Swipe ideas from some of the best Facebook ads
GUILT
Advertiser: ZSL

Guilt and worry are powerful emotions. Couple those emotions with one of the hottest topics around the world - the natural environment - and you've already got yourself a compelling ad.
You could say that this advert from ZSL is jumping on a very emotive bandwagon, but in this instance it's both understandable and justified.
Putting aside personal feelings (I'm ex-Royal Navy so oceanic environmental issues are close to my heart), this ad uses a shocking statistic to highlight the issue. If I was in charge of producing the ad I would have included a picture of a snorkeller or diver in the picture to highlight how humans are responsible for the rising sea temperatures. Any time you can include real people in photos you should, as it creates an emotional attachment we have with fellow humans.