What have been the patterns of climate change throughout the Earth’s history? Did greenhouse gases cause the Earth to warm up after the last ice age?
Scientists using ice cores to measure temperatures and levels of carbon dioxide found evidence of a series of major temperature fluctuations (including ice ages) during the past 400,000 years. These fluctuations have been accompanied by changes in atmospheric levels of carbon dioxide. Scientists think that the largest temperature fluctuations have been triggered by Milankovitch cycles, or variations in the Earth’s orbit that affect the amount of sunlight that reaches us. But these cycles alone are not enough to explain the temperature changes. It seems that the changes caused by variations in the Earth’s orbit were amplified by natural processes on Earth that caused a release of carbon dioxide, enhancing the greenhouse effect. About 20,000 years ago, the Earth saw the end of an ice age. The temperature began to warm, probably because of changes in the Earth’s orbit, and about 11,000 years ago humans began building societies, cultivating food, and domesticating animals, sustained by rel
