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Leaving ink traces

Stefan S. at the UNEP GEO Data Portal sent me some intriguing charts, made from data about the environment.  The following shows the amount of CO2 emissions by country, both in aggregate and per capita.  We looked at some of their other charts before.


These "inkblot" charts are visually appealing, and have some similarities with word clouds.  It's pretty easy to find the important pieces of data; and while in general we should not sort things alphabetically, here, as in word clouds, the alphabetical order is actually superior as it spaces out the important bits.  If these were sorted by size, we'll end up with all the big blots on top, and a bunch of narrow lines at the bottom - and it will look very ugly.

The chart also breaks another rule. Each inkblot is a mirror image about a horizontal line. This arrangement is akin to arranging a bar chart with the bars centered (this has been done before, here).  It works here because there is no meaningful zero point (put differently, many zero points) on the vertical scale, and the data is encoded in the height of each inkblot at any given time.

Breaking such a rule has an unintended negative.  The change over time within each country is obscured: the slope of the upper envelope now only contains half of the change, the other half exists in the lower envelope's slope.  Given that the more important goal is cross-country comparison, I think the tradeoff is reasonable.


Colors are chosen to help readers shift left and right between the per capita data and the aggregate data.  Gridlines and labels are judicious.

As with other infographics, this chart does well to organize and expose interesting bits of data but doesn't address the next level of questions, such as why some countries contribute more pollution than others.

One suggestion: restrict the countries depicted to satisfy both rules (per capita emissions > 1000 kg AND total emissions > 10 million tonnes).  In this version, a country like Albania is found only on one chart but not the other.  This disrupts the shifting back and forth between the two charts.




Bernard Lebelle


It can be viewed here :














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