English: The concentration of CO2 measured by AIRS is overlain on measurements of vegetation index from the Moderate Resolution Imaging Spectroradiaometer (MODIS), also on the Aqua spacecraft, in an effort to understand the influence of photosynthesis and respiration on the atmospheric CO2 cycle over the globe. The AIRS tropospheric CO2 seasonal cycle displayed is an average over 8 years of AIRS data, from which the annual growth trend of 2 ppm/year has been removed. The animation shows the buildup of tropospheric CO2 in the Northern Hemisphere with a maximum around May. The maximum in the vegetation cycle follows, occurring in the late summer. Following the peak in vegetation, the drawdown of atmospheric CO2 due to photosynthesis is apparent, particularly over the Boreal Forests.