ESG · the neglected Social pillar

The new Social Cost Scope1, 2 and 3

ESG ratings have learned to count carbon with precision. They still cannot see — or score — most of the human cost behind an investment. The Social Cost Scope is a measurement standard for the ‘S’ in ESG: a shared way to find that cost, draw its boundary, and put it on the books.

From the carbon ledger to the human ledger.
A measurement doctrine by Paul Gardner Brook Three scopes · two factors
01 / THE STANDARD

One unit. One boundary. Three scopes.

Carbon became manageable the moment it became measurable. The GHG Protocol gave the world three agreed boundaries and a single unit. Social cost has never had that discipline — so the Social Cost Scope supplies it: the same three-boundary logic, applied to people.

THE HUMAN LEDGER where Social Cost Scope 1, 2 and 3 resolve into a single, comparable account of human cost
Social Cost Scope 1

Direct

The cost an organisation creates first‑hand — in its own workforce and in the communities that host its operations.

Own workforce & host communities
Social Cost Scope 2

Contracted

The cost embedded in what it buys — carried by suppliers, contractors and the purchased inputs it depends on.

Suppliers & purchased inputs
Social Cost Scope 3

Lifecycle

The cost carried across the full life of the product — from extraction, through use, to disposal.

Extraction → use → disposal
02 / THE FACTORS

Two readings the headline number hides.

A single social‑cost figure can be true and still mislead — because it says nothing about who pays the cost, or when. Two original factors restore what the average erases.

I‑Factor

The Incidence Gradient

The same cost is not the same to everyone. The I‑factor records how it falls across income — and in the domains we can already measure, it lands heaviest on those least able to absorb it.

Poorest fifth7.7%
Second~6.0%
Middle~5.0%
Fourth~4.5%
Richest fifth3.6%
Share of household income taken by a €80/tCO₂ carbon price — EU‑27
2.1×the income hit on the poorest fifth versus the richest

Source: European Commission Joint Research Centre microsimulation (2024). The poorest and richest fifths are reported values; the middle three are interpolated. Measured exposure runs the same way — the poorest fifth of EU regions breathe roughly a third more PM2.5 (EEA, 2025), and lower‑middle‑income countries suffer about 1.8× the air‑pollution death rate of high‑income nations (World Bank).

T‑Factor

Temporal Displacement

A cost deferred is not a cost avoided. The T‑factor records when the cost lands — and most of it lands decades after the act that caused it. One tonne of CO₂ emitted in 1990 is the clearest measured case.

Emission
≈ $0 booked at the time
~10 yrs
Warming peaks — cost still unbooked
~30 yrs
≈ $180 landed — about 9%
By 2100
≈ $1,840 still to come — about 91%, on others
~91%of a tonne’s lifetime cost is still outstanding 30 years after it is emitted

Source: Burke et al., Nature (2026) — discounted damages per tonne emitted in 1990. The same shape holds at the macro scale: climate damage runs roughly 1–3% of world GDP by 2030, ~7–15% by 2050 and ~10–30% by 2100 (NGFS Phase V, 2024).

Sources — the I‑factor and T‑factor figures
  1. I‑factor. European Commission Joint Research Centre — Maier, De Poli & Amores, Carbon taxes on consumption: distributional implications for a just transition in the EU (JRC138420, 2024). publications.jrc.ec.europa.eu
  2. European Environment Agency — Income‑related environmental inequalities (PM2.5 exposure by region income), 2025. eea.europa.eu
  3. World Bank — Awe et al., The Global Health Cost of Ambient PM2.5 Air Pollution (2020). documents1.worldbank.org
  4. Chancel, Global carbon inequality over 1990–2019, Nature Sustainability (2022). nature.com
  5. T‑factor. Burke et al., Quantifying climate loss and damage consistent with a social cost of carbon, Nature (2026) — open summary. climateattribution.org
  6. Ricke & Caldeira, Maximum warming occurs about one decade after a CO₂ emission, Environ. Res. Lett. (2014). sciencedaily.com
  7. NGFS — Climate Scenarios, Phase V (2024). ngfs.net
  8. US EPA — Report on the Social Cost of Greenhouse Gases (2023). epa.gov

Figures use current peer‑reviewed or official sources; the retracted Kotz et al. (2024) “committed‑loss” estimate is deliberately excluded.

03 / THE ARCHITECTURE

Not another standard. The layer beneath them.

PRI, ISSB, GRI, the rating agencies and the regulators already form the scaffolding of responsible investment. What they share is a gap: no agreed unit or boundary for social cost. The Social Cost Scope is the foundation that gives them one.

PRIPrinciples for Responsible Investment — the investor commitments
ISSBSustainability disclosure standards — what gets reported
GRIImpact reporting frameworks — how impact is described
Rating agenciesESG scores and ratings — how the market reads it all
RegulatorsDisclosure mandates — CSRD and the rules that follow
↓  all rest on a missing measurement layer  ↓
THE SOCIAL COST SCOPE a shared social unit and boundary — the foundation the rest of the architecture has been built without
04 / THE GOALS

The human core of the global agenda.

The Social Cost Scope maps directly onto the UN Sustainable Development Goals that turn on people — poverty, health, education, equality, decent work and strong institutions. Where those goals ask what progress costs in human terms, the Scope is how you answer.

United Nations disclaimer. The content of this page has not been approved by the United Nations and does not reflect the views of the United Nations, its officials or its Member States. The Sustainable Development Goals are referenced here for context only; no official United Nations iconography or branding is used, and the numbered tiles are an original, house‑style representation.

About the Author

PGB
Paul Gardner Brook

Paul Gardner Brook is a former Bulge Bracket senior investment banker who writes on the intersection of geopolitics, finance, policy, strategy and energy. “The Neglected ‘S’ in ESG: From the Carbon Ledger to the Human Ledger” is the second instalment in his continuing inquiry into the Social foundations of sustainable finance, following “The Neglected ‘S’ in ESG” (October 2025).