Design and impact assessment of policies to overcome oversupply in China's national carbon market.

China has adopted a national carbon emissions trading market to promote emission reductions, but until now, overallocation of allowances suffer low carbon prices and thus to unfulfilled emission reduction goals. We report a general equilibrium modeling that indicates the flexible compliance and price adjustment mechanism of the carbon market, along with explores the solution to the oversupply of allowances in the China's national carbon market. We find that, under the current policy, the initial loose allowance allocation decreases the overall carbon price, and simultaneously the total amount of banked carbon allowances reaches 4.880 billion tons in 2030, resulting in the level of carbon price cannot achieve NDC (Nationally Determined Contribution) targets. However, by introducing carbon market price adjustment schemes, we observe that the cumulative amount of allowances can effectively reduce, enabling the carbon price rising. Importantly, the amount of the supply of allowances decreases most under the benchmark decrease scenario, which increases the emission reduction pressure of the enterprises from the beginning, leading to the largest economic losses, the price-based adjustment mechanism raises the carbon price to expected level at the minimize economic losses, and the quantity-based adjustment mechanism is more sensitive to policy parameters compared to the price -based adjustment mechanism. These findings offer a promising avenue for selecting cost-effective price adjustment mechanism to improve price mechanism design for national carbon markets.

Uncertainty quantification of CO2 emissions from China's civil aviation industry to 2050.

To mitigate aviation's carbon emissions of the aviation industry, the following steps are vital: accurately quantifying the carbon emission path by considering uncertainty factors, including transportation demand in the post-COVID-19 pandemic period; identifying gaps between this path and emission reduction targets; and providing mitigation measures. Some mitigation measures that can be employed by China's civil aviation industry include the gradual realization of large-scale production of sustainable aviation fuels and transition to 100% sustainable and low-carbon sources of energy. This study identified the key driving factors of carbon emissions by using the Delphi Method and set scenarios that consider uncertainty, such as aviation development and emission reduction policies. A backpropagation neural network and Monte Carlo simulation were used to quantify the carbon emission path. The study results show that China's civil aviation industry can effectively help the country achieve its carbon peak and carbon neutrality goals. However, to achieve the net-zero carbon emissions goal of global aviation, China needs to reduce its emissions by approximately 82%-91% based on the optimal emission scenario. Thus, under the international net-zero target, China's civil aviation industry will face significant pressure to reduce its emissions. The use of sustainable aviation fuels is the best way to reduce aviation emissions by 2050. Moreover, in addition to the application of sustainable aviation fuel, it will be necessary to develop a new generation of aircraft introducing new materials and upgrading technology, implement additional carbon absorption measures, and make use of carbon trading markets to facilitate China's civil aviation industry's contribution to reduce climate change.