Telecommunications in China pie charts). China's number of Internet users or netizens topped 137 million by the end of 2006, an increase of 23.4% from a year before and 162 million by June 2007, making China the second largest Internet user after the United States. The latest figure (December 2011) have China's internet users exceeding 513 million making it the largest internet user in the world. As of 2004, the largest concentration of Internet users were from Guangdong, Zhejiang, Fujian, Jiangsu, Liaoning, Shandong and Hubei provinces. Beijing, Shanghai and Tianjin also had a high concentration of Internet users, with 28% of Beijing's population
Environmental issues in China cumulative largest. China has ratified the Kyoto Protocol, but as a non-Annex I country is not required to limit greenhouse gas emissions under terms of the agreement. Various forms of pollution have increased as China have industrialized which has caused widespread environmental and health problems. China has responded with increasing environmental regulations and a build-up of pollutant treatment infrastructure which have caused improvements on some variables. As of 2013 Beijing, which lies in a topographic bowl, has significant industry, and heats with coal, is subject to air inversions resulting in extremely high levels of pollution in winter months. In response