Radiative forcing climate footprints in the agricultural sector: Comparison of models from the IPCC 5th and 6th Assessment Reports

To achieve the goal in the Paris Agreement of limiting mean global temperature rise to 1.5 ​°C, total anthropogenic radiative forcing (RF) should be reduced from current 2.7 to around 1.9 ​W ​m−2. A newly developed RF-based climate footprint (RFCF) indicator, which quantifies the additional contribution to RF associated with current and historical emissions, can support transparent alignment with climate stabilization targets by assessing the profile of RF over time. Nevertheless, RFCF applications to date have been based on parameters and equations from IPCC 5th Assessment Report (AR). Considering the latest updates in the IPCC 6th AR, we applied the RFCF approach for the first time in a case study involving the Australian agricultural sector. We compared the RF, RFCF and annual changes in RFCF of CH4, N2O and CO2 using both models. All the results of RF as well as RFCF calculated using the latest model were slightly lower than those obtained using the former model. The agricultural sector's contribution to RF had plateaued in recent years and is projected to reach the point of net zero increase in 2022 (IPCC 6th AR model) or 2023 (IPCC 5th AR model). Considering the latest updates in emission lifetime, radiative efficiency and indirect effects based on the background concentration (1750–2019), the assessments based on IPCC 6th AR model provide more reliable results. However, a dynamic model is required to reflect the additional RF for the pulse emission based on the relevant climate background in the same year. The RF-based footprint approach can support national greenhouse gas emission reduction policy targets, especially for sectors with substantial biogenic methane emissions.