Future ozone levels could be high enough to cause serious damage to plants and crops, even if emissions of greenhouse gases are reduced, a new study has warned.
Without sufficient reductions in emissions, ozone levels could also pose a risk to human health, researchers said.
By combining projections of climate change, emissions reductions and changes in land use across the US, an international research team estimates that by 2050, cumulative exposure to ozone during the summer will be high enough to damage vegetation.
Although the research findings focus on the impact in the US, they raise wider concerns for global air quality, according to lead researcher Dr Maria Val Martin, from the University of Sheffield's Faculty of Engineering.
"The picture isn't uniform across the US, with some areas seeing much higher surface ozone levels than others. However, our findings show that the emissions reductions we're expecting to achieve won't guarantee air quality on their own, as they will be offset by changes in climate and land use and by an increase in wildfires. This is an issue that will affect all parts of the world, not just the US," Martin said.
Researchers combined data on climate change, land use and emissions to create a picture of air quality across the US in 2050.
The model showed that, if greenhouse gas emissions peak in 2040, then by 2050 surface ozone will remain below levels set to safeguard human health, despite increases in ozone caused by higher temperatures and changes in agriculture and forestation.
If emissions continue to rise until 2100, then some areas of the US will see surface ozone above the safe levels set for human health, researchers said.
When the researchers looked at the cumulative impact of ozone over three months in the summer - a standard growing season - they found that under both scenarios, the surface ozone levels would be high enough to cause damage to plants.
This was particularly because during the summer, there were higher emissions from transport and industry of nitrogen oxides, which react with sunlight to create ozone.
"Ozone affects photosynthesis, causing pigmentation on leaves, stunting growth and reducing yield," said Martin.
The study was published in the journal Atmospheric Chemistry and Physics Discussions.
