spelling | doaj.art-8d942105ef4749e39a43f0925b8d94f82024-02-22T16:54:50ZengAmerican Geophysical Union (AGU)Journal of Advances in Modeling Earth Systems1942-24662024-01-01161n/an/a10.1029/2023MS003749The Impact of Climate Forcing Biases and the Nitrogen Cycle on Land Carbon Balance ProjectionsChristian Seiler0Sian Kou‐Giesbrecht1Vivek K. Arora2Joe R. Melton3Climate Processes Section Climate Research Division Environment and Climate Change Canada Victoria BC CanadaCanadian Centre for Climate Modelling and Analysis Climate Research Division Environment and Climate Change Canada Victoria BC CanadaCanadian Centre for Climate Modelling and Analysis Climate Research Division Environment and Climate Change Canada Victoria BC CanadaClimate Processes Section Climate Research Division Environment and Climate Change Canada Victoria BC CanadaAbstract Earth System Models (ESMs) project that the terrestrial carbon sink will continue to grow as atmospheric CO2 increases, but this projection is uncertain due to biases in the simulated climate and how ESMs represent ecosystem processes. In particular, the strength of the CO2‐fertilization effect, which is modulated by nutrient cycles, varies substantially across models. This study evaluates land carbon balance uncertainties for the Canadian Earth System Model (CanESM) by conducting simulations where the latest version of CanESM's land surface component is driven offline with raw and bias‐adjusted CanESM5 climate forcing data. To quantify the impact of nutrient limitation, we complete simulations where the nitrogen cycle is enabled or disabled. Results show that bias adjustment improves model performance across most ecosystem variables, primarily due to reduced biases in precipitation. Turning the nitrogen cycle on increases the global land carbon sink during the historical period (1995–2014) due to enhanced nitrogen deposition, placing it within the Global Carbon Budget uncertainty range. During the future period (2080–2099), the simulated land carbon sink increases in response to bias adjustment and decreases in response to the dynamic carbon‐nitrogen interaction, leading to a net decrease when both factors are acting together. The dominating impact of the nitrogen cycle demonstrates the importance of representing nutrient limitation in ESMs. Such efforts may produce more robust carbon balance projections in support of global climate change mitigation policies such as the 2015 Paris Agreement.https://doi.org/10.1029/2023MS003749land carbon balanceclimate changeclimate forcing biasnitrogen cycle |
| spellingShingle | Christian Seiler Sian Kou‐Giesbrecht Vivek K. Arora Joe R. Melton The Impact of Climate Forcing Biases and the Nitrogen Cycle on Land Carbon Balance Projections Journal of Advances in Modeling Earth Systems land carbon balance climate change climate forcing bias nitrogen cycle |
| title | The Impact of Climate Forcing Biases and the Nitrogen Cycle on Land Carbon Balance Projections |
| title_full | The Impact of Climate Forcing Biases and the Nitrogen Cycle on Land Carbon Balance Projections |
| title_fullStr | The Impact of Climate Forcing Biases and the Nitrogen Cycle on Land Carbon Balance Projections |
| title_full_unstemmed | The Impact of Climate Forcing Biases and the Nitrogen Cycle on Land Carbon Balance Projections |
| title_short | The Impact of Climate Forcing Biases and the Nitrogen Cycle on Land Carbon Balance Projections |
| title_sort | impact of climate forcing biases and the nitrogen cycle on land carbon balance projections |
| topic | land carbon balance climate change climate forcing bias nitrogen cycle |
| url | https://doi.org/10.1029/2023MS003749 |
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