A study by Wespes et al. (2017) presents global patterns of the main geophysical drivers of IASI O3 variations, obtained by applying appropriate annual and seasonal multivariate regression models on time series of spatially gridded averaged O3. They show that the models are able to explain most of the O3 variability captured by IASI and that they allow identifying clear significant dynamical features (namely NAO, QBO and ENSO) with marked regional differences. They also show that the ENSO perturbs the O3 variability far from the tropics into mid- and high latitudes where a significant 4-month time-lag in the response of O3 to ENSO is identified for the first time.