Ozone trends and their sensitivity in global megacities under the warming climate.
Where this comes from
- Record sourced from PubMed, PMID 39592683.
- Also identified by DOI 10.1038/s41467-024-54490-w and PMC identifier 11599728.
- Licence recorded as CC BY-NC-ND.
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Abstract
Tropospheric ozone formation depends on the emissions of volatile organic compounds (VOC) and nitrogen oxides (NO<sub>x</sub>). In megacities, abundant VOC and NO<sub>x</sub> sources cause relentlessly high ozone episodes, affecting a large share of the global population. This study uses data from the Ozone Monitoring Instrument for formaldehyde (HCHO) and nitrogen dioxide (NO<sub>2</sub>) as proxy data for VOC and NO<sub>x</sub> emissions, respectively, with their ratio serving as an indicator of ozone sensitivity. Ground-level ozone (O<sub>3</sub>) reanalysis from the Copernicus Atmosphere Monitoring is used to assess the O<sub>3</sub> trends. We evaluate changes from 2005 to 2019 and their relationship with the warming environment in 41 megacities worldwide, applying seasonal Mann-Kendall, trend decomposition methods, and Pearson correlation analysis. We reveal significant increases in global HCHO (0.1 to 0.31 × 10<sup>15</sup> mol cm<sup>-2</sup> year<sup>-1</sup>) and regionally varying NO<sub>2</sub> (-0.22 to 0.07 × 10<sup>15</sup> mol cm<sup>-2</sup> year<sup>-1</sup>). O<sub>3</sub> trends range from -0.31 to 0.70 ppb year<sup>-1</sup>, highlighting the relevance of precursor abundance on O<sub>3</sub> levels. The strong correlation between precursor emissions and increasing temperature suggests that O<sub>3</sub> will continue to rise as climate change persists.