Global warming

Im wondering y people dun give any comment on my, is that too much word to understand it? Its an ambient ad with messages on a real door met to ask the traveler reduce their carbon footprint. it show different size of footprint and will be sticked on the ground by the parking machine, airport, train station and bus stop. people will step on it when they are waiting.

Too literal in my opinion. And has many problems.
Firstly, you don't have to show a footprint, to represent a carbon footprint.
Secondly, I don't think many people are familiar with that term. I wasn't, until I googled it.
I advice you to forget about that word. It's limiting your imagination.
And finally, you're not really convincing when you say "save your flight".
Are you suggesting people to swim? :)

Practical considerations:

-- in high traffic areas, no one is going to see this. People in transit spaces arent looking down; they're looking up -- at ticket machines, at schedules, at bus/train numbers. So you're working against something right there.

-- This is an item that I can guarantee would be stolen within the first 24 hours (no, make that 12) of installation.