BEIJING--As China scrambles to respond to the choking smog that has _ Beijing in recent weeks, authorities in several major cities are experimenting with carbon trading platforms. The schemes are one effort to get control over greenhouse gases in an economy still hungry for cheap energy. It has been a persistent concern in recent years, but the spiking pollution levels in January are sparking a public outcry. Emissions from coal-fired electricity plants and busy factories are part of the problem that officials hope to get control over through carbon trading platforms. Seven cities are expected to open carbon markets later this year, including Tianjin. "The government has decided to start with programs because the carbon trading is something new to China," said David Tang, secretary of the board of the Tianjin Carbon Exchange. "So we want to have a number of programs to explore the use of the market." said Tang. China wants to launch a national carbon trading program by 2016. If it is successful, analysts say, the program would be one of the largest in the world and would help the country meet its target of cutting carbon dioxide emissions by 45 percent within seven years. The platforms allow companies to earn credits for lowering greenhouse gas emissions, which can then be traded. If it works, it would encourage for-profit businesses to invest in green technology. As public concern builds pressure for the government to find a solution, Wu Changhua, greater China director of the Climate Group, says there is a broad shift under way in how Chinese weigh their quality of life. China has long put economic growth ahead of environmental concerns, making it the world's biggest polluter. Carbon trading supporters hope that the markets could be one way to curb pollution and keep the economy growing. Tang's attitude towards carbon markets is   _  .
unknown indifferent optimistic pessimistic