From what I have heard, after a few hundred years the ice core layers get paper thin from compression. After that they use techniques such as bouncing lasers off of dust particles, electrical conductivity and other techniques. Analyzing this data, unfortunately, involves a lot of subjectivity and assumptions.
From what I have heard, after a few hundred years the ice core layers get paper thin from compression. After that they use techniques such as bouncing lasers off of dust particles, electrical conductivity and other techniques. Analyzing this data, unfortunately, involves a lot of subjectivity and assumptions
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I’m not familiar with the details but presumably they would take ice core samples from a lot of different places and only publish dates with their corresponding atmospheric levels when they had a lot of samples. so that the number would be an average estimate.