Which is the Correct Graph for Carbon Dioxide Concentrations in the Atmosphere?
The following are three graphs representing the change in parts per million of carbon dioxide (CO2) measured at the Mauna Loa Observatory in Hawaii from March 1958 through December 2015:
All three graphs accurately represent the same data. Each is presented on a different scale. The first graph takes the upper and lower bounds of the period 1958-2015 as the appropriate Y-axis scale. This is the approach to CO2 concentration graphing taken by NOAA. The second graph features the same maximum, but offers the value 0 as a minimum for the Y-axis. The third graph puts 2,000 parts per million of CO2 as the upper limit of the axis, based on the apparent maximum CO2 concentration level between the current day and the ancient Triassic period when dinosaurs roamed the planet.
Which of the three Y-axis configurations is most appropriate, in your opinion? Why? What does that graph demonstrate that the others don’t?