Given the task definition and input, reply with output. You need to read the given passage and construct a question about the information present in the passage. The question should be answerable from the passage. Most importantly, only those questions are allowed whose answers cannot be determined from a single sentence. Do not generate questions that require only a single sentence to answer. Instead, try to combine two sentences and create a question from that combination. Do not create open-ended questions, i.e., the answers to them cannot be found precisely from the information provided in the passage.

Paragraph- Sent 1: You may be wondering, how can a glacier get so big?
Sent 2: Why does it move?
Sent 3: These are both good questions.
Sent 4: In the winter months, precipitation falls as snow.
Sent 5: This solid form of water builds up on the ground as long as the temperatures stay cold enough.
Sent 6: As the temperature rises, the snow starts to melt.
Sent 7: The frozen water changes state back into a liquid state.
Sent 8: Nearer the poles, summer does not last very long.
Sent 9: If the summer is long enough and warm enough, all the snow may melt.
Sent 10: This is what typically happens now.
Sent 11: The earth was a little cooler 12,000 years ago.
Sent 12: As a result, during the summer months, that amount of snow did not melt.
Sent 13: It may have only been an inch or so of snow that melted.
Sent 14: The following winter, snow fell on top of this left-over snow.
Sent 15: This next winters snowfall had a head start.
Sent 16: Year after year, the snow that did not melt became thicker and thicker.
Sent 17: Inch by inch the snow started to build up.
Sent 18: Over many years, layer upon layer of snow compacted and turned to ice.
What climate is needed for glaciers to form.?