Air travel may defy gravity, allowing us earthbound humans to rise above the clouds and move at speeds unimaginable only 100 years ago, but it is far from weightless. This new ad from Plane Stupid, a UK-based organization that aims to curb the amount we fly, even provides an exact figure: 400kg, or about 900 pounds, in greenhouse gasses for every passenger aboard. That's the weight of an adult polar bear.

Warning: The following video is not for the faint of heart. While the falling polar bears aren't real, this is CGI at its most convincing. And if Plane Stupid's figures are correct, real polar bears aren't the only creatures with something to worry about.