Meridional propagation of carbon dioxide (CO2) growth rate and flux anomalies from the tropics due to ENSO

El Niño Southern Oscillation (ENSO) influence on carbon dioxide (CO2) growth rates are not spatially uniform or simultaneous around the globe. Using atmospheric CO2 observations and  atmospheric chemistry-transport model (ACTM), we show that the anomalies in CO2 fluxes  and growth rate originate in the tropics, as an effect of ENSO. The CO2 anomalies are then  propagated from the equator toward the poles with asymmetric delays. A maximum delay of  about 8 and 4 months are found at the northern hemisphere (NH) and southern hemisphere  (SH) high latitudes, respectively. This asymmetric time delay is because the CO2 flux anomaly  mainly originate in the tropical SH land and transport of SH air into the NH is slower than that  for NH air into the SH. The poleward increase of time delay is more homogeneous in the upper  troposphere, as per the ACTM simulations, but observational evidence suffers from gaps in 
long-term measurements.