Report by nature geoscience, October 2025
This review article addresses the rising concern that several parts of the Earth system may abruptly transition to alternative stable states in response to anthropogenic climate and land-use change. Key subsystems, including the Greenland Ice Sheet (GrIS), the Atlantic Meridional Overturning Circulation (AMOC), the South American monsoon system (SAMS), and the Amazon rainforest, are analysed as candidates for such tipping point elements. The analysis concludes that observation-based evidence suggests the stability of these four elements has declined in recent decades. This is indicating they have moved toward critical thresholds that may be crossed within the range of unmitigated global warming.
Defining systemic instability through Early Warning Signals (EWS) and Critical Slowing Down (CSD)
Critical Slowing Down (CSD) describes the behavior of a system as its stability declines: A loss of stability: CSD occurs because the mechanisms that usually provide stability known as negative feedback loops become progressively weaker compared to the positive feedback that eventually drives the system toward a new state. Early Warning Signals (EWS) can recognize the changing balance of internal feedbacks within the system and serve as signs to a critical transition. They have been successfully identified in warnings of historical abrupt climate shift.
The accelerating risk of major climate shifts is defined by three major asymmetries in system dynamics:
- Core vulnerabilities and tipping elements: Key components of the Earth system, such as the GrIS, AMOC, SAMS, and Amazon rainforest, may exhibit abrupt transitions between alternative stable states in response to gradual changes. These subsystems are coupled through oceanic and atmospheric circulation patterns.
- Tipping cascades and the driving factor: Dynamical interactions between these coupled elements can lead to "tipping cascades". When one subsystem undergoes a transition, it can alter the background state of a second subsystem, potentially triggering its transition. These couplings can shift the critical threshold of a subsequent element to be crossed earlier or later than expected.
- Observational strategy through early warning: Because changes in the normal state of nonlinear systems are often not informative about their stability, Early-Warning Signals (EWS) based on Critical Slowing Down (CSD) have emerged as a central method to detect approaching critical thresholds. EWS can increase the weakening negative feedback that maintains this system stability.
Intensifying competition and governance gaps are emerging
While CSD-based EWS provide valuable predictability and quantitative measures of system resilience, the intensifying destabilization exposes inherent governance and monitoring challenges, especially concerning coupled systems:
- Masking and false signals: Interactions between tipping elements can distort or obscure genuine CSD signals, potentially leading to missed warnings.
- Coupling dynamics: Tipping element cascades can result in scenarios where an abrupt change in an element causes a tipping point event in another element (like the Amazon rainforest) immediately, resulting in weak or delayed EWS. Likewise, CSD from a leading element can be transmitted into another linked element, causing false EWS that falsely suggest an approaching critical transition in the coupled element.
- Need for monitoring: Given the ecological and socio-economic consequences of crossing critical thresholds, creating a tipping element monitoring and warning system is essential. Such a system requires high quality of data to cover the relevant timescales and provide information for timely interventions.
This summary is based on extracts from the review article authored by Niklas Boers et al,. The full version can be found here.
Photo credit Christian Pfeifer on Unsplash.
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