Carbon dioxide pollution is the primary reason the Earth is warming. It is measured in parts per million. In 1958, the starting point of measuring CO2, it stood at 316ppm. The level of CO2 rises quickly and reaches 403ppm in 2015. Even though CO2 level falls every year between May and October, the carbon level climbs back up after summer and the overall trend is increasing.
Mouse over the lines to see data points and highlight a line.