New York City under siege. The blue balls represent air pollution that animators from Carbon Visuals say enveloped the city in 2010. Each ball, 10 metres in radius, represents a tonne of carbon dioxide gas produced in the city that year, all piled in one place. Other sequences show the emissions build up after an hour and over one day. Carbon Visuals' creative director Adam Nieman says the technique of concrete visualisation is a useful way of explaining complex environmental data.