Sentences with phrase «atmosphere fluctuates from year to year»
Not exact matches
One possible explanation is that perhaps oxygen levels during that time period fluctuated greatly creating a «yo yo» atmosphere: Going from oxygenless before 3 billion years ago to oxygenated between 3 billion and 2.75 billion years ago and then back to oxygenless from 2.75 billion to 2.4 billion years ago.
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Samples of gas trapped in ice cores taken from the Greenland and Antarctic ice sheets have enabled scientists to determine that the level of CO2 in the atmosphere has fluctuated between approximately 180 ppm (glacial advance and colder climate in the higher latitudes) and 280 ppm (glacial retreat and warmer climate in the higher latitudes), over the past 400,000 or more years.