Enhancing life cycle impact assessment from climate science: Review of recent findings and recommendations for application to LCA

Since the Global Warming Potential (GWP) was first presented in the Intergovernmental Panel on Climate Change (IPCC) First Assessment Report, the metric has been scrutinized and alternative metrics have been suggested. The IPCC Fifth Assessment Report gives a scientific assessment of the main recent findings from climate metrics research and provides the most up-to-date values for a subset of metrics and time horizons. The objectives of this paper are to perform a systematic review of available midpoint metrics (i.e. using an indicator situated in the middle of the cause-effect chain from emissions to climate change) for well-mixed greenhouse gases and near-term climate forcers based on the current literature, to provide recommendations for the development and use of characterization factors for climate change in life cycle assessment (LCA), and to identify research needs. This work is part of the ‘Global Guidance on Environmental Life Cycle Impact Assessment’ project held by the UNEP/SETAC Life Cycle Initiative and is intended to support a consensus finding workshop. In an LCA context, it can make sense to use several complementary metrics that serve different purposes, and from there get an understanding about the robustness of the LCA study to different perspectives and metrics. We propose a step-by-step approach to test the sensitivity of LCA results to different modelling choices and provide recommendations for specific issues such as the consideration of climate-carbon feedbacks and the inclusion of pollutants with cooling effects (negative metric values)

Bridging the gap between impact assessment methods and climate science

Life-cycle assessment and carbon footprint studies are widely used by decision makers to identify climate change mitigation options and priorities at corporate and public levels. These applications, including the vast majority of emission accounting schemes and policy frameworks, traditionally quantify climate impacts of human activities by aggregating greenhouse gas emissions into the so-called CO2-equivalents using the 100-year Global Warming Potential (GWP100) as the default emission metric. The practice was established in the early nineties and has not been coupled with progresses in climate science, other than simply updating numerical values for GWP100. We review the key insights from the literature surrounding climate science that are at odds with existing climate impact methods and we identify possible improvement options. Issues with the existing approach lie in the use of a single metric that cannot represent the climate system complexity for all possible research and policy contexts, and in the default exclusion of near-term climate forcers such as aerosols or ozone precursors and changes in the Earth’s energy balance associated with land cover changes. Failure to acknowledge the complexity of climate change drivers and the spatial and temporal heterogeneities of their climate system responses can lead to the deployment of suboptimal, and potentially even counterproductive, mitigation strategies. We argue for an active consideration of these aspects to bridge the gap between climate impact methods used in environmental impact analysis and climate science

Global spatially explicit CO2 emission metrics for forest bioenergy

Contains fulltext : 157086.pdf (publisher's version ) (Open Access

Global spatially explicit CO2 emission metrics for forest bioenergy - Excel version of SI tables

Item does not contain fulltextThe file includes the tables S2 and S3 from the SI in Cherubini et al. 2016. Global spatially explicit CO2 emission metrics for forest bioenergy. Scientific Reports 6. Sheet/Table S2: Emission metrics aggregated at a national level with the associated statistical analysis. For each country, we report the mean value, standard deviation (s), 5th and 95th percentile for the 50% forest residue extraction case, and the ensemble means for the cases with no residues (No res) or all residues (All res) left on the field following harvest. Sheet/Table S3: Emission flows (in 2015, maximum emission rates, and cumulative emissions over until 2100) and results aggregated at a country level for 0%, 50% and 100% residue extraction rates