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. 

Example input:  Magma rises from deep in the earth. The magma goes into volcanos. The volcanos pressure the magma upwards. The pressure causes the magma to push through the surface of the volcano. The lava cools. The lava forms new rock. New magma is pressured to the surface of the volcano. The volcano bursts through the rock the formed after the last eruption. 
Example output:  magma ,lava ,new rock 
Example explanation: The entities are present in the process paragraph and they undergo state change. So, this is a positive example.
Q: Greenhouse gases are released into the air by human activities. The earth changes energy from the sun into heat. Heat rises from the ground. Greenhouse gas molecules in the atmosphere prevent the heat from going into space. The temperature of the earth increases. The temperature continues to rise and melts the polar ice caps. The temperature rises even faster. 
A:
greenhouse gas ,air ,earth ,energy from sun ,heat ,greenhouse gas molecules ,polar ice cap 