China: NASA satellite images show China as one of the most polluted countries in the world. According to NASA, China has seen a dramatic increase in pollution in the past decade. On Dec. 19, Beijing issued its second red alert for pollution in a month. China, the world's growing manufacturing hub, saw an increase of 20-50 percent in nitrogen dioxide. World Health Organization says nitrogen dioxide is a threat to respiratory health. People in Beijing wear masks for protection. At COP21 meet, governments from 195 countries agreed to keep global warming below 2 degrees Celsius.