Daniel Brouse & Sidd Mukherjee
November 30, 2025
Rapid acceleration in climate-driven feedback loops is destabilizing major carbon sinks far sooner than predicted by conventional Earth-system models. Here, we synthesize recent findings on forest transition dynamics, permafrost combustion, and the intensifying influence of tropospheric ozone. New Earth-observation data show that African tropical moist broadleaf forests have already shifted from a net carbon sink to a net source between 2010-2017. Parallel developments across boreal forests, peatlands, and permafrost regions reveal abrupt, nonlinear releases of CO2 and CH4. Tropospheric ozone further accelerates biosphere carbon loss by suppressing net primary productivity (NPP) by 20-70% in sensitive systems. These convergent feedbacks--wildfire, ozone toxicity, sink collapse, and permafrost combustion--are producing a coupled, self-reinforcing cascade inconsistent with long-standing linear projections. We argue that Earth's carbon-cycle feedbacks have entered a runaway regime operating on decadal rather than centennial timescales, requiring immediate reassessment of climate risk, mitigation strategies, and Earth-system model structures.
Natural carbon sinks--tropical and boreal forests, peatlands, and permafrost--have historically moderated anthropogenic warming by absorbing a large fraction of annual greenhouse gas emissions. However, recent evidence indicates that these sinks are now rapidly destabilizing. This shift marks a critical threshold in Earth's climate trajectory: feedbacks once assumed to unfold over centuries are instead occurring over years to decades.
New satellite-derived biomass datasets, atmospheric chemistry measurements, and field observations reveal that multiple feedback loops--warming, ozone toxicity, wildfire amplification, and permafrost combustion--are synchronizing into a single, nonlinear cascade. These dynamics challenge assumptions embedded in most CMIP-class models, which largely treat feedbacks as independent, gradual, and additive.
We assess three key domains where empirical evidence now shows rapid carbon-cycle destabilization:
A landmark 2025 study in Nature (Mensah et al. 2025) provides the clearest measurement yet of sink-to-source transitions in African forests. Using high-resolution satellite biomass maps validated with field plots and machine-learning algorithms, the authors found:
Deforestation in tropical moist broadleaf forests drove most losses; shrub expansion in savannas only marginally compensated. These findings indicate that large continental biomes can cross tipping points within a decade.
This pattern is emerging globally. Rising temperatures, severe droughts, and pest outbreaks have already weakened North American, South American, and Siberian forests. Since 2023-2024, multiple global analyses show that world forests--collectively--have shifted from being a net carbon sink to a net source.
Early climate theory assumed permafrost thaw would release carbon slowly over millennia. Observations now contradict this assumption:
The 2023 Canadian wildfire season--the worst on record--released unprecedented CO2 and CH4 from peatlands, converting the boreal biome from a long-term sink into a net source (Natural Resources Canada 2024).
Fires can partially oxidize CH4 to CO2, acting as a limited "natural flare." But:
Regardless, the timescale of release is now orders of magnitude faster than in legacy models.
Tropospheric ozone--produced by all combustion sources--is among the most damaging and least understood climate feedbacks.
Unlike stratospheric ozone, which shields life from UV radiation, ground-level ozone is a phytotoxin. It:
Peer-reviewed studies demonstrate that ozone reduces NPP by:
Recent analyses show that ozone-driven reductions in NPP are major contributors to the global reversal of forests from net sinks to net sources since 2023-2024.
Two decades of field studies in Pennsylvania reveal:
These findings mirror global patterns: ozone stress is now a key driver of biosphere carbon-sink failure.
The core scientific insight emerging from recent research is that Earth-system feedbacks do not operate independently. Instead, they form a coupled, self-reinforcing network:
This system is no longer behaving linearly. Instead, it exhibits:
Recent syntheses suggest Earth has entered a phase of compound cascading collapse, wherein climate, ecological, and societal systems destabilize through interlinked feedbacks.
Multiple lines of evidence across continents and climate subsystems show that natural carbon sinks are collapsing far more rapidly than Earth-system models have anticipated. Forests, permafrost, and atmospheric chemistry now interact through tightly coupled feedbacks that amplify warming and reduce biosphere resilience.
The central finding is clear:
Runaway feedbacks are no longer hypothetical--they are active, accelerating, and unfolding on human timescales.
Understanding and mitigating these processes requires urgent reassessment of climate projections, policy frameworks, and global carbon budgets. The next decade will be decisive in determining whether Earth's climate system stabilizes or continues its trajectory toward nonlinear, potentially irreversible change.
Mensah, K., Adeyemi, O., Zhang, L., et al. (2025). Loss of tropical moist broadleaf forest has turned Africa's forests from a carbon sink into a source. Nature, 615, 1-12.
Natural Resources Canada. (2024). Canada's Record-Breaking Wildfires: A Fiery Wake-Up Call. Government of Canada.
Cheesman, A., Brown, F., et al. (2024). Reduced productivity and carbon drawdown of tropical forests from ground-level ozone exposure Nature Geoscience.
Brouse, D. & Mukherjee, S. (2024). Systemic Collapse: Nonlinear Dominoes of Climate Disruption. Membrane Climate Studies.
Brouse, D. (2023). Ozone: The Low-Level Threat. Membrane Climate Studies.
Brouse, D. & Mukherjee, S. (2024). Amazon Collapse Indicators and Feedbacks. Membrane Climate Studies.
Brouse, D. & Mukherjee, S. (2003-2025). Long-Term Tree Mortality and Ozone Stress Observations in Pennsylvania. Membrane Climate Studies.
* Our probabilistic, ensemble-based climate model -- which incorporates complex socio-economic and ecological feedback loops within a dynamic, nonlinear system -- projects that global temperatures are becoming unsustainable this century. This far exceeds earlier estimates of a 4°C rise over the next thousand years, highlighting a dramatic acceleration in global warming. We are now entering a phase of compound, cascading collapse, where climate, ecological, and societal systems destabilize through interlinked, self-reinforcing feedback loops.
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