NANCHANG -- China's carbon trading market had a total transaction volume of roughly 6.8 billion yuan ($985 million) by end-May, official data showed.

About 310 million tonnes of carbon dioxide emission quotas had been traded, according to the Ministry of Ecology and Environment.

China piloted carbon emission trading in seven provinces and cities in 2011 to explore market-based mechanisms to control greenhouse gas emissions. A national carbon emission trading market was launched in 2017.

China's carbon dioxide emission per GDP dropped by 45.8 percent in 2018 from the 2005 level, a stride toward the goal of meeting the emission peak in about 2030.

Wednesday marked the annual National Low-carbon Day, which falls on the third day of the National Energy Efficiency Promotion Week in June every year.