Isolating the modulation of mean warming and higher-order temperature changes on ozone in a changing climate over the contiguous United States

Surface ozone is substantially affected by climate change through the modulation of key meteorological parameters such as temperature. While the changes in temperature under a warming climate manifest in changes of both the mean and higher-order statistical moments, their individual role in ozone concentration changes has not been broadly investigated. To address this gap, we use a novel approach to isolate the impacts of mean warming and changes in higher-order moments of temperature on ozone over the southeastern U.S. (SEUS) and western U.S. (WUS) by the mid-21st century based on simulations under Technology Driver Model A1B and B2 scenarios from a regional modeling framework (Weather Research and Forecasting model coupled with Chemistry (WRF/Chem)). Mean warming generally dominates the impacts of climate change on ozone, and higher-order moment temperature changes can also counteract 25% of the ozone exceedance of 70 ppbv over SEUS, and may offset 48% of the mean warming induced increase of ozone exceedance in heat waves during 2046-2055 under A1B. The opposite changes in the higher-order moments over SEUS and WUS lead to opposite impacts on ozone exceedance in the two regions. Our results suggest that improving prediction of both the mean and higher-order temperature changes may be crucial to constraining the future changes in ozone concentration to better inform air quality policy.

Automated summary

The study reveals that climate change affects surface ozone primarily through the changes in mean warming and higher-order moments of temperature. Mean warming has a significant impact on ozone concentration, while changes in higher-order moments of temperature can partially offset ozone exceedance. The opposite changes in higher-order moments in different regions lead to different impacts on ozone exceedance.