Snow and ice reflect a lot of the sunlight they receive. Some parts of the Antarctic reflect as much as 90% of the incoming sunlight, compared to a global average of 31%. Without the cryosphere, this planetary average reflectivity would be considerably lower, and more energy would be absorbed at the Earth�s surface, raising its temperature and that of the atmosphere in contact with it. Scientists know that during the age of the dinosaurs 100 million years ago, little or no snow and ice covered the Earth, even at the poles, and the global average temperature was at least 8 to 10?C warmer than today.