Tropospheric ozone is influenced by El Niño-Southern Oscillation (ENSO), a climate pattern. ENSO affects ozone levels more over oceans than continents, with stronger impacts in upper and lower troposphere compared to the middle. While ENSO's effect on surface ozone is not well-simulated, it is more consistent in the middle and upper troposphere across models. ENSO has a significant impact on tropospheric ozone in mid-latitude regions over the southern Pacific, Atlantic, and Indian oceans.