Beyond net zero climate targets: a research agenda for absolute environmental sustainability assessment to support decisions at different scales

Abstract Recent years have seen a wave of net zero targets for greenhouse gas emissions. These represent translations of the Paris Agreement goal of limiting global warming to well below 2 °C to targets for central actors, such as countries, cities and companies. Net zero climate targets hold the potential of a paradigm shift in how individual actors pursue sustainability, away from incremental improvements and towards sufficient reductions in environmental burdens. To fully realize that potential, we argue in this Topical Review that net zero targets should be complemented by absolute environmental sustainability assessment (AESA). This can inform decision-makers at different scales about the environmental performance required for societies to meet the needs of their people within the environment´s carrying capacities. We identify three limitations of current net zero climate targets: (i) conflict with equity norms, (ii) involve crude quantification of upstream and downstream emissions, and (iii) risk causing burden shifts to other environmental problems. We use these three limitations to define four criteria that AESA methods should fulfill: (1) comprehensive in covering all relevant environmental problems, (2) consistent in the selection of environmental indicators and quantification of carrying capacities, (3) justice attentive in accommodating different stakeholder perspectives, and (4) granular in the representation of life cycle production technologies and their locations and timings. We find that existing AESA methods do not yet meet these four criteria and develop a research agenda for closing the gaps towards mature methods. We apply the research agenda on the case of science-based targets for nature (SBTN), demonstrating that it can guide future methodological innovation in AESA. The proposed research agenda may lead to advanced methods that reshape the practice of carrying out AESA and vastly increase its value in decision making at different scales.