Global Warming Potentials

All greenhouse gases (GHGs) are not equal. In fact, each greenhouse gas has a unique atmospheric lifetime and heat-trapping potential.

The concept of a Global Warming Potential (GWP) has been developed to allow the comparison of the ability of each greenhouse gas to trap heat in the atmosphere relative to carbon dioxide (CO₂) over a specified time horizon. Often, greenhouse gas emissions are calculated in terms of how much CO₂ would be required to produce a similar warming effect oven the chosen time horizon. This is called the carbon dioxide equivalent (CO₂ eq) value and is calculated by multiplying the amount of gas by its associated GWP.

Consistent with Decision 2/CP.3 the 100-year GWPs, provided by the Intergovernmental Panel on Climate Change (IPCC) in its Second Assessment Report (SAR) are required for inventory reporting under the United Nations Framework Convention on Climate Change (UNFCCC) and for the 1^st commitment period under the Kyoto Protocol. These GWPs are also required for facility greenhouse gas reporting, under S.46 of the Canadian Environmental Protection Act.

The IPCC conducts periodic assessments on human induced climate change as the science evolves over time. The latest assessment resulted in updated GWPs, which were presented in the Fourth Assessment Report (AR4) published in 2007.  However, the UNFCCC has not made any recommendations on which GWPs should be applied.

Global warming potentials for greenhouse gases