Characterisation factors for greenhouse gases at a midpoint level including indirect effects based on calculations with the IMAGE model
The GWP values of this paper are a first attempt to provide a consistent set of GWP values for all direct and indirect greenhouse gases, including differences in GWP values per background scenario and flux size. The inclusion of indirect effects in GWP values causes large differences in some important greenhouse gases, which should not be ignored in LCA-analyses. We suggest for LCA purposes to use GWPs including indirect effects for marginal change and for the most realistic background scenario. However, existing uncertainties in the indirect effects of greenhouse gases demand for a better understanding of the importance of these effects.
Background, Aims and Scope
The traditional method of using Global Warming Potentials (GWPs) to assess the effects of climate change in Life Cycle Assessment (LCA) does not account for indirect atmospheric effects like saturation effects and emissions of ozone precursors. The aim of this paper is to provide GWP values for LCA purposes of the most important climate related gases including indirect effects and assess whether these values are dependent of different background conditions and size of change in emissions fluxes.
Methods
In order to reflect atmospheric interactions between direct and indirect greenhouse gases, an atmospheric climate and chemistry model needs to be used to determine GWP values. Here, the IMAGE model is used to determine GWP values for a time horizon of 100 years. Different runs were performed to test the outcomes against various background emission scenarios and various sizes in emission fluxes.
Results and Discussion
The GWP values for CO2, N2O and CH4 depend on the chosen scenario and are lower under scenarios with higher background emissions. The GWPs of Halons, PFCs and SF6 are scenario and emission flux independent. The GWPs of HFCs increase with higher background emissions and higher additional emission fluxes, whereas GWPs of CFC are scenario independent, but change when other emission fluxes are applied. Finally, GWPs of HCFCs are higher in scenarios with higher background emission scenarios, and decrease when larger emission fluxes are applied. The GWP values calculated with IMAGE with direct effects only are comparable with IPCC values. Inclusion of the indirect atmospheric effects changes some of the values positively or negatively. For CFCs this results in a value up to 70% lower. For Halons this results in a value up to 1000% lower, resulting in a strong negative GWP. Inclusion of indirect effects increases the GWP of CH4 by 50%. Newly introduced greenhouse gases which have only indirect effects are given here a GWP. SO2 has a negative GWP which depends on both the flux size and the chosen background scenario. CO and NMVOC have a positive flux-and-scenario dependent GWP. The GWP of NOx can, dependent on de chosen conditions, be positive or negative.
Authors
Specifications
- Publication title
- Characterisation factors for greenhouse gases at a midpoint level including indirect effects based on calculations with the IMAGE model
- Publication date
- 31 May 2008
- Publication type
- Publication
- Magazine
- Int J LCA 2008; 13(3):191-201