A simple line chart visualizes the Keeling Curve data, showing monthly CO2 concentrations over time. The chart uses `d3.scaleTime` and `d3.scaleLinear` to map dates and CO2 values to coordinates, with `d3.line` generating the path and `d3.axisLeft` for the axes. The data is sourced from `@curran/keeling-curve-data`, and the visualization is rendered into an SVG using D3's selection and join patterns.