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.

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.
fossil fuels ,carbon dioxide ,trees

The piston starts at the top, the intake valve opens, and the piston moves down to let the engine take in a cylinder-full of air and gasoline. Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful. When the piston reaches the top of its stroke, the spark plug emits a spark to ignite the gasoline. The gasoline charge in the cylinder explodes, driving the piston down. Once the piston hits the bottom of its stroke, the exhaust valve opens and the exhaust leaves the cylinder to go out the tailpipe.
piston ,air ,gasoline ,spark ,explosion ,exhaust

You start with a glacier. Through warming or other methods a chunk is taken off the glacier. The chunk drifts into the sea. And it settles where it can remain in its state. It is considered an iceberg.
Glacier ,Chunk ,iceberg