A high concentration CO pool over the Indo-Pacific Warm Pool.

Anthropogenic emissions have produced significant amount of carbon dioxide (CO) in the atmosphere since the beginning of the industrial revolution. High levels of atmospheric CO increases global temperature as CO absorbs outgoing longwave radiation and re-emits. Though a well-mixed greenhouse gas, CO concentration is not uniform in the atmosphere across different altitudes and latitudes. Here, we uncover a region of high CO concentration (i.e. CO pool) in the middle troposphere (500-300 hPa) over the Indo-Pacific Warm Pool (IPWP, 40° E-140° W, 25° S-25° N), in which the CO concentration is higher than that of other regions in the same latitude band (20° N-20° S), by using CO satellite measurements for the period 2002-2017. This CO pool extends from the western Pacific to the eastern Indian Ocean. Much of the CO pool is over the western Pacific Ocean (74.87%), and the remaining lies over the eastern Indian Ocean (25.13%). The rising branch of Walker circulation acts as a "CO Chimney" that constantly transports CO released from the natural, human-induced and ocean outgassing processes to the middle and upper troposphere. The CO pool evolves throughout the year with an average annual trend of about 2.17 ppm yr, as estimated for the period 2003-2016. Our analysis further reveals that La Niña (El Niño) events strengthen (weaken) the CO pool in the mid-troposphere. The radiative forcing for the CO pool suggests more warming in the region and is a grave concern for global warming and climate change.