Global warming potential (GWP) of refrigerants: why are particular values used?

This document from UNEP’s OzonAction explains the concept of Global Warming Potential (GWP) for refrigerants and the reasons behind the use and variation of specific GWP values. It outlines how GWP measures the relative global warming effects of gases compared to carbon dioxide, the reference gas, and discusses the significance of GWP in international agreements such as the Montreal Protocol and its Kigali Amendment. The document highlights why different GWP values exist—due to updates from evolving scientific research, multiple reporting sources, and the use of various time horizons (most commonly 100 years). It provides examples of changing GWP values for substances like CFC-12, HCFC-22, and HFC-134a, referencing key IPCC and WMO assessments. The document also details how standard GWP ‘reporting values’ are now embedded in the Montreal Protocol, serving as a basis for national reporting and policy decisions.