This visualization plots the Keeling Curve, showing monthly average and interpolated CO2 concentrations from NOAA’s Mauna Loa records over time. Two line charts trace the raw average and interpolated data against a shared x-axis of decimal dates, with gridlines extending from the axes. The example uses D3’s `scaleLinear`, `line`, `axisBottom`, and `axisLeft` to generate the paths and axes, loading data from `co2_mm_mlo.csv` via `d3.csv`.