The UN official said she looks forward to more emissions targets in the coming years, especially those related to coal, a major contributor to the country's carbon dioxide emissions.

"More explicit targets to achieve carbon neutrality will be critical in the coming years, including a total emissions cap and targets for limiting coal consumption. This will be a major part in tackling emissions in China, since coal makes up 56.8 percent of total energy," Trankmann said.

Curbing coal use will not be easy, given how it has an impact on energy security and livelihoods in all countries. But there have been positive signals that will favor the process in China, she said.

The China Coal Association projects that coal consumption, amid rising energy demand, will be capped at 4.2 billion metric tons in 2025, which is close to the current level.

Trankmann said China can achieve its emissions targets by continuing its transformation toward a green economy and redirecting investment. This includes reducing financing for fossil fuels and setting carbon prices in a way that reshapes use.

"The assumption that this will come at the cost of economic growth is false. It will actually cost much more later to adapt to the damage brought by climate change than it will cost to mitigate today. So it makes business sense to act now," she said.

Green sectors are already some of the fastest growing in China, Trankmann said. With one-third of the world's installed wind power and a quarter of its solar capacity, China is at the forefront of advancing low-carbon transportation.

As a leading player in renewables, China can provide useful resources and lessons for developing countries looking to go green, including knowledge-sharing and technology transfers via (developing nations') South-South cooperation, she said.

It is vital that China brings strong environmental awareness to programs and investments in other countries, while supporting partner countries in achieving their goals in the Paris Agreement on climate change, Trankmann said.

Another promising area for international cooperation is sharing China's experience in combining energy and poverty alleviation targets and building home solar systems and small off-grid photovoltaic power plants.