Seven risk types across every domain
classes carry published criteria. A hazard can hold several; a class says what kind of risk it is, never how large it is.
Global risk
A hazard is global when its occurrence, its consequences or its causal chain cross national borders and act at continental or planetary scale, so that no single country can fully assess, prevent or absorb it.
- Its characteristic footprint is continent or planet, or a single event routinely affects several countries at once.
- Or its harm propagates across borders through shared systems: trade, finance, migration, information, atmosphere, oceans, rivers or disease transmission.
- Or effective management depends on coordination among several states or on a shared global resource.
- Do not tag a hazard global only because it occurs in many countries independently; local events that are merely widespread are not global.
Catastrophic risk
A hazard is catastrophic when at least one plausible scenario for it would cause global catastrophe: a very large loss of life, the crippling of global systems, or a civilisational setback that would take generations to recover from.
- A plausible, evidence-based scenario exists in which the hazard alone, or as the trigger of a cascade, causes mass mortality or harm on a scale well beyond the largest national disasters.
- Or such a scenario disables globally critical systems, such as food supply, energy, finance, communications or governance, across many countries at once.
- Or recovery from that scenario would take generations rather than years.
- Plausibility is judged from physical science, history or structured expert judgement, not from worst imaginable cases; the tag carries no probability claim.
Existential risk
A hazard is existential when a plausible scenario for it would cause human extinction or a permanent, unrecoverable collapse of humanity's long-term potential.
- A credible mechanism exists by which the hazard could kill all or nearly all people, or leave survivors unable to rebuild a comparable civilisation.
- Or it could permanently lock humanity into a drastically worse trajectory, for example through irreversible loss of control or enduring global oppression.
- Every existential hazard is also tagged catastrophic and global.
- Apply sparingly: the tag requires a stated mechanism to the unrecoverable outcome, not only very large harm.
Emerging risk
A hazard is emerging when it is new, or is changing fast in nature, scale, likelihood or reach, and the evidence base for assessing it is still thin or immature.
- The hazard has appeared or been recognised recently, or its drivers are shifting quickly, such as new technologies, new pathogens or a changing climate.
- And historical records are short, unrepresentative or absent, so frequencies or impacts cannot yet be estimated with confidence.
- Or authoritative assessments disagree materially about its scale or mechanism.
- Review the tag regularly: a hazard stops being emerging once a stable, tested evidence base exists.
Planetary risk
A hazard is planetary when it concerns the stability of an Earth-system process: it pressures a planetary boundary, or it is, or directly drives, a tipping element whose change of state would alter the Earth system as a whole.
- The hazard is a human pressure on a regulating Earth-system process, such as climate, biosphere integrity, nutrient cycles, freshwater, land, novel entities, aerosols, ozone or ocean chemistry.
- Or it is a tipping element, or a process that can push one past its threshold.
- Its effects operate through the coupled Earth system rather than only through local damage.
- Do not tag ordinary local environmental hazards unless they aggregate into an Earth-system pressure.
Exponential risk
A hazard is exponential when its growth or diffusion is self-accelerating, through compounding technology capability, contagion, network effects or reinforcing feedback, so that its scale can outrun linear planning and response.
- A reinforcing mechanism is identified whereby the hazard's current size increases its rate of growth or spread.
- Examples of mechanisms: person-to-person or machine-to-machine transmission, compounding capability or cost decline, self-replication, adoption cascades, amplifying physical feedback.
- The window between first signal and large-scale harm can be short relative to institutional response times.
- Growth that is merely fast but driven by an external constant force does not qualify.
Frontier technology risk
A hazard is frontier-tech when it arises from frontier or fast-advancing technology, through accident, misuse, unintended system behaviour or structural effects of its deployment.
- The hazard's source is a technology at or near the leading edge of capability, such as advanced AI and autonomous systems, engineered biology, nanotechnology, geoengineering, quantum computing, neurotechnology or advanced space systems.
- And the hazard would not exist, or would be materially different in kind or scale, without that technology.
- Covers accidents, deliberate misuse, loss of control and broad societal or strategic effects of deployment.
- Mature technologies with well-characterised hazards, such as conventional industrial chemistry, are not tagged.
Risk components
Every indicator declares the risk component it measures.
Hazard
Exposure
Vulnerability
Coping capacity
Adaptive capacity
Response
Impact
Context
From hazard to recovery
Each indicator declares its place on the risk chain and its polarity, so aggregation never mixes directions silently.
Hazard
Exposure
Vulnerability
Impact
Likelihood
Risk
Capacity
Response
Financing
Outcome
11 facets of the Nexus risk taxonomy
11 facets, each a Nexus-native vocabulary (Hazard Standard domains, contexts and risk classes, Indicator Standard, the Nexus risk chain, the model registry, the functional system classes, the Universe platforms and domain packs, the programme pillars). Generated by tools/build-catalogue.mjs; every node is governed by at least one standard and every standard sits in at least one facet (tools/validate.mjs). Published as a SKOS concept scheme in machine/risk-taxonomy.ttl.