Global GHG Emissions Causal Breakdown Tree

⊕ 59 GtCO₂e total · 2019 baseline Source: IPCC AR6 WG3 + Climate Watch / WRI Click any node to expand
Energy (73.2%)
Agriculture / Land (18.4%)
Industrial Processes (5.2%)
Waste (3.2%)
High confidence
Medium confidence
Low / estimated
⚠ Important framing: This tree uses all GHGs expressed in CO₂ equivalent (GtCO₂e) — not pure fossil CO₂ only (~36.8 Gt in 2022, Global Carbon Project). The broader GHG view includes methane (CH₄) and nitrous oxide (N₂O), which are essential to understanding agriculture and waste correctly. Where the tree stops drilling down, that is a genuine data reliability limit — sector-specific databases exist but do not reconcile cleanly to a single global accounting framework at that granularity.
▶ Full source references — 8 primary sources
[1]
IPCC Sixth Assessment Report, Working Group III (AR6 WG3), 2022

Chapter 2: Emissions trends and drivers. The authoritative global GHG accounting framework. Used for top-level and sector-level totals.

ipcc.ch/report/ar6/wg3/
[2]
Climate Watch / World Resources Institute (WRI), 2019 data

CAIT database. Primary source for level 1 and level 2 sector percentages. Used by Our World in Data and widely cited in policy documents.

climatewatchdata.org
[3]
Our World in Data — "Emissions by Sector" (Hannah Ritchie & Max Roser)

Aggregation and visualization of Climate Watch / WRI data. Used for level 2 breakdowns within Energy and AFOLU sectors.

ourworldindata.org/emissions-by-sector
[4]
IEA World Energy Outlook 2023 / IEA CO₂ Emissions from Fuel Combustion

Used for level 3 breakdowns within transport subsectors and industrial energy sub-sectors. Energy-specific, does not cover process emissions.

iea.org (summary free, full report paywalled)
[5]
Global Carbon Project — Global Carbon Budget 2023

Published in Earth System Science Data (open access). Used for pure fossil CO₂ reference (~36.8 Gt 2022) and land-use emissions validation.

essd.copernicus.org
[6]
FAO FAOSTAT — Agrifood Systems Emissions

Used for livestock enteric fermentation and manure management sub-splits. Freely accessible emissions database by country and subsector.

fao.org/faostat
[7]
Global Cement & Concrete Association (GCCA) — Getting the Numbers Right, 2022

Used for cement process emissions (~3% of global GHGs). Industry self-reported data, methodologically consistent with IPCC Tier 1/2 approach.

gccassociation.org
[8]
IMO (International Maritime Organization) — Fourth GHG Study 2020

Used for shipping emissions. IMO estimates ~1.7% of global GHGs for international shipping.

imo.org
▶ How I would search for this data — methodology walkthrough

01 Start with IPCC AR6 WG3

Chapter 2 of the Working Group III report gives the most defensible global top-level breakdown. Free PDF. The "Summary for Policymakers" has the headline numbers; Chapter 2 has the sectoral detail. This anchors the 100% baseline.

02 Our World in Data as your index

Hannah Ritchie's "Emissions by sector" article is the fastest way to find level 2 numbers with source trails. Every chart links to the underlying Climate Watch / WRI CAIT database. Use it as a lookup layer, not the primary citation.

03 IEA for energy sub-sectors

The IEA's annual "CO₂ Emissions from Fuel Combustion" goes 3–4 levels deep within energy (transport modes, industrial subsectors, building types). The executive summary is free; full data requires a license. Cross-check with IEA's data portal.

04 FAO FAOSTAT for agriculture

The FAOSTAT Agrifood emissions module lets you download by subsector (enteric fermentation, manure, rice, soils, burning) by country and year. Free. It's the source that reconciles best with IPCC for AFOLU at level 3.

05 Sector-specific industry bodies for level 3+

For cement: GCCA's "Getting the Numbers Right." For steel: worldsteel.org. For aviation: ICAO's Carbon Emissions Calculator and annual environmental report. For shipping: IMO GHG Study. These are the deepest publicly reconcilable sources.

06 Where to stop — the fragmentation problem

Below level 3, global data fractures into national inventories (UNFCCC submissions), company-level CDP disclosures, and academic estimates that don't reconcile to a common denominator. You can find a number for "emissions from baking bread" — but it won't meaningfully add back up to 100% of global GHGs. That's where this tree stops.