A team led by Abigail Swann of the University of Washington, together with Charles Koven of Lawrence Berkeley National Laboratory and colleagues across fifteen institutions, analyzed simulations from ten Earth system models run under the new flat10MIP experimental protocol, an idealized framework adopted for the Coupled Model Intercomparison Project Phase 7. Unlike earlier experiments that prescribed atmospheric carbon dioxide concentrations, flat10MIP specifies emissions directly, letting each model calculate how much carbon dioxide actually accumulates in the air as its land and ocean components absorb or release carbon. That design allows scientists to probe two crucial climate metrics, the transient climate response to cumulative emissions and the zero emissions commitment, while simultaneously tracking where carbon ends up on land.

The experimental architecture is elegantly simple. In the core flat10 experiment, carbon dioxide is emitted at a constant 10 petagrams of carbon per year, close to present-day rates, for at least a century, accumulating 1000 petagrams of cumulative emissions. From that point, two branches diverge. In the zero-emissions branch, emissions drop instantly to zero and the simulation runs for another 200 years. In the carbon-dioxide-removal branch, emissions decline steadily, turn negative, and eventually reach minus 10 petagrams per year, so that by year 300 the cumulative emissions over the whole experiment return to zero. Ten models, including ACCESS-ESM1-5, CESM2, NorESM2-LM, GFDL-ESM4, UKESM1.2, MPI-ESM1-2-LR, MIROC-ES2L, CNRM-ESM2-2, NASA-GISS-E2.1-G-CC2, and HadCM3LC-Bris, completed all three scenarios.

During the positive emissions phase, the models agreed on a broad pattern: land gained carbon, on average about 246 petagrams by year 100, and the majority of that gain, roughly 60 percent, landed in vegetation rather than soil. The mechanism is familiar. Elevated atmospheric carbon dioxide enhances photosynthesis, a process represented in every model, and the carbon flows first into leaves, wood, and roots before slowly leaking into litter and soil pools. The gains were largest in the tropics and mid-latitudes, and in most models carbon accumulated on land nearly linearly with cumulative emissions, at least through the first 1000 petagrams. A few models, notably ACCESS-ESM1-5, showed the accumulation rate tapering off earlier, as tropical gross primary productivity began to saturate under heat and moisture stress.

Then the picture darkened. When emissions were cut to zero, atmospheric carbon dioxide continued to fall as land and ocean sinks kept drawing it down, but the land’s internal accounting shifted dramatically. In seven of the ten models, tropical latitudes lost carbon during the net-zero phase, and in every single model, tropical vegetation carbon declined. Meanwhile, mid- and high-latitude regions kept gaining carbon, mostly in soils. The explanation is a cruel asymmetry. As carbon dioxide concentrations fall, the fertilization effect that boosted tropical growth partially reverses, yet temperatures remain high, accelerating respiration and stressing plants in the hottest regions. The tropics, which gained the most during the emissions phase, become the biggest losers once emissions stop.

The negative emissions branch told a similar story at a different baseline. By the point of cumulative zero emissions, when all the carbon ever emitted had hypothetically been removed, vegetation carbon had declined in most models and tropical carbon had fallen in all of them, relative to the pre-industrial starting state. Mid-latitude soils and high-latitude vegetation and soils, by contrast, often ended up above their initial stocks. The similarity between the net-zero and cumulative-zero responses suggests that the same processes, faster turnover of vegetation under heat stress and the reversal of carbon dioxide fertilization, operate in both cases, just from different starting points.

Perhaps the most striking result concerns timing. Peak atmospheric carbon dioxide arrived about 15 years before net-zero emissions, and global temperature peaked roughly 6 years after net-zero. Vegetation carbon peaked a remarkably consistent 10 years after net-zero, with a spread of only about 7 years across the ensemble, suggesting that the processes governing vegetation growth and decay are represented similarly across models. Soil carbon was another matter entirely. Its peak arrived on average 33 years after net-zero, but ranged from 9 years before to a staggering 126 years after, with GFDL-ESM4’s late peak reflecting its unusual soil model in which turnover slows as productivity rises. Because the zero emissions commitment depends on century-scale carbon sink behavior, this soil carbon disagreement directly undermines confidence in projecting how much warming will persist after emissions stop.

The study also exposed uncomfortable gaps in what the models actually contain. Pre-industrial land carbon stocks varied enormously, from 978 petagrams in GFDM-ESM4 to 3119 petagrams in NorESM2-LM, against an IPCC benchmark of about 3350 petagrams for the present day, and many models appear to hold too little soil carbon, particularly in high latitudes where permafrost processes are missing from most land components. Only three models resolve soil carbon by depth, and just two of those represent permafrost; both showed stagnation or losses of high-latitude soil carbon under zero emissions, consistent with warming-driven permafrost thaw. Even more puzzling, none of the structural differences the team examined, whether nutrient limitation, dynamic vegetation, fire, or soil complexity, correlated with model behavior. Models with and without nitrogen cycling, with one soil pool or eighty, spread across the full range of outcomes, implying that parametric uncertainty and unrepresented processes swamp the visible architecture.

That last point carries a warning for carbon dioxide removal efforts. The models in this study lack many mechanisms that would make tropical losses worse: heat damage to enzymes and reproduction, hydraulic failure and mortality, pests and pathogens, and some fire-related disturbances. The simulated tropical declines are therefore likely underestimates. And because most afforestation and reforestation projects are planned for low latitudes, precisely the regions where the models show carbon being gained and then lost, the study raises the prospect that tree-planting schemes could see their stored carbon evaporate under the sustained heat of a zero-emissions world. The idealized flat10MIP scenarios also impose removal as a boundary condition rather than modeling the physical side effects of specific removal methods, which could add further complications.

The takeaway is sobering but precise. Tropical carbon is the most likely to be gained during rising emissions and the most likely to be lost under zero, declining, and negative emissions, making it a fragile foundation for net-zero accounting. Mid- and high-latitude soils, meanwhile, behave more reliably but on timescales so uncertain and so model-dependent that they dominate the spread in the zero emissions commitment. As nations design removal portfolios and net-zero pledges, the message from this ten-model ensemble is clear: stopping emissions does not stop the carbon cycle from rearranging itself, and the places we most depend on to store carbon may be the places least able to keep it.

Subject of Research: Land carbon sink responses to positive, zero, and negative CO2 emissions across Earth system models

Article Title: Land carbon response to positive, zero, and negative CO2 emissions across Earth system models

Article References: Swann, A. L. S., Koven, C. D., Proistosecu, C., Fisher, R. A., Sanderson, B. M., Brovkin, V., Hajima, T., Jones, C. D., Kiang, N. Y., Lawrence, D. M., Liddicoat, S., Liddy, H., Romanou, A., Séférian, R., Sentman, L. T., Steinert, N. J., Tjiputra, J., & Ziehn, T. (2026). Land carbon response to positive, zero, and negative CO 2 emissions across Earth system models. Earth System Dynamics, 17(5), 1237-1275. https://doi.org/10.5194/esd-17-1237-2026

Image Credits: AI Generated

DOI: 10.5194/esd-17-1237-2026

Keywords: land carbon sink, Earth system models, net-zero emissions, negative emissions, tropical forests, soil carbon, CO2 fertilization, flat10MIP, zero emissions commitment, carbon dioxide removal, permafrost, climate modeling

One of the groundbreaking methodologies employed in this domain is the eddy covariance (EC) technique, which has revolutionized the way we collect and interpret data related to ecosystem–atmosphere exchanges. The global network of EC measurement sites, predominantly spearheaded by FLUXNET, has been instrumental in advancing our understanding of terrestrial carbon and water cycles. This extensive network has facilitated continuous, long-term measurements across a multitude of climates and ecosystems, providing researchers with invaluable data.

Since the inception of EC measurements in the early 1990s, scientists have gained unprecedented insights into the dynamic variations of carbon and water fluxes. These measurements have allowed for a nuanced understanding of fluctuations across different time scales, ranging from half-hourly data to decadal trends. Furthermore, they encompass a wide array of vegetation types and environmental gradients, revealing how these factors interact with and respond to the broader context of global change.

The significance of upscaling EC measurements cannot be overstated. Through this process, researchers have enhanced their comprehension of essential aspects such as the magnitude and spatial patterns of carbon sinks and sources. These upscaled datasets have become pivotal in elucidating the seasonal changes, interannual variability, and long-term trends in evapotranspiration and water-use efficiency. As the impacts of global change continue to unfold, these insights are crucial for understanding the health and sustainability of our ecosystems at both regional and global scales.

Moreover, EC measurements play a critical role in the validation and interpretation of satellite-derived products. This relationship between ground-based observations and remote sensing data enhances the reliability of environmental monitoring efforts. By providing a solid foundation of empirical evidence, EC data serves as a benchmark for improving terrestrial biosphere models and Earth system models, which are essential tools in predicting future scenarios and formulating mitigation strategies.

As we move forward, it is imperative that future efforts within the scientific community focus on improving the representativeness of the EC network. A more comprehensive network can enhance the accuracy and reliability of the insights gained from these measurements. Additionally, fostering open data sharing will empower researchers worldwide to collaborate and build on existing knowledge, thereby accelerating the advancement of our understanding of carbon and water cycling dynamics.

Real-time measurements must also become a priority in future research initiatives. The ability to access and analyze data as it is collected will allow for more responsive management strategies in the face of rapidly evolving environmental conditions. Improved accuracy and precision of upscaled products will further support the scientific community’s efforts in climate mitigation, ensuring that policymakers and stakeholders have access to the most reliable information available.

The complexities of carbon and water cycling in terrestrial ecosystems are compounded by the various drivers of global change. As such, understanding these systems requires multi-faceted approaches that not only leverage data but also integrate insights from various scientific disciplines. Bridging these gaps will enhance our ability to predict responses to environmental changes and develop strategies that promote resilience within ecosystems.

The importance of these findings extends beyond theoretical knowledge; they have practical implications for climate policy and management. By understanding how ecosystems function and how they respond to ongoing environmental changes, actionable strategies can be devised to enhance carbon sequestration and water conservation efforts. These strategies are vital in combating climate change and ensuring the sustainability of our planet’s resources.

In conclusion, the advancements facilitated by the global eddy covariance network underscore the necessity of continuous and comprehensive measurements of ecosystem–atmosphere exchanges. As we face unprecedented environmental challenges, the scientific community must remain committed to enhancing our understanding of these critical processes. Only through collaborative efforts and innovative research can we hope to effectively address the challenges posed by global change and move toward a more sustainable future for our ecosystems.

The integration of extensive datasets and cutting-edge modeling techniques positions researchers to unravel the complexities of terrestrial carbon and water cycling. As technology continues to evolve, the potential for increased accuracy and granularity in measurements will further empower scientists. This progress will ultimately translate into more effective management practices and robust policies aimed at safeguarding our planet.

It is crucial to recognize the role that public engagement and awareness play in this endeavor. As the scientific community aspires to produce impactful research, disseminating this knowledge to the broader public is vital. Increasing awareness of the importance of carbon and water cycling can galvanize support for research initiatives and promote grassroots movements aimed at environmental conservation.

The future of our planet hinges on the choices we make today, and fostering a culture of scientific inquiry and open collaboration is essential. As researchers harness the power of the eddy covariance technique and other innovative methodologies, the hope is to equip humanity with the tools necessary to forge a sustainable path forward. By advancing our understanding of ecosystem dynamics, we can move closer to achieving a harmonious relationship between human activity and the environment.

In this context, the findings from the ongoing research supported by the FLUXNET network are not just academic; they are instrumental in shaping the future of our interactions with the planet. By building on the foundation laid by past research, we can ensure a more resilient and sustainable world for generations to come.

Subject of Research: Ecosystem–atmosphere exchanges of carbon dioxide and water vapor; influence of global change

Article Title: Insights into terrestrial carbon and water cycling from the global eddy covariance network

Article References:

Xiao, J., Baldocchi, D., Ichii, K. et al. Insights into terrestrial carbon and water cycling from the global eddy covariance network.
Nat Rev Earth Environ (2025). https://doi.org/10.1038/s43017-025-00743-1

Image Credits: AI Generated

DOI: 10.1038/s43017-025-00743-1

Keywords: carbon cycling, water cycling, eddy covariance, FLUXNET, climate change, ecosystems, terrestrial models, environmental monitoring, sustainability, climate policy.

To combat these pressing concerns, the CONCERTO project (Improved CarbOn cycle represeNtation through multi-sCale models and Earth obseRvation for Terrestrial ecOsystems) emerges as a beacon of hope. Launched in January 2025, the project is designed to provide a holistic framework for improving our understanding and representation of terrestrial carbon cycling, ultimately aiming to reduce the invisibility that surrounds ecosystem carbon fluxes. Researchers from 13 consortium partners convened in Milan, Italy, for the project’s inaugural meeting on January 21-22, 2025. This gathering marked a crucial juncture, as it laid the foundation for a focused, four-year research agenda aimed at refining climate predictions.

What sets CONCERTO apart from its predecessors is its integrative approach. By combining leading-edge Earth observation data with innovative land surface process models, the project promises to unveil a more accurate representation of the intricate web of interactions that dictate the carbon cycle. The confluence of data assimilation techniques and machine learning algorithms will enable researchers to investigate carbon dynamics at unprecedented scales and with much greater precision than previously attainable. This synthesis of technologies equips CONCERTO to delve deeper into the terrestrial carbon cycle than any past endeavors have accomplished.

One of the keystones of this project is its emphasis on the application of innovative modeling techniques. Through advanced computational frameworks, CONCERTO aims to unravel the complexities of carbon dynamics while assisting scientists in developing robust models that can accurately forecast carbon fluxes. By emphasizing the importance of coupling terrestrial models with satellite-derived Earth observation data, the project addresses the urgent need for enhanced scientific tools and resources capable of generating reliable predictions informed by real-world observations.

Moreover, the research conducted within the CONCERTO framework is not solely relegated to academic confines; its implications extend into the realms of policy-making and climate action. As climate change accelerates, it is vital to create informed strategies based on reliable data and projections. By delivering more precise carbon cycle estimations, this project aspires to equip policymakers with the insights required to make sound decisions in the face of rapid environmental changes. The potential impact of these insights on global policies directed toward carbon neutrality is significant, providing a pathway towards a more sustainable future.

Manuela Balzarolo, the project coordinator of CONCERTO, describes the initiative as a significant stride towards enhancing Earth system models. She emphasizes that reducing uncertainties surrounding carbon cycle predictions is essential for developing effective climate mitigation strategies, which are increasingly imperative as the world grapples with the realities of climate change. Through this project, the scientific community hopes to illuminate the pathways to effective climate interventions and solutions aimed at overcoming the challenges posed by changing environmental conditions.

The role of Earth observation data is critical in ensuring the project’s success. Remotely sensed data offers a comprehensive view of land cover and use across different scales, enabling researchers to gain insights into carbon cycle processes previously difficult to access. This integration of cutting-edge remote sensing technology facilitates monitoring changes in ecosystems, quantifying carbon stores, and modeling the interactions between land use and carbon dynamics. Such advancements hold the potential to revolutionize how researchers and policymakers approach terrestrial carbon management.

Beyond just modeling and observations, CONCERTO sets out to embrace a collaborative spirit among its partners. By pooling together a diversity of expertise, ranging from ecology to computational sciences, the consortium represents a melting pot of knowledge. This collaborative effort is designed to promote cross-disciplinary discussions and enrich the research processes, ensuring that different perspectives converge to tackle the multifaceted challenges of carbon cycle dynamics comprehensively.

As the ADDITION project unfolds over the next four years, it promises a steady stream of innovative research findings and advancements. The collaborative nature will likely lead to the development of novel methodologies and interventions designed to address emerging issues surrounding carbon dynamics. These contributions are not just vital for the scientific community; they also play a crucial role in informing society’s broader understanding of climate change and its implications for sustainability.

Researchers and stakeholders interested in supporting or learning more about this groundbreaking project can access additional information through the official project website. Continuous updates will also be available on popular social channels, including LinkedIn, Bluesky, and YouTube, ensuring that interested parties remain informed about research developments and outcomes. The project’s ongoing commitment to disseminating its findings will promote transparency and awareness regarding climate science.

In the age of climate urgency, understanding the terrestrial carbon cycle is not just an academic endeavor; it’s central to our collective survival. As scientific communities rally together to answer the call for accurate modeling and representation of carbon dynamics, initiatives like CONCERTO pave the way for a more informed dialogue around environmental policy. The intersecting paths of science, technology, and policy-making must align to create innovative, impactful solutions that can navigate the unfurling challenges of climate change. To meet future challenges, we must leverage knowledge and technology to illuminate the path toward resilience and sustainability.

In summary, the CONCERTO project represents an ambitious goal of refining our understanding of terrestrial carbon dynamics through cutting-edge science and technology. As this innovative initiative progresses, it has the potential to greatly influence carbon management strategies worldwide, underscoring the importance of accuracy in climate modeling and prediction where future global policies are concerned.

Subject of Research: Terrestrial Carbon Cycle Dynamics
Article Title: CONCERTO Project: Bridging Gaps in Terrestrial Carbon Cycle Understanding
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Image Credits: Pensoft Publishers

Keywords: Carbon cycle, Climate modeling, Earth observations, Earth systems science, Observational data, Research and development, Data analysis, Machine learning, Remote sensing