Tianjin is the largest coastal city in northern China. In terms of urban population, Tianjin is the fourth largest in China, after Shanghai, Beijing, and Guangzhou. In terms of administrative area population, Tianjin ranks fifth in Mainland China. The walled city of Tianjin was built in 1404. As a treaty port since 1860, Tianjin has been a major seaport and gateway to Beijing. During the Boxer Rebellion the city was the seat of the Tianjin Provisional Government. Under the Qing dynasty and the Republic of China, Tianjin became one of the largest cities in the region. At that time, numerous European-style
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