Global volume of man-made carbon dioxide (CO2). Illustration showing the total volume of CO2 in the Earth's atmosphere, as a column over the United Kingdom (UK). This column consists of a cube (blue) that measures 105 kilometres on each side, representing the natural CO2 levels in 1750. The pink volume (45 kilometres high) represents the CO2 added by humans (anthropogenic CO2 emitted by industrial sources) since then. The CO2 percentages are 70 percent natural and 30 percent man-made. This visualisation was created to mark the moment CO2 levels in the atmosphere reached a value of 400 parts per million on 9 May 2013.