Temperature outcome of net zero emissions scenarios and China's role

The Paris Agreement calls for holding the increase in the global average temperature to well below 2C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5C. China, the largest emitter at present, will play an important role in aiming for the global 1.5 targets and has recently declared a target for achieving net zero emissions by 2060. While a range of emission pathways have been proposed toward the net zero target, their temperature implications have not been thoroughly assessed yet. To investigate the temperature implications of emission pathways supporting the net zero target, we used the ACC2 model (Tanaka et al. 2021), a simplified integrated assessment model including atmospheric chemistry, carbon cycle, climate, and economic modules. We analyzed the temperature outcome of global emissions scenarios collected from the literature (e.g. Duan et al., 2021) and looked into the difference arising from China. We further explored the temperature effect of greenhouse gas composition in the emissions scenarios by varying the emissions of CO2 and CH4 while keeping the CO2-equivalent emissions (GWP100 basis) along the pathway. This analysis intends to shed light into how different priorities of mitigation options within the zero emissions goal may imply a difference in temperatures. The evaluation results showed a large difference in the level and the year of peak temperature among these global scenarios considered. From the perspective of Chinas role in global 1.5 targets, its contribution to global warming has very large uncertainties. The temperature effect of changing greenhouse gas composition indicated that proper adjustment of greenhouse gas emissions composition while keeping the same CO2-equivalent emissions can not only help reduce the uncertainty of Chinas emission reduction plan to global climate change, but also decrease the contribution to global warming. Therefore, possible solutions that help to achieve global 1.5 targets can be proposed. References H. Duan, S. Zhou, K. Jiang, et al. Assessing Chinas efforts to pursue the 1.5 C warming limit. Science 372(6540), 378-385 (2021). K. Tanaka, O. Boucher, P. Ciais, et al. Cost-effective implementation of the Paris Agreement using flexible greenhouse gas metrics. Science Advances 7, eabf9020 (2021).