The chart displays atmospheric CO2 concentrations measured at Mauna Loa, Hawaii, from 1958 onward. It uses a line and scatter plot of monthly measurements, showing an overall upward trend. The visualization is built with D3 version 7, using `d3.scaleTime` and `d3.scaleLinear` to map dates and CO2 values. Data is manually parsed from a CSV file, filtering out missing values, and points are colored by station (blue for MLO, red for others).