GHG Science & Metrics
The atmospheric science underneath carbon accounting — the greenhouse gases, global warming potential, radiative forcing, GWP time horizons and the IPCC tiers that turn physics into emission factors.
The gases 11
What is actually in the atmosphere, and which of it an inventory counts.
Greenhouse GasGreenhouse gas (GHG): a gas that traps heat in the atmosphere — CO₂, methane, nitrous oxide and F-gases…Carbon Dioxide (CO₂)Carbon dioxide (CO₂): the main greenhouse gas from fossil fuels and the reference gas for CO₂e (GWP 1) — its…Methane (CH₄)Methane (CH₄) is a potent greenhouse gas with a GWP of 28–30 over 100 years. Definition, sources (gas…Nitrous Oxide (N₂O)Nitrous oxide (N₂O) is a greenhouse gas with a GWP of ~265 (AR5). Definition, agricultural and combustion…Fluorinated Gases (F-gases)Fluorinated gases (F-gases) are synthetic greenhouse gases - HFCs, PFCs, SF6 and NF3 - with GWPs up to…Hydrofluorocarbons (HFCs)Hydrofluorocarbons (HFCs) are ozone-safe but potent greenhouse-gas refrigerants, with GWPs up to ~14,600×…Perfluorocarbons (PFCs)Perfluorocarbons (PFCs) are fully fluorinated greenhouse gases from aluminium smelting and chipmaking, with…Sulphur Hexafluoride (SF₆)Sulphur hexafluoride (SF6) is the most potent greenhouse gas in common use — GWP ~25,200× CO₂ — used to…Nitrogen Trifluoride (NF₃)Nitrogen trifluoride (NF3) is a potent greenhouse gas (GWP ~17,400× CO₂) used to clean semiconductor…RefrigerantA refrigerant is the working fluid in fridges, air-conditioners, and heat pumps. Many are potent greenhouse…Kyoto Protocol GasesThe Kyoto Protocol gases are the seven greenhouse gases counted in carbon accounting: CO₂, CH₄, N₂O, HFCs…
Turning gases into one number 6
How seven gases become a single CO₂e figure — and the choices hidden in that.
Global Warming Potential (GWP)Global Warming Potential (GWP) measures how much heat a greenhouse gas traps versus CO₂. Definition, AR5/AR6…CO₂ Equivalent (CO₂e)CO₂ equivalent (CO₂e) converts non-CO₂ greenhouse gases to a common unit using GWP. Definition, formula, and…GWP Time HorizonThe GWP time horizon is the number of years a gas's warming is compared to CO2 over. GWP100 is the standard…AR5 vs AR6 GWP ValuesAR5 vs AR6 GWP values: the IPCC Fifth and Sixth Assessment Report global warming potentials. AR6 (2021) is…Radiative ForcingRadiative forcing is the change in Earth's energy balance (W/m2) from a climate driver. It underpins GWP…TCRE — Transient Climate Response to Cumulative EmissionsTCRE is the near-linear ratio of warming to cumulative CO₂ emissions — about 0.45°C per trillion tonnes (IPCC…
Land & biogenic carbon 5
Where the carbon cycle makes the accounting genuinely different.
Biogenic CO₂ (Memo Item)Biogenic CO₂ is carbon dioxide from recently-grown biomass. Under the GHG Protocol it is a memo item outside…AFOLU / FLAGAFOLU (Agriculture, Forestry and Other Land Use) and FLAG (Forest, Land and Agriculture) are the two…Carbon SinkA carbon sink is a reservoir — ocean, forest or soil — that absorbs more CO₂ than it releases. How sinks soak…Land-Use Change (LULUCF)Land-use change (LULUCF) is the conversion of land, such as deforestation, and the carbon-stock emissions or…Enteric FermentationEnteric fermentation is the digestive process that makes ruminant livestock — cattle, sheep, goats — produce…
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