Excluding climate impacts from secondary particles (2015dx)

In the latest IPCC Assessment Report (AR 5), emissions effecting global warming are reported as direct or indirect. Direct effects could be derived from greenhouse gases such as carbon dioxide (CO2) and methane (CH4), while indirect effects come from for example NOx and SO2 emissions. The indirect effects are caused by atmospheric reactions such as formation of ozone and secondary particles.  Such reactions may decrease or increase global warming.  The present knowledge about the quantitative extent of indirect effects is weak. One reason for this is the short lifetime of emissions involved in secondary atmospheric reactions and consequently a strong dependency of local conditions. Another reason is that there are relatively few studies made, which include secondary effects, in particular from secondary particles. There is however a reasonably good consensus that NOx has a negative effect on radiative forcing.

In version 2015dx, the climate impacts from secondary particles are excluded. This implies overall positive damage costs for e.g. NOx and SO2 (i.e. increasing the environmental damage costs).

Including climate impacts from secondary particles (2015d)

In the version 2015d, the climate impacts from secondary atmospheric reactions are included. This implies overall negative damage costs for e.g. NOx and SO2 (i.e. reducing the environmental damage costs).

In cases when there are low emissions of fossil CO2 (e.g. with large share of bio fuels and significant amounts of NOx), the 2015d version might end up with net negative impact assessment results for the analysed system.

The UNEP-SETAC Life Cycle Initiative (2012-2017) has launched a flagship project to provide global guidance and build consensus on environmental LCIA indicators (see http://www.lifecycleinitiative.org/). Their recommendation is that “near-term climate forcers (NOx, SO2, black carbon, etc.) can be used in sensitivity analyses if their contribution is expected to be important, but not to be included in the climate change impact score because of very high uncertainties and important regional variability. This may change in the future as models improve”. (Levasseur 2016)*

Recommendation

It is therefore recommended that the version including these secondary impacts (2015d) is used with care (e.g. in sensitivity analyses) and by LCA practitioners and experts understanding the underlying concept.

* Levasseur A, CIRAIG – École Polytechnique de Montréal, Canada, personal communication 2016.

Description and downloading EPS

The 2000 version is replaced by the 2015 versions which can be downloaded below. For each version there is one excel file presenting the damage costs for emissions and use of natural resources and one excel file showing the calculations made for deriving damage costs via characterisation and weighting factors.