If they're right, it could be pretty bad news, even for those who already worry about rising CO2. It's generally agreed that during the earlier warm period, known as the Miocene Climatic Optimum, which occurred 15 million years ago, the global temperature was high enough to make sea levels between 80 ft. and 130 ft. higher than they are today. According to the new study, CO2 levels in the atmosphere at that time hovered at from 390 to 430 parts per million (p.p.m.). Today's CO2 level: 387 p.p.m. and rising."
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