Kyoto Protocol Gases
“Greenhouse gas” sounds like it should mean one thing. In carbon accounting it means a specific, agreed list — the gases the world decided to count when it wrote its first binding climate treaty. Everything a company reports as its carbon footprint, from a delivery van’s exhaust to a refrigerant leak, is one of just seven substances on that list.
The Kyoto Protocol gases are the seven greenhouse gases that carbon accounting actually counts — the basket behind every “CO₂-equivalent” figure.
The Kyoto Protocol gases are the seven greenhouse gases counted in GHG accounting: carbon dioxide, methane, nitrous oxide, HFCs, PFCs, SF₆ and NF₃, added in 2012. Inventories combine them into one CO₂-equivalent figure using each gas’s GWP.
Definition — What the Kyoto Gases Are
The Kyoto Protocol gases — often just “the Kyoto gases” — are the greenhouse gases that international climate agreements and greenhouse-gas accounting standards agree to count. When the Kyoto Protocol was adopted in 1997, it defined a “basket” of six greenhouse gases that participating countries had to control and report. That list became the foundation of modern carbon accounting: the same gases are required in national inventories under the UNFCCC and in corporate inventories under the GHG Protocol.
The basket grew by one in 2012, when nitrogen trifluoride was added, bringing the total to seven. Although the Kyoto Protocol has since been succeeded by the Paris Agreement, the name endures — “Kyoto gases” is still the standard shorthand for the set of greenhouse gases that reporting covers.
The Seven Gases
The seven fall into two kinds: three individual gases, and four families of fluorinated gases. Each is converted to CO₂-equivalent using its global warming potential — shown below on the current IPCC AR6 basis.
| Gas / group | Formula | Main sources | GWP-100 (AR6) |
|---|---|---|---|
| Carbon dioxide | CO₂ | Fossil fuels, cement, land-use change | 1 |
| Methane | CH₄ | Agriculture, waste, oil & gas | 29.8* |
| Nitrous oxide | N₂O | Fertiliser, combustion, industry | 273 |
| Hydrofluorocarbons | HFCs | Refrigeration, air-conditioning | up to 14,600 |
| Perfluorocarbons | PFCs | Aluminium, semiconductors | up to 12,400 |
| Sulphur hexafluoride | SF₆ | Electrical switchgear | 24,300 |
| Nitrogen trifluoride | NF₃ | Semiconductor & display manufacturing | 17,400 |
Live GWP-100 values (IPCC AR6) from the GreenCalculus data layer · *methane fossil value shown; biogenic differs · complete AR6 dataset →
Why a “Basket”: CO₂-Equivalent
The seven gases trap heat by wildly different amounts — from CO₂ at a baseline of 1 to SF₆ at over 25,000. Adding kilograms of such different gases together would be meaningless, so accounting converts them all into a single currency: carbon dioxide equivalent (CO₂e). Each gas’s mass is multiplied by its global warming potential — its warming relative to CO₂ — and the results are summed.
This is what “the basket” means: a common metric that lets a tonne of methane, a leak of refrigerant, and a puff of SF₆ all be expressed on the same scale and totalled into one footprint. The three single gases are reported directly; the HFC and PFC “groups” cover dozens of individual compounds, each converted with its own GWP. And because those GWPs come from the IPCC, the exact numbers depend on which report is used — see AR5 vs AR6 GWP values.
What Counts, and What Doesn’t
Two clarifications catch people out. The first is that the basket grew: NF₃ was not in the original 1997 list — it was added as the seventh gas through the Kyoto Protocol’s Doha Amendment in 2012, as its use in electronics manufacturing grew.
The second is what is deliberately excluded:
- CFCs and HCFCs — potent greenhouse gases, but controlled separately under the Montreal Protocol because they also deplete the ozone layer. They are not counted in the Kyoto/GHG Protocol basket.
- Water vapour — the most abundant greenhouse gas, but not directly controlled: its atmospheric level is a consequence of temperature, not direct human emissions.
- Ground-level ozone — a greenhouse gas formed indirectly from other pollutants, not emitted or reported directly.
So “greenhouse gas”, in an accounting sense, does not mean every gas that warms the planet — it means these seven, reported to a common standard.
The Kyoto Gases in Accounting
Every corporate greenhouse-gas inventory is built from these seven gases. Under the GHG Protocol — and regimes that build on it, such as the EU’s CSRD/ESRS — a complete inventory must account for all seven wherever they are material, across Scope 1, 2, and 3. In practice CO₂ dominates most footprints, but the others are often where completeness fails: a missed refrigerant leak (HFCs), un-counted N₂O from fertiliser, or SF₆ from switchgear can each be material despite small mass, because their GWPs are so high.
Knowing the basket is therefore the starting point of any credible inventory: it defines the checklist of gases a reporter must look for before the total can be called complete.
Common Confusions
- Thinking “greenhouse gas” means any warming gas. In accounting it means these seven specifically — not water vapour, ozone, or CFCs.
- Assuming there are still only six. NF₃ was added in 2012, making seven.
- Confusing Kyoto gases with the Montreal Protocol. CFCs and HCFCs are ozone-depleting substances controlled under Montreal — they are not in the Kyoto/GHG Protocol basket.
- Counting only CO₂. A complete inventory must include all seven where material; the non-CO₂ gases are where completeness most often fails.
- Treating the HFC and PFC “groups” as single gases. Each is a family of many compounds, each with its own GWP.
- Ignoring the GWP basis. The CO₂e total depends on whether AR5 or AR6 GWP values are used.
Related Terms, Standards, and Tools
The seven Kyoto gases — CO₂, CH₄, N₂O, HFCs, PFCs, SF₆, and NF₃ — are combined into CO₂-equivalent using their global warming potentials (on the current AR6 basis) and reported under the GHG Protocol, with the full set of values in our IPCC AR6 GWP dataset.
Frequently Asked Questions
The Kyoto Protocol gases are the basket of greenhouse gases counted in greenhouse-gas accounting. The Kyoto Protocol (1997) defined six — carbon dioxide, methane, nitrous oxide, HFCs, PFCs, and sulphur hexafluoride — and nitrogen trifluoride was added as a seventh in 2012. These seven are required in corporate inventories under the GHG Protocol and in national reporting under the UNFCCC, and are combined into a single CO₂-equivalent figure using each gas’s global warming potential.
For accounting purposes there are seven: three single gases — carbon dioxide, methane, and nitrous oxide — and four groups of fluorinated gases — HFCs, PFCs, sulphur hexafluoride, and nitrogen trifluoride. The Kyoto Protocol originally listed six in 1997; NF₃ was added as the seventh in 2012. Many other substances warm the atmosphere, but these seven are the ones climate agreements and standards require to be measured and reported, so “the seven greenhouse gases” is really shorthand for the accounting basket rather than a complete list of all warming gases.
The most important exclusions are CFCs and HCFCs — themselves potent greenhouse gases, but controlled separately under the Montreal Protocol because they also deplete the ozone layer, so they are not in the Kyoto/GHG Protocol basket. Water vapour, though the most abundant greenhouse gas, is not directly controlled because its level is a consequence of temperature rather than direct emissions. Ground-level ozone is also excluded, as it forms indirectly from other pollutants. In accounting, “greenhouse gas” means the seven Kyoto gases, not every gas that warms the planet.
Nitrogen trifluoride (NF₃) was added as the seventh Kyoto gas in 2012, through the Kyoto Protocol’s Doha Amendment, which set the rules for the protocol’s second commitment period (2013–2020). NF₃ had been left out of the original 1997 basket because its use was then tiny, but the rapid growth of semiconductor and display manufacturing — where it is used to clean equipment — made it a significant and rising emission. It is now required in greenhouse-gas inventories alongside the other six gases.
Through carbon dioxide equivalent (CO₂e). Because the seven gases trap heat by very different amounts, each gas’s mass is multiplied by its global warming potential — its warming effect relative to CO₂ — and the results are added together into a single figure. CO₂ has a GWP of 1 by definition, methane around 30, nitrous oxide 273, and the fluorinated gases from the thousands into the tens of thousands. The exact GWPs come from the IPCC and depend on which assessment report is used, which is why inventories state their AR5 or AR6 basis.
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