Graphing Out Loud: curves and lines

I love graphs – my eyes quickly glaze over at a table of numeric data, but a graph, used correctly, can quickly and easily tell the whole story.

‘Used correctly’ is the key phrase – for all their power, graphs are infamously easy to bungle, and when used incorrectly they can misinform – or lie outright.

I’m going to look at an example that touches on a few graphical and statistical concepts near and dear to my heart, as well as carbon geochemistry.

Fig. 1: An image from C3Headlines; the 3 C's are "Climate, Conservative, Consumer". Oh, and the article is titled "The Left/Liberal Bizarro, Anti-Science Hyperbole Continues". It sure would be tragic if they made obvious n00b mistakes after using such language. Click for link!

Coming from an article on the website C3Headlines, this image claims that carbon dioxide concentrations have ‘Linear, Not Exponential Growth’. thereby ‘expos[ing] the lunacy of typical left/liberal/progressive/Democrat anti-science’, The author has reached this conclusion by graphing January CO2 levels* and fitting a linear trendline to them.

Already this is a warning sign – the comparisons the author makes are entirely qualitative, apparently  based up on eyeballing the graph. However, trend lines are created by a statistical process called a linear regression, which comes with a caveat: it will fit a trend line to ANY data given to it, linear or nonlinear. Fortunately, there are also ways of evaluating how good a trend line is.

John Everett part III.3 : … and they get the last word again!

A part of my John Everett series – read more: 0/I - II.0 - II.5 - II.75 -  III.0 - III.3 - IV.0 - IV.4 - IV.8 - V - VII - VIII - Full Report 

Often, in order to explain why a particular Weird Belief is correct despite being at odds with available evidence, the belief holder will invoke conspiracy theories. Young Earth Creationists often invoke a conspiracy by god and/or satan to make the earth look much older than it actually is. Intelligent Design Creationists allege an academic conspiracy to suppress ID research. Climate change skuptiks see conspiracies to falsify data the way I see faces in clouds. It’s not necessarily that conspiracies don’t exist- but because the point of a conspiracy is to mask its own existence, we have to be very careful in deciding which conspiracy theories are justified and which aren’t.

Dr. Everett doesn’t invoke a conspiracy in the classical sense of a bunch of men in suits, smoking cigars in a dimly lit room. But he does seem to invoke a distributed, systemic conspiracy, in which science as a system has been corrupted, and its results can not be trusted. He does this in order to cast doubt on studies of the effects of acidification on calcifiers: