Teacher:In this task, you are given a paragraph, and your job is to generate comma-separated entities present in the given paragraph. Generate entities from a given passage in such a way that (i) they are present in the paragraph, (ii) they are non-duplicate, (iii) they underwent a state change during the process. Avoid creating entities that (i) aren't present in the process paragraph and (ii) aren't significant. 
Teacher: Now, understand the problem? Solve this instance: Human beings burn fossil fuels (oil, gas, etc.). Carbon dioxide from the burning fossil fuels enter the atmosphere. The make-up of the atmosphere changes. Some energy from the sun cannot escape back through the changed atmosphere. The earth begins to heat because of the extra trapped energy. Human beings cut down trees. Human beings do not re-plant the trees. Trees cannot help take the extra carbon dioxide from the atmosphere. The extra trapped energy starts to change the earth's short term weather. Eventually the long-term climate patterns start to change. 
Student:
fossil fuels ,carbon dioxide ,trees 