这是第四段。today,people are adding more greenhouse gases to the atmosphere。they drive motor vehicles and operate factories that burn fossil fuels for energy.the burning of these fuels releases carbon dioxie into the air .when forests are burnt down ,carbon dioxide is also released into the atmosphere .trees help to remove carbon dioxide through photosynthesis. however,forests are cut down so there are fewer trees left to do this.
我觉得main idea是people are adding more greenhouse gases to the atmosphere，但是我不知道supporting details是什么
