"My schoolmates labeled me as an environmental protection ambassador and I was really enjoying it," he says.

He was impelled to pursue an environmental protection career when Typhoon Hato hit Macao in 2017.

"I could still remember the streets littered with fallen trees and the cracked windows on the verge of breaking into pieces," Cheng says, adding that it was normal for Macao in the subtropical zone to suffer five to six typhoons a year, but the damage imposed by Typhoon Hato was catastrophic.

"It was the first time that I was aware of the impact of global climate change on our lives," he says.

In 2018, Cheng learned about the Global Environment Program offered by Tsinghua University during a summer camp. The program teaches technical skills in science and engineering, as well as environment-related subjects such as diplomacy, management, economics and law.

It came to his knowledge that environmental protection is closely connected to society and the economy.

"Dealing with global environmental issues asks for technical skills, management and diplomatic law. I believed this program could offer me the necessary skills to contribute to environmental protection, so I enrolled," he says.

In addition to academic studies, Cheng has actively engaged in related events outside the classroom.

He has been involved in community projects to spread awareness and knowledge about low-carbon and eco-friendly lifestyles.

For instance, he is a core member of Genervision House, a Macao-based platform for knowledge sharing and advocacy that promotes the United Nations 17 Sustainable Development Goals.

At the same time, he works with other students to organize environmental campaigns, such as recycling events and cleanup drives at Tsinghua University.

"Through these activities, we hope to inspire action and behavioral changes," he says.

He helped prepare two sessions of Model Climate Change Conference of Parties held by Tsinghua and two sessions of the SDG Hackathon, where he learned from experts in the field and got to know how global cooperation and innovation contribute to the 17 Sustainable Development Goals.

"I realize that environmental problems are not isolated, but are often closely related to economic development and social equity," he says.

"When considering domestic green and low-carbon transformation, it is often necessary to consider the impact on industrial structure and social areas, like employment; when conducting international climate negotiations, we often need to consider different responsibilities among countries and international development."

As Cheng's knowledge grows, he has begun to see the issue from different perspectives.

"I used to feel confused and frustrated about excessive use of disposable plastic bags, but now I would explore how they affect the environmental system, their ecological footprints, possible alternative materials with lower costs and related law enforcement," he says.

In 2020, Cheng visited South Africa, where he looked into the impact of climate change on the poor.

"People living in the downtown areas of the cities were less affected than those in the slums, where malaria and influenza are more likely to prevail," he says. "Therefore, more help should be given to those at a disadvantage, while protecting the environment."

Like Cheng, Zhang Jiaxuan from Shandong province has also been committed to tackling climate change and studying sustainable development.

The 24-year-old took the national college entrance examination, or gaokao, in 2016 when the Paris Agreement was signed.