Effect of climate change on surface ozone over North America, Europe, and East Asia

Abstract

The effect of future climate change on surface ozone over North America, Europe, and East Asia is evaluated using present‐day (2000s) and future (2100s) hourly surface ozone simulated by four global models. Future climate follows RCP8.5, while methane and anthropogenic ozone precursors are fixed at year 2000 levels. Climate change shifts the seasonal surface ozone peak to earlier in the year and increases the amplitude of the annual cycle. Increases in mean summertime and high‐percentile ozone are generally found in polluted environments, while decreases are found in clean environments. We propose that climate change augments the efficiency of precursor emissions to generate surface ozone in polluted regions, thus reducing precursor export to neighboring downwind locations. Even with constant biogenic emissions, climate change causes the largest ozone increases at high percentiles. In most cases, air quality extreme episodes become larger and contain higher ozone levels relative to the rest of the distribution.

Co-occurrence of extremes in surface ozone, particulate matter, and temperature over eastern North America

“…Previous work (24,34,35) has defined O 3 extremes over the 2000-2009 decade in a local climatological manner as the 100 d (∼97.3th percentile) with the highest maximum daily 8-h average (MDA8). This approach enabled clear identification of large-scale multiday pollution episodes consisting of connected, locally extreme daily events that were not readily seen using the US Environmental Protection Agency's (EPA) absolute threshold approach.…”

“…In any case, the extremes often co-occur as a result of their shared underlying drivers, greatly increasing the risks to human health (14). The imperative to understand the co-occurrence of health extremes is driven in part by the recognition that episodes of extreme temperatures (15)(16)(17)(18) and poor air quality (19)(20)(21)(22)(23)(24) may become more frequent, longer lasting, and more intense in a warming climate, in which many climate-driven feedbacks can alter air quality independent of emissions (e.g., 8,10,25,26).…”

“…Here we used the methods developed in previous work (24,34,35) to calculate regularly gridded, daily surface values for O 3 , PM 2.5 , and temperature. These quantities are continuous with real units (parts per billion by molar fraction, micrograms per cubic meter, and degrees Celsius), which allowed us to develop a probability distribution for each grid cell and define extreme events in terms of a return time or frequency (days per year).…”

AerChemMIP: quantifying the effects of chemistry and aerosols in CMIP6

“…ACCMIP combined the results from chemistry-climate models (CCMs) and offline chemistry transport models (CTMs) to quantify the central estimate and range of historical and future ozone and aerosol forcings, air quality, and the contributions of individual ozone precursor emissions. Surface ozone diagnostics in ACCMIP were used to evaluate CCM ability to match current air quality episodes and predict future ones (Schnell et al, 2015(Schnell et al, , 2016. NTCF forcings were diagnosed using a mixture of offline radiative transfer models and double-call diagnostics, whereby a model radiation scheme is called twice, with the second call containing one or all radiative species set to fixed values.…”

“…These sources are likely to be affected by climate change, leading to a variety of feedbacks (Arneth et al, 2010) that to date have only been quantified from a limited number of studies (and models) and thus there is a need for a coordinated set of simulations that allows for a consistent and clean comparison between models. For example, the CMIP5 Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) focusing on chemistry had only three model results that could be used to assess climateair quality links (Schnell et al, 2016).…”