The United States and China on the paths and policies to carbon neutrality.

The rapid economic development has highlighted the global climate change problem and carbon dioxide emissions have brought challenges to global climate change. The combined carbon emissions of the United States and China are nearly half of global carbon emissions. These two countries have made great contributions to environmental protection and responded actively to global warming, and set the goal of carbon neutrality. This study takes the United States and China as examples to compare their national paths and policies to achieve carbon neutrality while also analyzing the stage effects of carbon emission reduction in these two countries. This study found that the policy systems in the United States and China are opposites of each other. The United States is a "Bottom to Top" system while China is a "Top to Bottom". The CO2 emission in the United States is currently in the absolute carbon emission reduction period, that is, the reduction of total carbon emissions; while China is in the relative carbon emission reduction period, that is, the reduction of carbon emission intensity. China's transition time from carbon peaking to carbon neutrality is shorter than that of the United States, which is a huge challenge for China because its population is much larger than that of the United States. The results of this research can be used by other countries and regions for supporting carbon reduction policy decision-making and achieving UN sustainable development goals (SDGs).