IPCC Sector Taxonomy in Plain Language

Last updated: 2026-05-20 · PlainEmissions Editorial

Why a common taxonomy matters

Every upstream emissions source uses its own sector categorization. UNFCCC's reporting categories (1A1, 1A2, 1B, 2A, 2B, ..., 5A) follow IPCC reporting guidelines but are organized differently than EDGAR's IPCC_for_AR6 nomenclature. Climate TRACE uses an industry-friendly category system. World Bank uses World-Bank-Indicator codes. Without a harmonization layer, the same emissions can appear in different rows in different sources.

PlainEmissions folds every upstream sub-sector into a common 8-sector hierarchy aligned with IPCC reporting categories. The taxonomy below is how every country and sector page on the site is organized.

1. Energy

The "Energy" sector covers all emissions from fuel combustion and from fossil-fuel extraction, processing, and transport — except for fugitive methane leaks, which we report separately. Sub-categories include public electricity and heat production, manufacturing industries and construction (energy use), transport (covered separately below in our hierarchy), other sectors (residential, commercial, agriculture energy use), and energy industries' own use.

Energy is by far the largest sector globally — roughly 70-75% of total CO2-equivalent emissions. It's also the easiest sector to estimate with high accuracy: fuel consumption is well-measured, emission factors are well-characterized, and the chemistry is straightforward.

2. Transport

Transport is technically a subset of energy (in IPCC reporting it's category 1A3) but we render it as its own sector because it's policy-relevant and reader-relevant in its own right. Includes road transport, rail, aviation (domestic and international), shipping (domestic and international), and other transport (off-road vehicles, recreational craft).

Aviation and international shipping are accounting oddities: they cross national borders. UNFCCC inventories typically separate domestic aviation from international aviation; the latter is reported as "memo items" not counted toward national totals. PlainEmissions follows this convention but flags it on country pages because it can be confusing.

3. Buildings

Residential and commercial heating, cooling, and appliance use. In IPCC categorization this is 1A4a (commercial/institutional) and 1A4b (residential) under the energy sector. We surface it separately because it is policy-relevant — building decarbonization is a distinct policy lever from grid decarbonization.

4. Industry

The "Industry" sector covers both energy emissions from manufacturing and process emissions from industrial chemistry. The two are very different:

Energy emissions from industry — burning natural gas to heat a steel mill, or coal to fire a cement kiln. Chemistry is just fuel combustion.
Process emissions from industry — the chemical conversion of limestone (CaCO3) to lime (CaO) in cement production releases CO2 that has nothing to do with burning fuel. Steel-making, aluminium-smelting, and chemicals manufacturing all have similar process emissions.

Process emissions are harder to abate because the chemistry, not the fuel, is the source. PlainEmissions surfaces both within the Industry sector total.

5. Agriculture

The agriculture sector covers methane from enteric fermentation (livestock digestion), methane from manure management and rice cultivation, nitrous oxide from synthetic-fertilizer application and managed soils, and other minor sources. Note that fuel-combustion emissions from agricultural equipment fall under Energy, not Agriculture.

Agriculture is roughly 10-12% of global emissions in CO2-equivalent terms but with much higher methane and N2O share than the global average — because livestock and fertilizer are the dominant sources rather than CO2 combustion.

6. Land Use & Forestry (LULUCF)

Discussed at length in our LULUCF guide. Covers carbon stock changes in vegetation and soils due to land-management activities. Can be a net source or a net sink. The most-disputed sector across all four data sources.

7. Waste

Methane from solid-waste landfilling, wastewater treatment, and waste incineration. Roughly 3-4% of global emissions in CO2-equivalent terms. Methane-capture systems at landfills can substantially reduce this number; PlainEmissions waste-sector trends often reflect landfill-management policy more than waste-generation volume.

8. Fugitive Emissions

Methane leaks from oil and gas systems and coal mining. Technically a sub-category of Energy in IPCC reporting (category 1B), but we surface it separately because of its size and because satellite observation (Climate TRACE) has dramatically improved measurement of fugitive emissions in recent years. Fugitive methane is often the largest single discrepancy between bottom-up inventories and top-down satellite observations.

Cross-walking from upstream sources

EDGAR's IPCC_for_AR6 categories fold into our hierarchy as follows: 1A1 + 1A2 + 1A4 + 1B → split across Energy + Buildings + Industry + Fugitive. 1A3 → Transport. 2 → Industry (process emissions). 3 → Agriculture. 4 → LULUCF. 5 → Waste. UNFCCC categories fold similarly. Climate TRACE's industry-friendly categories require slightly more aggregation but follow the same logic. Our database stores the upstream raw category alongside the harmonized one for traceability.

When the sector slicing matters

A country's headline CO2-equivalent total can hide important detail. Two countries with similar national totals can have completely different sector compositions — one dominated by coal-fired power (Energy), the other by deforestation (LULUCF). The implications for policy, technology, and trajectory are completely different. PlainEmissions surfaces the sector breakdown precisely so the structural composition of each country's emissions is visible, not buried.

Key takeaways

The number is downstream of the methodology — which gas, which source, which framing.
Multi-source disagreement is informative, not embarrassing — it surfaces uncertainty.
Production-based versus consumption-based; LULUCF-included versus excluded; per-capita versus absolute — each framing answers a different question.
Satellite-derived measurements (Climate TRACE) are progressively rebalancing the historical reliance on self-reported inventories.
GWP100 is convention; GWP20 dramatically reweights short-lived gases like methane.

Definitions used on this site

CO2-equivalent (CO2e): any greenhouse gas expressed as the mass of CO2 that would produce equivalent warming over a chosen time horizon, typically 100 years.
GWP100 / GWP20: global-warming potential over 100 (or 20) years; the multiplier used to convert from native gas units to CO2-equivalent.
LULUCF: Land Use, Land-Use Change, and Forestry — the IPCC sector covering carbon stocks in vegetation and soils.
Production-based emissions: emissions attributed to the country where they physically occur.
Consumption-based emissions: emissions attributed to the country where the final goods or services are consumed.
Annex I: the group of historically-developed countries under the UNFCCC with deeper reporting obligations.