So often it’s the simple ideas that work best in advertising – and a new billboard for the World Wildlife Fund created by DraftFCB Toronto makes the point rather well.

The ad, cleverly devised to illustrate the idea that “ocean levels are rising faster than ever” – makes use of an awning which, providing it’s sunny, casts a shadow (onto the poster) which rises as the day progresses - thus simulating rising sea levels. Looks great in this time lapse footage – although it is feasible that a passer by might see the poster in the evening and notice the high sea level - only to pass by the next day at lunchtime to find that "sea levels" had, in fact, dropped. Still, it’s clever and we like it.