A fantastic example of how to strip meaning from a graph this week, in this little beauty from Christopher Booker in the Telegraph.
“Look at the graph” he says “to see the evidence of global warming”. Just look at it.
Pretty unimpressive, eh?
Regular readers won’t really need me to point out just how silly plotting a short term temperature record against an arbitrary temperature value is (even while claiming it isn’t arbitrary!). We at better figures wonder how Mr Booker missed the opportunity to plot it against absolute zero?
In the spirit of the graph, let’s do a thought experiment. What if we had some amazing machine, that were able to instantaneously melt Antarctica? That would have a pretty dramatic effect on sea level, wouldn’t it? Certainly at least an order of magnitude larger than the projections that the IPCC has made in the past, or what the current scientific thinking might suggest.
Let’s make a plot. Thanks to this (rather nicely illustrated) story on the beeb last week, we know that the biggest ice cube on the planet is worth around 58 metres of sea level rise. Wikipedia links to a paper that has the mean depth of the ocean at 3,682 metres. So, what would happen to the sea level, if we took that colossal amount of freshwater, and put it in the ocean in 2050?
So, nothing to worry about, right. Except for, er, swamping a significant proportion of the planet’s coastal cities*.
OK, so we’ve probably missed some pretty important details, but still, I hope this illustrates the point. We should be placing changes in temperature in historical context, and showing what they mean for the people and systems that experience them. We shouldn’t be stripping the meaning out of the numbers.
Here is some good advice from Edward Tufte:
“The urge to contextualize the data is a good one, but context does not come from empty vertical space reaching down to zero, a number which does not even occur in a good many data sets. Instead, for context, show more data horizontally!”
* We’d like to point out that a 58 metre rise in sea level is not going to happen on a timescale that humans are capable of thinking about.