Warming of 3 degrees C, relative to pre-industrial conditions, reached by mid-century could compromise efforts to reduce ozone pollution in Europe, suggests a modelling study published in Nature Communications this week.

Ozone pollution remains an important environmental problem in Europe, but implementation of current air quality legislation is expected to result in considerable reductions of ozone precursor emissions. However, higher temperatures could also enhance ozone pollution.

Audrey Fortems-Cheiney and colleagues use a chemistry transport model to examine the effect of reaching either 2 degrees C or 3 degrees C of warming above pre-industrial levels under different mitigation scenarios on European ozone surface concentrations. The regional model shows that in a specific scenario with no mitigation of greenhouse gas emissions (known as RCP8.5), where 3 degrees C warming is reached sometime between 2040 and 2069, ozone levels are 8% higher compared to a scenario where moderate mitigation is implemented (RCP4.5) and only 2 degrees C warming is reached along the 2028-2057 period. The difference is attributed to higher methane concentrations at Europe’s boundaries in the RCP8.5 scenario, leading to an increase in ozone levels.

This specific modelling study suggests that ozone concentrations reached under a scenario with no mitigation and 3 degrees C warming by mid-century could outweigh reductions brought about by regulating ozone emissions. This finding highlights the need for implementation of regional emissions regulations as well as policies to reduce global methane concentrations. However the authors note that these projections relate to a specific region and climate scenario, and different emission or temperature trajectories may alter the predicted ozone increases.