In the recent climate change negotiations it was declared that the increase in global temperature should be kept below 2°C by 2100, relative to pre-industrial levels. China's CO₂ emissions from energy and cement processes already account for nearly 24% of global emissions, a trend that is expected to keep increasing. Thus the role of China in global GHG mitigation is crucial. A scenario analysis of China's CO₂ emissions is presented here and the feasibility of China reaching a low-carbon scenario is discussed. The results suggest that recent and continued technological progress will make it possible for China to limit its CO₂ emissions and for these emissions to peak before 2025 and therefore that the global 2°C target can be achieved. Policy relevance In signing the Copenhagen Accord, China agreed to the global 2°C target. Results from this article could be used to justify low-carbon development policies and negotiations. While many still doubt the feasibility of a low-carbon pathway to support the global 2°C target, the results suggest that such a pathway can be realistically achieved. This conclusion should increase confidence and guide the policy framework further to make possible China's low-carbon development. Related policies and measures, such as renewable energy development, energy efficiency, economic structure optimization, technology innovation, low-carbon investment, and carbon capture and storage (CCS) development, should be further enhanced. Furthermore, China can play a larger role in the international negotiations process. In the global context, the 2°C target could be reaffirmed and a global regime on an emissions mitigation protocol could be framed with countries’ emissions target up to 2050.

Biomass has been widely recognized as an important energy source with high potential to reduce greenhouse gas emissions while minimizing environmental pollution. In this study, we employ the Global Change Assessment Model to estimate the potential of agricultural and forestry residue biomass for energy production in China. Potential availability of residue biomass as an energy source was analyzed for the 21^st century under different climate policy scenarios. Currently, the amount of total annual residue biomass, averaged over 2003-2007, is around 15,519 PJ in China, consisting of 10,818 PJ from agriculture residues (70%) and 4,701 PJ forestry residues (30%). We estimate that 12,693 PJ of the total biomass is available for energy production, with 66% derived from agricultural residue and 34% from forestry residue. Most of the available residue is from South Central China (3,347 PJ), East China (2,862 PJ) and Southwest China (2,229 PJ), which combined exceeds 66% of the total national biomass. Under the reference scenario without carbon tax, the potential availability of residue biomass for energy production is projected to be 3,380 PJ by 2050 and 4,108 PJ by 2095, respectively. When carbon tax is imposed, biomass availability increases substantially. For the CCS 450 ppm scenario, availability of biomass increases to 9,002 PJ (2050) and 11,524 PJ (2095), respectively. For the 450 ppm scenario without CCS, 9,183 (2050) and 11,150 PJ (2095) residue biomass, respectively, is projected to be available. Moreover, the implementation of CCS will have a little impact on the supply of residue biomass after 2035. Our results suggest that residue biomass has the potential to be an important component in China's sustainable energy production portfolio. As a low carbon emission energy source, climate change policies that involve carbon tariff and CCS technology promote the use of residue biomass for energy production in a low carbon-constrained world.

In order to mitigate global warming and improve air quality, the transformation of regional energy structures is the most important development pathway. China, as a major global consumer of fossil fuels, will face great pressure in this regard. Aiming toward achieving the global 2 °C warming target in China, this study takes one of the most developed regions of China, Guangdong Province, as the research area in order to explore a future development pathway and potential air quality attainment until 2050, by developing two energy structure scenarios (BAU_Energy and 2Deg_Energy) and three end-of-pipe scenarios (NFC, CLE, and MTFR), and simulating future air quality and related health impacts for the different scenarios using the WRF-Chem model. The results show that under the energy transformation scenario, total energy consumption in Guangdong rises from 296 Mtce (million tons of coal equivalent) in 2015 to 329 Mtce in 2050, with electricity and clean energy accounting for 45% and 35%. In 2050, the transformation of the energy structure leads to 64%, 75%, and 46% reductions in the emissions of CO₂, NOx, and SO₂ compared with those in 2015. Together with the most stringent end-of-pipe control measures, the emissions of VOCs and primary PM_2.5 are effectively reduced by 66% and 78%. The annual average PM_2.5 and MDA8 (daily maximum 8 h O₃) concentrations in Guangdong are 33.8 and 85.9 μg/m³ in 2015, with 63.4 thousand premature deaths (95% CI: 57.1–70.8) due to environmental exposure. Under the baseline scenario, no improvement is gained in air quality or public health by 2050. In contrast, the PM_2.5 and MDA8 concentrations decline to 21.7 and 75.5 μg/m³ under the scenario with energy structure transformation, and total premature deaths are reduced to 35.5 thousand (31.9–39.5). When further combined with the most stringent end-of-pipe control measures, the PM_2.5 concentrations decrease to 16.5 μg/m³, but there is no significant improvement for ozone, with premature deaths declining to 20.6 thousand (18.5–23.0). This study demonstrates that the transformation of energy structure toward climate goals could be effective in mitigating air pollution in Guangdong and would bring significant health benefits. Compared with the end-of-pipe control policies, transformation of the energy structure is a more effective way to improve regional air quality in the long term, and synergistic promotion of both is crucial for regional development.