What is Global Warming Potential?
Global Warming Potential (GWP) is a measure of how much heat a greenhouse gas traps in the atmosphere over a given time period, relative to carbon dioxide (CO₂). It is the scientific basis for the CO₂e unit used throughout Root’s dashboards.
GWP values are determined by the Intergovernmental Panel on Climate Change (IPCC) through its Assessment Reports, and are updated as climate science advances.
How GWP is calculated
GWP is calculated by comparing the total heat absorbed by a given mass of a gas over a specific time horizon, to the same mass of CO₂ over the same period. CO₂ is used as the reference point with a GWP of 1.
The formula:
CO₂e = mass of gas (kg) × GWP value
GWP values for key greenhouse gases (IPCC AR6, 100-year)
Gas | Source | GWP (100-year) |
Carbon dioxide (CO₂) | Fossil fuels, land use change | 1 |
Methane (CH₄) | Natural gas, livestock, waste | 29.8 |
Nitrous oxide (N₂O) | Agriculture, combustion | 273 |
HFC-134a | Refrigerants | 1,530 |
HFC-23 | Industrial processes | 14,600 |
Sulphur hexafluoride (SF₆) | Electrical equipment | 25,200 |
This is why refrigerant leakage — even in small quantities — can have a disproportionately large climate impact.
The 100-year vs 20-year time horizon debate
GWP can be calculated over different time horizons — most commonly 20 years (GWP20) or 100 years (GWP100). The choice has significant implications:
Time horizon | Methane GWP | Implication |
GWP20 | ~80 | Emphasises near-term climate impacts; methane appears much more dangerous |
GWP100 | ~30 | Standard for most reporting; methane’s impact is averaged over a longer period |
Root uses GWP100 — the 100-year time horizon — because it is:
The standard required by GHG Protocol, CSRD, and ISO 14064
The basis for national emissions inventories and international climate agreements
Consistent with the EF methodology characterisation factors
The debate around GWP20 vs GWP100 is ongoing in the scientific community, particularly for sectors with high methane emissions (agriculture, oil and gas). Some reporting frameworks are beginning to require both to be disclosed.
What this means for your Root footprint
Every CO₂e figure in Root is calculated using GWP100 values from IPCC AR6 (the latest Assessment Report)
Methane emissions in your supply chain — such as from natural gas use in facilities — are automatically converted using the appropriate GWP factor
Refrigerant leakage impacts in the Facilities chapter are calculated using the specific GWP of each refrigerant type
When ecoinvent datasets are updated to reflect newer IPCC assessment rounds, Root’s results will reflect those updates
FAQ
Why did my carbon footprint change even though I didn’t change my data?
IPCC periodically revises GWP values as climate science improves. If Root or ecoinvent updates to a newer IPCC assessment round, characterisation factors change and your CO₂e results may shift slightly — even with identical input data. This is normal and reflects improved scientific understanding.
Does Root account for biogenic CO₂?
Biogenic CO₂ (released from burning or decomposing biological materials like wood or plant-based fibres) is treated differently from fossil CO₂ in some LCA frameworks. Root follows ecoinvent and EF methodology conventions for biogenic carbon accounting.