the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 05 Oct 2023
The long-term impact of transgressing planetary boundaries on biophysical atmosphere-land interactions
Abstract. Human activities have had a significant impact on Earth's systems and processes, leading to a transition of Earth's state from the relatively stable Holocene epoch to the Anthropocene. The planetary boundaries framework characterizes major risks of destabilization, particularly in the core dimensions of climate and biosphere change. Land system change, including deforestation and urbanization, alters ecosystems and impacts the water and energy cycle between land surface and atmosphere, while climate change can disrupt the balance of ecosystems and impact vegetation composition and soil carbon pools. These drivers also interact with each other, further exacerbating their impacts. Earth system models have been used recently to illustrate the risks and interacting effects of transgressing selected planetary boundaries, but a detailed analysis is still missing. Here, we study the impacts of long-term transgressions of the climate and land system change boundaries on the Earth system using an Earth system model with an incorporated detailed dynamic vegetation model. In our centennial-scale simulation analysis, we find that transgressing the land system change boundary results in increases in global temperatures and aridity. Furthermore, this transgression is associated with a substantial loss of vegetation carbon, exceeding 200 PgC, in contrast to conditions considered safe. Concurrently, the influence of climate change becomes evident as temperatures surge by 2.7–3.1 °C depending on the region. Notably, carbon dynamics are most profoundly affected within the large carbon reservoirs of the boreal permafrost areas, where carbon emissions peak at 150 PgC. While a restoration scenario to reduce human pressure to meet the planetary boundaries of climate change and land system change proves beneficial for carbon pools and global mean temperature, a transgression of these boundaries could lead to profoundly negative effects on the Earth system and the terrestrial biosphere. Our results suggest that respecting both boundaries is essential for safeguarding Holocene-like planetary conditions that characterize a resilient Earth system and are in accordance with the goals of the Paris Climate Agreement.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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Supplement
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(9378 KB) - Metadata XML
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Supplement
(1611 KB) - BibTeX
- EndNote
- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-2133', Anonymous Referee #1, 22 Oct 2023
The research conducted by Drüke et al. offers insights into the Earth's future using the fully coupled and dynamic Earth system model, POEM. This study underscores the importance of respecting Earth's 'boundaries', demonstrating the extensive consequences of human-induced land use and climate change on the biosphere if these boundaries are overlooked or breached at various degrees. What sets this study apart is its scope: while the IPCC offers emission scenarios on climate change up to 2100, Drüke et al. delve into more extended time frames, revealing the potential long-term repercussions of human activities on both the Earth's biosphere and climate. Through detailed, spatially-explicit maps, the authors highlight both global patterns and regional disparities, showing the extensive ways human activities can alter land surfaces and climates.This work has substantial implications on the different levels of commitment that can serve as a guidance on safeguarding the planetary boundaries of land surface and climate change from a scientific point of view.
However, I'd like to address two main concerns:
First, the prescribed set-ups of climate change (CC) and land system change (LSC) are separated in the six different scenarios. The implicit assumption behind this set-up is that these two processes are relatively independent. For example, a scenario where there is low human activity but extensive climate change is presented by pairing low LSC with high CC. However, climate change and land use are interconnected: land use change influence global greenhouse gas levels, thereby affecting climate change. Conversely, a shifting climate also impacts agriculture and land use patterns. The intimate relationship between CC and LSC needs to be factored into the model. My concern is whether all the scenarios are realistic? And how does the model account for the interaction between CC and LSC?
Secondly, as showcased in Figure 2c, when LSC boundaries are crossed, vegetation carbon storage experiences a significant reduction of approximately 180 PgC due to intensive land use. Soil carbon sees only a modest increase of 60-70 PgC, attributed to an increase in litter input into the soil carbon pool, as the authors have suggested. This leaves around 110 PgC of carbon to be either burned, utilized, or decomposed, inevitably increasing emissions. Even if only half of this carbon is released into the atmosphere, it would amount to a roughly 115 ppm (55 PgC) surge in atmospheric CO2—a significant increment given the maximum CO2 level in the most drastic scenarios is 550 ppm in the modeling setup. The study's modeling efforts lock the CO2 level at a constant from 2052 onward, but for a comprehensive understanding of long-term changes, this factor should be integrated.
Lastly, a few specific comments on the manuscript:
- The manuscript could benefit from an early and clear definition of 'transgressing', as it's a central theme.
- Lines 88-90: Consider adding a sentence clarifying that the previous static vegetation model component has been superseded by LPJmL5, which permits dynamic vegetation changes.
- Line 130: Would be better to give a brief explanation on why aerosols etc. remain at 2003 level.
- Line 140: I'd recommend introducing the definition of 'transgressing' in the beginning for the readers to grasp this pivotal term from the get-go.
Citation: https://doi.org/10.5194/egusphere-2023-2133-RC1 -
AC1: 'Reply on RC1', Markus Drüke, 16 Feb 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2133/egusphere-2023-2133-AC1-supplement.pdf
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RC2: 'Comment on egusphere-2023-2133', Anonymous Referee #2, 08 Nov 2023
The manuscript addresses some of the criticisms of the Planetary Boundary framework, especially the oversimplification of a very complex topic and the missing interactions between boundaries. Given the prevalence of the PB framework in the public debate on climate change, it provides a very valuable contribution to the discussion. I have some major concerns that should be addressed before publication.
My main concerns are with the validation of the model results:
- The model used in the study tries to model highly chaotic processes over very long periods of time, especially deforestation (which depends on human behavior) and vegetation itself. The authors use single model runs, a sensitivity analysis is necessary to show uncertainty of the model results. Especially as running the model does not seem to be too expensive this should not be too difficult.
- The model is quite novel. How well does hindcasting work? This is probably the best way to verify the accuracy of model results.
- I think it is important to see the isolated effect of crossing boundaries (and I disagree with reviewer 1 here), especially because the authors put interactions between the different boundaries as one of the main aspects of your analysis. It would have been interesting to see "risky land system change" and "safe" climate change scenario, even though this is an impossible scenario. This is the only way to quantify the additional effects of crossing both boundaries.I have one minor remark: In some figure the font is unreadably small
Citation: https://doi.org/10.5194/egusphere-2023-2133-RC2 -
AC2: 'Reply on RC2', Markus Drüke, 16 Feb 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2133/egusphere-2023-2133-AC2-supplement.pdf
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AC2: 'Reply on RC2', Markus Drüke, 16 Feb 2024
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-2133', Anonymous Referee #1, 22 Oct 2023
The research conducted by Drüke et al. offers insights into the Earth's future using the fully coupled and dynamic Earth system model, POEM. This study underscores the importance of respecting Earth's 'boundaries', demonstrating the extensive consequences of human-induced land use and climate change on the biosphere if these boundaries are overlooked or breached at various degrees. What sets this study apart is its scope: while the IPCC offers emission scenarios on climate change up to 2100, Drüke et al. delve into more extended time frames, revealing the potential long-term repercussions of human activities on both the Earth's biosphere and climate. Through detailed, spatially-explicit maps, the authors highlight both global patterns and regional disparities, showing the extensive ways human activities can alter land surfaces and climates.This work has substantial implications on the different levels of commitment that can serve as a guidance on safeguarding the planetary boundaries of land surface and climate change from a scientific point of view.
However, I'd like to address two main concerns:
First, the prescribed set-ups of climate change (CC) and land system change (LSC) are separated in the six different scenarios. The implicit assumption behind this set-up is that these two processes are relatively independent. For example, a scenario where there is low human activity but extensive climate change is presented by pairing low LSC with high CC. However, climate change and land use are interconnected: land use change influence global greenhouse gas levels, thereby affecting climate change. Conversely, a shifting climate also impacts agriculture and land use patterns. The intimate relationship between CC and LSC needs to be factored into the model. My concern is whether all the scenarios are realistic? And how does the model account for the interaction between CC and LSC?
Secondly, as showcased in Figure 2c, when LSC boundaries are crossed, vegetation carbon storage experiences a significant reduction of approximately 180 PgC due to intensive land use. Soil carbon sees only a modest increase of 60-70 PgC, attributed to an increase in litter input into the soil carbon pool, as the authors have suggested. This leaves around 110 PgC of carbon to be either burned, utilized, or decomposed, inevitably increasing emissions. Even if only half of this carbon is released into the atmosphere, it would amount to a roughly 115 ppm (55 PgC) surge in atmospheric CO2—a significant increment given the maximum CO2 level in the most drastic scenarios is 550 ppm in the modeling setup. The study's modeling efforts lock the CO2 level at a constant from 2052 onward, but for a comprehensive understanding of long-term changes, this factor should be integrated.
Lastly, a few specific comments on the manuscript:
- The manuscript could benefit from an early and clear definition of 'transgressing', as it's a central theme.
- Lines 88-90: Consider adding a sentence clarifying that the previous static vegetation model component has been superseded by LPJmL5, which permits dynamic vegetation changes.
- Line 130: Would be better to give a brief explanation on why aerosols etc. remain at 2003 level.
- Line 140: I'd recommend introducing the definition of 'transgressing' in the beginning for the readers to grasp this pivotal term from the get-go.
Citation: https://doi.org/10.5194/egusphere-2023-2133-RC1 -
AC1: 'Reply on RC1', Markus Drüke, 16 Feb 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2133/egusphere-2023-2133-AC1-supplement.pdf
-
RC2: 'Comment on egusphere-2023-2133', Anonymous Referee #2, 08 Nov 2023
The manuscript addresses some of the criticisms of the Planetary Boundary framework, especially the oversimplification of a very complex topic and the missing interactions between boundaries. Given the prevalence of the PB framework in the public debate on climate change, it provides a very valuable contribution to the discussion. I have some major concerns that should be addressed before publication.
My main concerns are with the validation of the model results:
- The model used in the study tries to model highly chaotic processes over very long periods of time, especially deforestation (which depends on human behavior) and vegetation itself. The authors use single model runs, a sensitivity analysis is necessary to show uncertainty of the model results. Especially as running the model does not seem to be too expensive this should not be too difficult.
- The model is quite novel. How well does hindcasting work? This is probably the best way to verify the accuracy of model results.
- I think it is important to see the isolated effect of crossing boundaries (and I disagree with reviewer 1 here), especially because the authors put interactions between the different boundaries as one of the main aspects of your analysis. It would have been interesting to see "risky land system change" and "safe" climate change scenario, even though this is an impossible scenario. This is the only way to quantify the additional effects of crossing both boundaries.I have one minor remark: In some figure the font is unreadably small
Citation: https://doi.org/10.5194/egusphere-2023-2133-RC2 -
AC2: 'Reply on RC2', Markus Drüke, 16 Feb 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2023-2133/egusphere-2023-2133-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Markus Drüke, 16 Feb 2024
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Cited
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(9378 KB) - Metadata XML
-
Supplement
(1611 KB) - BibTeX
- EndNote
- Final revised paper