Another important push was the onset of the Little Ice Age, a climatic phenomenon that led to cooler temperatures in the Northern Hemisphere.
另一个重要的推动因素是小冰期的开始，这一气候现象导致北半球气温下降。
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As planes push cloud temperatures past the tipping point at which supercooled water freezes, the aircraft "seed" the clouds with ice particles, the study says.
研究者称，飞机飞行将云温推至临界点以下，为那些过冷的液态水提供了云形成的冰颗粒，使其凝聚冻结。
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These icebergs push out into the 30-mile-long Ilulissat ice Fjord, and then into Disko Bay and eventually the North Atlantic ocean.