Are single global warming potential impact assessments adequate for carbon footprints of agri-food systems?

A - Papers appearing in refereed journals

McAuliffe, G., Lynch, J., Cain, M., Buckingham, S., Rees, R. M., Collins, A. L., Allen, M., Pierrehumbert, R., Lee, M. R. F. and Takahashi, T. 2023. Are single global warming potential impact assessments adequate for carbon footprints of agri-food systems? Environmental Research Letters. 18 (8), p. 084014. https://doi.org/10.1088/1748-9326/ace204

AuthorsMcAuliffe, G., Lynch, J., Cain, M., Buckingham, S., Rees, R. M., Collins, A. L., Allen, M., Pierrehumbert, R., Lee, M. R. F. and Takahashi, T.
Abstract

The vast majority of agri-food climate-based sustainability analyses use global warming potential (GWP100) as an impact assessment, usually in isolation; however, in recent years, discussions have criticised the ‘across-the-board’ application of GWP100 in Life Cycle Assessments (LCAs),
particularly of food systems which generate large amounts of methane (CH4) and considered whether reporting additional and/or alternative metrics may be more applicable to certain
circumstances or research questions (e.g. Global Temperature Change Potential (GTP)). This paper reports a largescale sensitivity analysis using a pasture-based beef production system (a high producer of CH4 emissions) as an exemplar to compare various climatatic impact assessments: CO2 equivalents using GWP100 and GTP100, and ‘CO2-warming-equivalents’ using ‘GWP Star’, or GWP∗. The inventory for this system was compiled using data from the UK Research and
Innovation National Capability, the North Wyke Farm Platform, in Devon, SW England. LCAs can have an important bearing on: (i) policymakers’ decisions; (ii) farmer management decisions; (iii) consumers’ purchasing habits; and (iv) wider perceptions of whether certain activities can be considered ‘sustainable’ or not; it is, therefore, the responsibility of LCA practitioners and scientists to ensure that subjective decisions are tested as robustly as possible through appropriate sensitivity and uncertainty analyses. We demonstrate herein that the choice of climate impact assessment has dramatic effects on interpretation, with GWP100 and GTP100 producing substantially different
results due to their different treatments of CH4 in the context of carbon dioxide (CO2) equivalents. Given its dynamic nature and previously proven strong correspondence with climate models, out of the three assessments covered, GWP∗ provides the most complete coverage of the temporal
evolution of temperature change for different greenhouse gas emissions. We extend previous discussions on the limitations of static emission metrics and encourage LCA practitioners to
consider due care and attention where additional information or dynamic approaches may provesuperior, scientifically speaking, particularly in cases of decision support.

KeywordsLife cycle assessment; Climate change; Agriculture; Greenhouse gas emissions; Sensitive analysis; Uncertainty
Year of Publication2023
JournalEnvironmental Research Letters
Journal citation18 (8), p. 084014
Digital Object Identifier (DOI)https://doi.org/10.1088/1748-9326/ace204
Open accessPublished as ‘gold’ (paid) open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or codeS2N - Soil to Nutrition - Work package 2 (WP2) - Adaptive management systems for improved efficiency and nutritional quality
S2N - Soil to Nutrition - Work package 3 (WP3) - Sustainable intensification - optimisation at multiple scales
Resilient Farming Futures
Publisher's version
Output statusPublished
Publication dates
Online18 Jul 2023
Publication process dates
Accepted27 Jun 2023
PublisherIOP Publishing Ltd
ISSN1748-9326

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