At the Copenhagen climate summit, there are some misunderstandings and differences of opinion on China's commitment to cut the intensity of its carbon dioxide emissions per unit of GDP by 40-45 percent by 2020 compared with the 2005 level.

?Detractors argue that China's efforts in emission cuts are not ambitious enough, and even believe that China's target does not transcend the BAU (Business As Usual) scenario.

First, we should have a comprehensive understanding of the BAU scenario in international talks on climate change. Generally, the BAU scenario means adhering to an established economic and social development path without any policy adjustment. Specifically, the BAU scenario in greenhouse gas (GHG) emissions refers to the amount of GHGs discharged in order to maintain the current economic and social development momentum.

With regard to China's BAU scenario, firstly, China's energy consumption and GHG emissions will continue to increase for a long period given that China is still at the middle stage of industrialization and in the process of accelerated urbanization. This kind of growth path, which is in line with development norms, should certainly be reflected in the BAU scenario. Secondly, the formulation of a BAU scenario is closely related to the choice of the starting point. If we take China's "10th Five-Year Plan (2001-05)", characterized by fast industrialization and urbanization as the starting point, then the policy targets proclaimed and the achievements in the "11th Five-Year Plan (2006-10)" should not be included in China's BAU scenario.

Second, the distinction between "relative reduction" and "absolute reduction" should be specified. "Relative reduction" means the amount of GHG emissions that can be reduced in the future compared with the BAU scenario by adopting suitable policies. "Relative reduction" does not mean the amount of emissions is cut to less than that of the benchmark year, rather it means less emissions than that emitted by the previous development path. It is the margin or deviation of two different development paths. "Absolute reduction" means the amount of emissions some time in the future is absolutely less than that of the benchmark year.

The two emission reduction models adopt different scenarios as well as different benchmarks. However, what is neglected by a majority of people is that when developed countries pursue "absolute reduction", it would grant them more emission quotas compared with adopting "relative reduction" if their peak amounts of historical emissions are taken as the benchmark and they commit to the same reduction range as the developing world. The story is just opposite for developing countries, for which the "relative reduction" model is more favorable.

Therefore, we cannot come to the conclusion that the path of "absolute reduction" can definitely contribute more toward curbing global warming than the approach of "relative reduction". In this regard, it is a question of different national interests. For wealthy countries that have passed the peak of emissions, the commitment of "absolute reduction" theoretically could let them discharge more than their BAU scenario, of which they are well aware.

Third, wealthy nations are demanding an exorbitant goal of emission reduction from the developing world. According to the calculation of the average value of the six SRES (special report on emission scenarios) in the fourth estimate report of the Intergovernmental Panel on Climate Change (IPCC), in order to reach the most practical target of intensity at 550ppm, if developing countries reduce emissions by 30 percent by 2020 under their BAU scenarios, the amount of emissions of developed nations not only need not to be cut to less than the 1990 level but could also increase by 15 percent.

Obviously, once the target of global emission reduction is confirmed, the reduction amount of developed nations and the developing world would plunge to a relation of ebb and flow. The demand that developing countries should cut 15-30 percent under their BAU scenarios by 2020, in fact, creates conditions for developed nations to reduce or even escape from undertaking obligations in cutting emissions.

Fourth, China's reduction promise is ambitious no matter what kind of BAU scenario is applied. The BAU scenario is a sort of forecasting of the future based on various assumptions, which should be in line with facts and truly reflect the economic and social development course. China's BAU scenario should be formulated on the basis of the "10th Five-Year Plan (2001-05)" period during which China saw rapid industrialization and urbanization.

Therefore, China's promise of 40-45 percent cuts per unit of GDP is by no means inferior to any commitments made by wealthy nations. Moreover, if the factors of energy structure readjustment and the changing forms of forest and land use are included, China's reduction target would be more significant.