The authors investigate the influence of El Niñ o on midtropospheric CO 2 from the Atmospheric Infrared Sounder (AIRS) and the Model for Ozone and Related Chemical Tracers, version 2 (MOZART-2). AIRS midtropospheric CO 2 data are used to study the temporal and spatial variability of CO 2 in response to El Niñ o. CO 2 differences between the central and western Pacific Ocean correlate well with the Southern Oscillation index. To reveal the temporal and spatial variability of the El Niñ o signal

more »

... n the AIRS midtropospheric CO 2 , a multiple regression method is applied to the CO 2 data from September 2002 to February 2011. There is more (less) midtropospheric CO 2 in the central Pacific and less (more) midtropospheric CO 2 in the western Pacific during El Niñ o (La Niñ a) events. Similar results are seen in the MOZART-2 convolved midtropospheric CO 2 , although the El Niñ o signal in the MOZART-2 is weaker than that in the AIRS data.