Produced by artist Nathan Martell, the shape is based on this graph showing average world temperatures over the last 150 years:
The apocalypse as art. Eat your heart out, Albrecht Dürer.
On a related note, people like Andrew Bolt are fond of showing only the last few lines of this particular graph, dominated by the El Nino peak in 1998, and claiming that warming has stopped.
If you find someone who insists on doing that, smack their fingers out of their ears, force their eyes open, and show them the whole thing.
