Global carbon dioxide levels from 2002 to 2009. Earth map animation cylindrical projection showing the worldwide variation and rise in carbon dioxide levels in the Earth磗 atmosphere from September 2002 to December 2009. The month and year are given at lower left during the sequence. This data mid_tropospheric levels is from the Atmospheric Infrared Sounder AIRS instrument on NASA磗 Aqua satellite. The levels of carbon dioxide are color_coded key at lower right, ranging from 364 parts per million blue through light blue, green, yellow and orange, to 395 parts per million red. The sequence shows the seasonal variation due to the growth cycle of plants, as well as the overall increase of around 2 parts per million ppm per year. The seasonal variation is more pronounced in the northern hemisphere. Carbon dioxide is a greenhouse gas that contributes to global warming and climate change.