Tropical mid-tropospheric CO2 variability driven by the Madden–Julian oscillation

Carbon dioxide (CO2 ) is the most important anthropogenic greenhouse gas in the present-day climate. Most of the community focuses on its long-term (decadal to centennial) behaviors that are relevant to climate change, but there are relatively few discussions of its higher-frequency forms of variability, and none regarding its subseasonal distribution. In this work, we report a largescale intraseasonal variation in the Atmospheric Infrared Sounder CO2 data in the global tropical region associated with the Madden– Julian oscillation (MJO). The peak-to-peak amplitude of the composite MJO modulation is ∼1 ppmv, with a standard error of the composite mean <0.1 ppmv. The correlation structure between CO2 and rainfall and vertical velocity indicate positive (negative) anomalies in CO2 arise due to upward (downward) large-scale vertical motions in the lower troposphere associated with the MJO. These findings can help elucidate how faster processes can organize, transport, and mix CO2 and provide a robustness test for coupled carbon–climate models.