Hi, I'm looking at the chart of N2O concentration in atmosphere. The source is Advanced Global Atmospheric Gases Experiment (AGAGE). They have data from 1978, but the chart shows from year 1750. From where are the data before 1978?<br />Link to chart:<br /><a href="https://www.eea.europa.eu/data-and-maps/daviz/atmospheric-concentration-of-carbon-dioxide-4#tab-chart_5_filters=%7B%22rowFilters%22%3A%7B%7D%3B%22columnFilters%22%3A%7B%22pre_config_polutant%22%3A%5B%22CH4%20" rel="nofollow">https://www.eea.europa.eu/d[&hellip;]_polutant%22%3A%5B%22CH4%20</a>(ppb)%22%5D%7D%7D<br />Link to source AGAGE:<br /><a href="http://agage.eas.gatech.edu/data_archive/data_figures/monthly/pdf/N2O_mm.pdf" rel="nofollow">http://agage.eas.gatech.edu/[&hellip;]/N2O_mm.pdf</a><br />
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