Ozone reduction strategies likely to be affected by climate change

A new study has found that climate change is likely to make it harder to control ground-level ozone, which can trigger a variety of health problems among children, the elderly and people with lung diseases such as asthma.

The team from MIT found that as the planet warms, strategies that currently reduce ozone, such as cutting nitrogen oxide (NOx) emissions from vehicles and industry, may become less effective in some regions.

The researchers used advanced computer models to explore how global warming may affect efforts to reduce ozone pollution in three major regions: Eastern North America, Western Europe, and Northeast Asia.

Simulating two future scenarios, one with high warming and one with low warming, over a 16-year period between 2080 and 2095, the team compared them to a historical scenario between 2000 and 2015 to see the effects of a 10% reduction in NOx emissions.

Their results show that as the planet warms, ozone in North America and Europe will become harder to control, requiring steeper cuts in NOₓ emissions to achieve the same air quality improvements. 

This is primarily because warmer temperatures stimulate microbial activity in soil, which releases more NOx.  These NOₓ emissions add to the total pollution load, making it harder to see the benefits of cutting human-made NOₓ emissions (e.g., from vehicles or factories).

In turn, as these natural NOₓ emissions rise, ozone becomes less responsive to reductions in human-caused NOₓ, making traditional control strategies less effective.

By contrast, cutting emissions in Northeast Asia will become more effective at reducing ozone levels in the future due to the region having more intense industrial activity, which emits high levels of NOₓ and VOCs. These emissions have a stronger influence on ozone formation so even as temperatures rise, the ozone remains highly sensitive to emission cuts.

Emmie Le Roy, a graduate student in the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS) and lead author added a qualifier: ‘I wouldn’t say that is a good thing because it means that, overall, there are higher levels of ozone.’