By combining projections of climate change, emissions reductions and changes in land use across the USA, an international research team has estimated that exposure to ozone during the summer will be high enough to damage vegetation by 2050.

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Although the research findings, published this week, focus on the impact in North America, experts behind the research (including a team from the University of Sheffield), said their findings raise wider concerns for global air quality.

Lead researcher Dr Maria Val Martin said, "Modelling future air quality is very complex, because so many factors need to be taken into account at both a global and local scale. The picture isn't uniform across the USA, 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 USA."

The research looked at air quality under two scenarios set out by the Intergovernmental Panel on Climate Change (IPCC): one which envisages greenhouse gas emissions peaking in 2040 and then falling, the other in which emissions continue to rise until 2100. The team combined data on climate change, land use and emissions to create a picture of air quality across the USA in 30 years' time.

They estimate 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 USA will see surface ozone above these 'safe' levels.

However, the researchers warned that the cumulative impact of ozone over three months in the summer - a standard growing season – would be high enough to damage plants. Higher nitrous oxide emissions from transport and industry over the summer months, which react with sunlight to create ozone, would be the main culprits for the increased levels of pollution.

"Ozone affects photosynthesis, causing pigmentation on leaves, stunting growth and reducing yield," Dr Val Martin explained. "At a time when the world will need to be feeding a growing population, we need to be sure that our ability to do this isn't compromised by surface ozone. Our model shows that we may need more stringent controls of certain emissions - such as nitrogen oxides or methane - that contribute to ozone levels."

Earlier in the month, the IPCC released its Synthesis Report. The report drew together and updated the findings of 800 experts and hundreds of other supporting researchers and reviewers form across the world, who have contributed to the "most comprehensive assessment of climate change ever undertaken." These experts, organised into IPCC's Working Groups, concluded that humanity's effect on the climate is apparent in changes and extreme events happening now and that only immediate and radical action can avoid the worst impacts of changes wrought by pollution and compounded by years of inaction.