Complacency in the quantification and reporting of climate impacts as carbon dioxide equivalent emissions

Abstract

Listen

Translate article

PurposeThe choice of characterization model has the potential to profoundly influence LCA results and conclusions. It is therefore a requirement of ISO 14044:2006 that the selection of characterization model shall be both justified and consistent with goal and scope. The purpose of this article was to examine current practices regarding the characterization of GHG emissions and reporting as CO2 equivalent emissions.MethodsA survey of practice was conducted across articles recently published in the International Journal of Life Cycle Assessment. Each article was examined using seven predetermined questions covering reporting of CO2 equivalent emissions and justification of climate metric used, interpretation of results in relation to climate measures or goals, and the implications of choosing an alternative climate metric.Results and discussionOf the sample of 85 articles, more than half reported GHG emissions as CO2 equivalent emissions. Of these, 81% unambiguously reported the climate metric used. Most often, there was no justification for the choice of a characterization model. Where a justification was given, the most common reason was alignment with the requirements of a program or PCR document. In some cases, the choice of characterization model was determined by the choice of impact assessment method (e.g., CML, ReCiPe). In other cases, the choice of characterization model was based on the desire to compare results to other studies. It is noted that none of the abovementioned reasons is scientific justification related to a stated climate objective. Not surprisingly, most studies made no attempt to interpret results reported as CO2 equivalent emissions in relation to climate measures or goals, and most did not discuss the potential implications of alternative climate metrics. For almost half of the articles, the choice of climate metric was assessed as potentially having major implications for decision-making or comparison to alternative systems.ConclusionsBased on this survey, it is evident that key aspects of ISO 14044:2006 are routinely not being followed. When GHG emissions are aggregated into a single impact category indicator result, there is a loss of transparency about climate impacts over time and the potential to unknowingly trade short-term climate benefits against the exacerbation of the difficulties of achieving long-term climate stabilization. As such, whenever GHG emissions are reported as CO2 equivalent emissions, it is imperative that the choice of characterization model is unambiguously reported and justified, that results are interpreted in relation to environmental outcomes, and that the potential implications of selecting alternative models are discussed.Graphical