  Chemical transport models (CTMs) have been widely used to provide
instructions for the control of ozone (O3) pollution. However, we find large
discrepancies between observation- and model-based urban O3 chemical regimes:
volatile organic compound (VOC)-limited regimes over N. China and weak nitrogen
oxides (NOx)-limited regimes over S. China in observations, in contrast to
simulations with widespread distributions of strong NOx-limited regimes. The
conflicting O3 evolutions are caused by underestimated urban NOx concentrations
and the possible overestimation of biogenic VOC emissions. Reductions in NOx
emissions, in response to regulations, have thus led to an unintended
deterioration of O3 pollution over N. China provinces, for example, an increase
in surface O3 by approximately 7 ppb over the Sichuan Basin (SCB) in 2014-2020.
The NOx-induced urban O3 changes resulted in an increase in premature mortality
by approximately 3000 cases in 2015-2020.
