Global Warming Potential (GWP)
Global warming potential (GWP) is a measure of how much heat a greenhouse gas traps in the atmosphere over a specified time period, relative to carbon dioxide.
What is Global Warming Potential (GWP)?
GWP values allow different greenhouse gases to be compared on a common scale. Carbon dioxide has a GWP of 1 by definition. Methane (CH₄) has a GWP of approximately 28 over 100 years (GWP100), meaning one tonne of methane traps 28 times more heat than one tonne of CO₂ over a century. Nitrous oxide (N₂O) has a GWP of approximately 265. Some fluorinated gases have GWPs in the thousands.
The GWP values are published by the IPCC in its Assessment Reports. The GHG Protocol and most regulatory frameworks use GWP100 values (100-year time horizon) from the IPCC’s most recent or specified Assessment Report. The DEFRA emission factors already incorporate the relevant GWP values, so when you apply DEFRA factors, the output is automatically expressed in tonnes of CO₂e.
The choice of GWP values matters for reporting accuracy and comparability. As the IPCC updates its Assessment Reports, GWP values change slightly, which can affect reported emissions even if actual gas releases remain unchanged. Reporting entities should disclose which set of GWP values they use.
Practical Examples
A waste management company converts its methane emissions from landfill into CO₂e using the IPCC AR5 GWP100 value of 28, turning 100 tonnes of CH₄ into 2,800 tCO₂e.
A company using refrigerant R-410A (GWP of 2,088) calculates that a 5 kg leak is equivalent to 10.44 tCO₂e — more than the annual emissions of an average UK car.
A manufacturer discloses the GWP values used in its reporting (IPCC AR6) to ensure comparability with peer companies and previous reporting years.
How Climatise Helps
Climatise automatically applies the correct GWP values when converting greenhouse gas emissions to CO₂e, using DEFRA-published factors that incorporate the latest IPCC Assessment Report values.
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