Methodology

How the edition was made: methods, the model card, the evidence cut and its age, the acceptance record and the glossary.

9 min read0 figures12 tables6 notesNR-COUNTRY-USA-2026-BASELINE

Contents

A.1Methods

The baseline uses published values and four simple derivations. Each is shown in full so that any reader can reproduce it.

Table A.1Methods
No.	Derivation	Calculation	Result
(1)	Insured share of North American losses, 2025	93 ÷ 133	≈ 70%
(2)	Uninsured North American losses, 2025	133 − 93	US$40 bn
(3)	Share of withdrawals for power and irrigation	41 + 37	≈ 78%
(4)	Insured share of the Los Angeles wildfires	40 ÷ 53	≈ 75%

Table A.2Coupling strength scale (matrix and model card)
Strength	Definition
STRONG	a disruption in the source system has historically changed the target system’s service or output within one season
MODERATE	an effect is documented but buffered or slower
WEAK	an effect is plausible but not documented at national scale

Table A.3Status grammar
Label	Rule
Reported	value as issued by its source, with year
Inferred	reasoned from cited evidence; never a measurement
Estimated	Nexus analytical value with stated method
Scenario	conditional on stated assumptions
Expert input	structured editorial judgement awaiting evidence

A.2Model card, National Model v0

Model ID: MDL-USA-NATIONAL · v0.1
Purpose: represent the United States as coupled water, energy, food, health and biodiversity systems with forcing and transmission layers
Family: graph-based system of systems
Inputs: the cited sources of this edition; no proprietary data
Method: expert-specified coupling strengths (STRONG · MODERATE · WEAK) from evidence and analogue events
Validation: none yet, first validation against Q1 2027 Foundry evidence
Uncertainty: qualitative; strengths are hypotheses, not measurements
Domain of validity: national scale; not for state or asset-level use
Reproducibility: strength table and sources published in this edition

20couplings

typed in v0

9strong

documented within one season

7moderate

documented, buffered

4weak

plausible, undocumented

A.3The baseline evidence cut

Every Nexus edition is published from a frozen evidence cut. The baseline cut is documentary: it pins the exact edition of every source cited. Model runs begin with the first Foundry cut in Q1 2027.

Cut ID: NQ-USA-2026-Q0-1
Type: baseline documentary cut
Resolution policy: pinned · as of 30 September 2026
Sources pinned: 40 cited sources, each at the edition and retrieval date in the references
Model runs: none at baseline, analytical values are stated with their method
Digest: computed at freeze and recorded in the publication record
Supersedes: nothing, first cut of the series
Superseded by: NQ-USA-2027-Q1-1 at the Q1 2027 close

Lineage

01
source edition
02
pinned citation
03
finding
04
page
05
publication record

Table A.4From the baseline cut to the first Foundry cut
Element	Baseline 2026	Q1 2027
Sources	cited publications, pinned by edition	qualified source bindings with versions
Analysis	stated methods and editorial estimates	typed analysis specifications
Models	National Model v0 specification	model runs with receipts
Findings	twelve baseline findings	findings re-bound to the cut
Review	five passes scheduled	five passes on the exact digest

A.4Evidence age and coverage

A 2026 edition rests on evidence observed in many different years. This page shows each time base, so that no single year label hides older evidence.

Table A.5Evidence age and coverage
Indicator	Observed	Released	Cadence	Next release
Gross GHG emissions	2022	Apr 2024	annual	next inventory
Disaster losses	2025	Jan 2026	annual	Jan 2027
Billion-dollar disasters	2024	Jan 2025	retired	,
Population	2024	Dec 2024	annual	annual
Data-centre electricity share	2023	Dec 2024	periodic	next report
Water withdrawals	2015	2018	five-yearly	next national estimate
Heat-related deaths	2023	Aug 2024	periodic	new studies
Household food insecurity	2023	Dec 2024	annual	annual
Species at risk	2023	2023	periodic	next edition
Warming since 1970	to 2023	Nov 2023	periodic	next assessment

Table A.6Coverage by system at baseline
System	Coverage	Thinnest dimension
Climate forcing	GOOD	state-level downscaling
Energy	GOOD	reliability margins under new load
Finance	GOOD	insurance availability by state
Food	GOOD	aquifer dependence
Water	PARTIAL	water-use data last compiled for 2015
Health	PARTIAL	heat surge capacity
Biodiversity	PARTIAL	ecosystem condition
Digital and cyber	THIN	dependency mapping

A.5Evidence cards, two anchor sources

Issued by the Environmental Protection Agency under the UNFCCC. National coverage 1990–2022 with IPCC methods; each edition revises earlier years. Role: binds CLI-001.

EVD-USA-001

Inventory of U.S. Greenhouse Gas Emissions and Sinks¹

Issued by the U.S. Geological Survey from state and federal data, compiled every five years. Role: binds WAT-007 and the withdrawal figure.

EVD-USA-002

Estimated Use of Water in the United States in 2015⁷

Table A.7Quality dimensions at baseline
Dimension	EVD-CAN-001	EVD-CAN-002
Completeness	all sectors and gases	all categories; some modelled
Timeliness	about 16 months after the year	about three years after the year
Revision	annual back-revision	revised between compilations
Method transparency	published annexes	published methods
External validation	UNFCCC expert review	state agency review

Evidence cards to follow in Q1 2027

Fifth National Climate Assessment³, warming and frequency findings
Heat-mortality study⁹, death-certificate method
Homeowners insurance analysis²¹, ZIP-level method
Data-centre report⁶, scenario method

A.6Publication acceptance record

Editorial self-check at evidence close. Every applicable item carries a disposition; the remaining items are review, approval and deposit.

Table A.8Publication acceptance record
Group	Area	Items	Pass	N/A	Pending
D1	Identity and scope	8	8	0	0
D2	Source and data	12	9	1	2
D3	Analysis and models	12	3	8	1
D4	Findings and claims	9	8	0	1
D5	Figures, tables, maps	10	6	2	2
D6	Editorial and citations	10	8	0	2
D7	Review and approval	13	0	0	13
D8	Artefact and design	12	7	0	5
D9	Registry and release	9	0	0	9

Publication gate

Conditions met: 14 of 23 at evidence close
Blocking problems: none recorded
Open conditions: reviews, approval of the exact digest, deposit, registry pointer

Not applicable at baseline

Model runs: first runs in Q1 2027
Maps: plates in Q2 2027
Waivers: none

A.7Status words

Table A.9The status every value carries
Status	What it means
Observed	Measured directly and published by the source.
Reported	Published statistics of an official or institutional source.
Declared	Stated by the body concerned; not independently measured.
Estimated	A Nexus estimate from cited evidence, with its method in Annex A.
Modelled	Produced by a stated model from cited inputs.
Inferred	Reasoned from cited evidence; not measured.
Forecast	A projection by the cited source.
Simulated	A simulation result under stated assumptions.
Scenario	A conditional statement under stated assumptions; never a prediction.
Expert input	Expert judgement, recorded with its basis.
Candidate	Proposed for a later edition; not yet evidence.
Evidence-quality levels (EQL 1 to 5) grade the source behind a value; they are not a score of the subject.

A.8How the edition is made, released and corrected

Every edition is built from a sealed evidence cut, reviewed under three keys, signed and deposited before any site shows it as published; corrections go to Nexus Standards as change proposals and feed the next cut.

Step	What happens	Source
01 Evidence arrives from the pillars	Foundry seals observations and indicator series, Universe hands over after-action and scenario findings, and contributions are screened at every gateway, including this site’s.
02 The cut is sealed	On the cut date the evidence is pinned under one identifier, so anyone can rebuild the edition from exactly what it was built on.
03 The edition is assembled	The edition is drafted from its template and content pack. Agents may draft; they never publish and never decide.
04 The keys turn	The Global Risks Alliance turns the capital key: its steward checks that no finding reads as advice, a rating or an underwriting decision. No edition moves on until every key has been turned by a named steward.
05 The gate opens	A named approver releases one exact digest of the edition; any change after this point is a new version, never a silent edit.
06 Signed and deposited	The PDF, the web edition and the data bundle are signed together with a manifest and an RO-Crate description, and deposited on Zenodo with a concept and a version DOI.
07 Published on five sites	Only then do the five Reports sites show the edition as published, each reading it through its own lens.
08 Corrections go to Standards	Method and correction findings go to Nexus Standards as change proposals; citations, corrections and new contributions feed the next evidence cut.

A teaching model of the process, not a forecast and not a record of any run; dates and counts on this page come from the programme record. Sources: Reports governance at Global Risks Alliance (2026); Zenodo, repository of record for Reports deposits (2026).

Lifecycle, one state at a time: Draft, Computed, Evidence bound, Reviewed, Approved for release, Published, Corrected, Superseded. This edition is a draft.

A.9Glossary and abbreviations

Table A.10Series terms
Term	Meaning
Baseline Edition	the inaugural annual edition that fixes the reference state for the series
WEFH+B	water, energy, food, health and biodiversity, the national nexus core
Coupling	a typed dependency through which one system transmits to another
Protection gap	the share of losses not covered by insurance
Capability ladder	LISTED → EXISTS → ADEQUATE → TESTED → DEMONSTRATED
EQL	evidence-quality level, 1–5
Evidence cut	a frozen resolution of exact sources and versions
NNC · NLC · NWG	National Nexus Consortium · National Leadership Council · National Working Groups

Table A.11Abbreviations used in this edition
Abbreviation	Expansion
BIS	Bureau of Industry and Security
CISA	Cybersecurity and Infrastructure Security Agency
EIA	Energy Information Administration
EPA	Environmental Protection Agency
ERS	USDA Economic Research Service
FEMA	Federal Emergency Management Agency
FERC	Federal Energy Regulatory Commission
FIO	Federal Insurance Office
LBNL	Lawrence Berkeley National Laboratory
NCA5	Fifth National Climate Assessment
NERC	North American Electric Reliability Corporation
NOAA	National Oceanic and Atmospheric Administration
NSM-22	National Security Memorandum on Critical Infrastructure Security and Resilience
USGS	U.S. Geological Survey

A.10Technical annex

Table A.12Technical annex
Item	Annex	Contents	Status
A.1	Indicator definitions	the baseline indicator set, with units and sources	IN THIS EDITION
A.2	Coupling strengths	the twenty-cell matrix and its rationale	IN THIS EDITION
A.3	Scenario specification	SCN-USA-HFG-01 assumptions and signposts	IN THIS EDITION
A.4	Capability placements	rung evidence for fifteen functions	IN THIS EDITION
A.5	Model diagnostics	first runs and validation	Q1 2027
A.6	Sensitivity analyses	influence of coupling strengths	Q2 2027
A.7	State notes	atlas cards for every state and territory	Q2 2027
A.8	Review statements	pass-by-pass review record	AT RELEASE

A.1 · indicator definition, gross greenhouse-gas emissions

Construct: annual anthropogenic greenhouse-gas emissions before land-sector removals
Unit: Mt CO₂e, 100-year global warming potentials
Scope: gross total; net total includes land use, land-use change and forestry
Source: EPA Inventory 1990–2022¹
Revision: back-revised each edition
Known limits: about 16 months’ lag at release

Notes

Numbers are the edition’s reference numbers, so a note reads the same in every chapter. The full list, with every source and its licence, is in Annex C. Annex C, references

1U.S. Environmental Protection Agency (ed.), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2022. EPA, Washington, DC, April 2024.back
7C. A. Dieter, M. A. Maupin, R. R. Caldwell et al., Estimated Use of Water in the United States in 2015, Circular 1441. U.S. Geological Survey, Reston, VA, 2018.back
3A. R. Crimmins, C. W. Avery, D. R. Easterling, K. E. Kunkel, B. C. Stewart and T. K. Maycock (eds.), Fifth National Climate Assessment. U.S. Global Change Research Program, Washington, DC, 2023.back
9J. T. Howard, N. Androne, K. C. Alcover and A. R. Santos-Lozada, “Trends of heat-related deaths in the US, 1999–2023,” JAMA, vol. 332, no. 14, pp. 1203–1204, 2024.back
21Federal Insurance Office (ed.), Analyses of U.S. Homeowners Insurance Markets, 2018–2022: Climate-Related Risks and Other Factors. U.S. Department of the Treasury, Washington, DC, January 2025.back
6A. Shehabi, S. J. Smith, A. Hubbard et al., 2024 United States Data Center Energy Usage Report. Lawrence Berkeley National Laboratory, Berkeley, CA, December 2024.back

Cite this annex

Valadbaygi, S. (Ed.). (2026). Annex A: Methodology. In United States Systems Risk and Resilience Report 2026: The State of the United States’ Interdependent Systems (Baseline Edition 2026, Report No. NR-COUNTRY-USA-2026-BASELINE) [Draft under review]. The Global Centre for Risk and Innovation (GCRI).

Every citation form of the whole report, BibTeX and RIS included, is on the edition home. Cite this report