drilling down beneath a lake in alaska yields chemical evidence of past changes in climate. biological silicon, left by the skeletons of single celled creatures called diatoms, is a measure of the abundance of life in the lake. a rather complex variable based on the ratio of certain isotopes relative to ocean water gives an indirect measure of moisture, mostly from snow. as we drill down, we look further into the past, here is a scatterplot of data from 2300 to 12000 years ago
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