The Ozone Paradox: A Growing Cost of a Warmer Atmosphere
Mexico City’s air is getting cleaner, but ozone levels near the ground aren’t decreasing as fast as expected. Climate change is partly to blame.
Mexico City grapples with an unusual paradox: Despite significant reductions in primary pollutants, concentrations of ground-level ozone have stalled in recent years. This conundrum, known as the "ozone paradox," involves the interaction of various atmospheric factors, particularly temperature. In high-altitude and topographically complex Mexico City, ozone is formed through photochemical reactions involving precursor pollutants like nitrogen oxides and volatile organic compounds under the influence of sunlight.
Elevated temperatures accelerate the chemical efficiency of this formation process, leading to higher ozone levels. This relationship between temperature and ozone formation was evident during the COVID-19 lockdown, when emissions dropped but ozone levels remained stubbornly high due to the favorable conditions of reduced NO x emissions, increased sunlight, and higher temperatures.
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