Those who attended my dataviz talks have seen a version of the following chart that showed up yesterday on New York Times (link):
This chart shows the fluctuation in Arctic sea ice volume over time.
The dataset is a simple time series but contains a bit of complexity. There are several ways to display this data that helps readers understand the complex structure. This particular chart should be read at two levels: there is a seasonal pattern that is illustrated by the dotted curve, and then there are annual fluctuations around that average seasonal pattern. Each year's curve is off from the average in one way or another.
The 2015 line (black) is hugging the bottom of the envelope of curves, which means the ice volume is at a historic low.
Meanwhile the lines for 2010-2014 (blue) all trace near the bottom of the historic collection of curves.
There are several nice touches on this graphic, such as the ample annotation describing interesting features of the data, the smart use of foreground/background to make comparisons, and the use of countries and states (note the vertical axis labels) to bring alive the measure of coverage volume.
Check out my previous post about this data set.
Also, this post talks about finding real-life anchors to help readers judge size data.
My collection of posts about New York Times graphics.
PS. As Mike S. pointed out to me on Twitter, the measure is "ice cover", not ice volume so I edited the wording above. The language here is tricky because we don't usually talk about the "cover" of a country or state so I am using "coverage". The term "surface area" also makes more sense for describing ice than a country.