A line chart shows the annual value of CO2 emissions from 1995 to 2014, with each year represented by a white circle with a teal outline. The circles change their stroke to black on hover, and a tooltip displays the exact value for each point. The visualization uses D3 v4 to read the CSV data, build a time-scale X axis and a linear Y axis, and draw a smoothed curve using `d3.line()` with `curveBasis`. The SVG output includes axes, circles, and the path, while the tooltip is appended as an HTML div in the page.