The concentration of CO2 in the atmosphere is rising, and we have good data on that from, among other sources, atmospheric measurements that have been taken near the summit of Mauna Loa, in Hawaii, for decades.

Here is a link to monthly data through September 2018, as a CODAP document. There’s a clear upward trend.

Each of the 726 dots in the graph represents the average value for one month of data.

What do we have to do—what *data moves* can we make—to make better sense of the data? One thing that any beginning stats person might do is to fit a line to the data. I won’t do that here, but you can imagine what happens: the data curve upward, so the line is a poor model, but the positive slope of the line (about 1.5, which is in ppm per year) is a useful average rate of increase over the interval we’re looking at. You could consider fitting a curve, or a sequence of line segments, but we won’t do that either.

Instead, let’s point out that the swath of points is *wide*. There are lots of overlapping points. We should zoom in and see if there is a pattern.