Exploring the potential carbon emissions and net-zero path of international flights: A case study in Macao.

With the rapid development of aviation industry and its increasing impact on the global climate change, the contributions of carbon emissions from international flights are attracting more and more attention worldwide. This study, taking Macao as the aviation hub, established the cross-border aviation carbon emission evaluation model to explore dynamic carbon emissions and net-zero path of international flights. The aviation hub mainly covers 58 routes and five types of civil aircraft from 12 countries or regions during 2000-2022. The results show that the aviation transportation in Macao emitted about 1.44 million tons COeq in 2019, which is high 3.6 times that of 2000. The COVID-19 has led to a rapid decline in aviation carbon emissions in a short period of time, carbon emissions in 2020 decreased by 80 % compared to 2019. In terms of cumulative carbon emissions from 2000 to 2019, the A321 and A320 Airbus contribute to 80 % of carbon emissions. And the Chinese mainland (37 %) and Taiwan (29 %) are the main sources of emissions. In 2000-2019, the proportion of carbon emissions from China (including Taiwan and Hong Kong) decrease from 91 % to 53 %, while the contribution from Southeast Asia (from 5 % to 26 %), Japan and South Korea (from 2 % to 19 %) keep the growth trends. In the optimal scenario (B3C3), net zero emissions of cross-border aviation in Macao can be not achieved, and there is still only by removing 0.3 million tons COeq. Emission reduction technology and new energy usage are priorities for the aviation emission reduction.