“`html
Climate change is expected to obstruct our future capacity to manage ground-level ozone, a detrimental air contaminant that constitutes a major element of smog, according to a recent MIT research.
The findings could assist scientists and decision-makers in formulating more efficient strategies for enhancing both air quality and public health. Ground-level ozone leads to a variety of adverse health effects, ranging from asthma to cardiovascular issues, and contributes to numerous premature fatalities annually.
The researchers’ modeling strategy indicates that as the planet heats up because of climate change, ground-level ozone will become less responsive to decreases in nitrogen oxide emissions in eastern North America and Western Europe. In simpler terms, more substantial reductions in nitrogen oxide emissions will be necessary to achieve the same air quality improvements.
Conversely, the study also indicates that this would not apply to northeast Asia, where reducing emissions will have a greater effect on diminishing ground-level ozone in the future.
The researchers integrated a climate model that simulates weather conditions, such as temperature and wind speeds, with a chemical transport model that estimates the movement and composition of atmospheric chemicals.
By generating a spectrum of potential future scenarios, the researchers’ ensemble method more accurately captures inherent climate fluctuations, enabling them to provide a broader perspective than many previous analyses.
“Future air quality strategies should take into account how climate change influences the chemistry of air pollution. We may require larger reductions in nitrogen oxide emissions to reach the same air quality targets,” states Emmie Le Roy, a graduate student in the MIT Department of Earth, Atmospheric and Planetary Sciences (EAPS) and principal author of a paper regarding this research.
Her co-authors include Anthony Y.H. Wong, a postdoctoral researcher in the MIT Center for Sustainability Science and Strategy; Sebastian D. Eastham, lead research scientist in the MIT Center for Sustainability Science and Strategy; Arlene Fiore, the Peter H. Stone and Paola Malanotte Stone Professor of EAPS; and senior author Noelle Selin, a professor in the Institute for Data, Systems, and Society (IDSS) as well as EAPS. The research is published today in Environmental Science and Technology.
Managing ozone
Ground-level ozone is distinct from the stratospheric ozone layer that shields the Earth from damaging UV radiation. It acts as a respiratory irritant that poses risks to the health of humans, animals, and vegetation.
Managing ground-level ozone is especially complex because it is a secondary pollutant, generated in the atmosphere through intricate reactions involving nitrogen oxides and volatile organic compounds under sunlight.
“This is why you often see elevated ozone levels on warm and sunny days,” Le Roy clarifies.
Regulators typically aim to lower ground-level ozone by decreasing nitrogen oxide emissions from industrial activities. However, predicting the outcomes of these policies is challenging because ground-level ozone interacts with nitrogen oxide and volatile organic compounds in nonlinear fashions.
Based on the chemical context, cutting nitrogen oxide emissions might inadvertently cause an increase in ground-level ozone.
“Previous studies have primarily concentrated on the emissions’ role in ozone formation, but the influence of meteorological factors is a critical aspect of Emmie’s research,” Selin notes.
To execute their study, the researchers combined a global atmospheric chemistry model with a climate model that simulates future weather conditions.
They utilized the climate model to produce meteorological data for each future year in their analysis, simulating aspects like temperature and wind speeds while capturing the innate variability of a region’s climate.
Subsequently, these inputs were provided to the atmospheric chemistry model, which calculates potential changes in atmospheric composition due to weather and emissions.
The researchers specifically focused on Eastern North America, Western Europe, and Northeast China, as these areas have historically experienced elevated levels of chemical precursors that create ozone and possess well-established monitoring networks to gather data.
They opted to model two future scenarios, one anticipating high warming and another predicting low warming, over a 16-year span between 2080 and 2095. They compared these with a historical scenario from 2000 to 2015 to evaluate the effects of a 10 percent reduction in nitrogen oxide emissions.
Accounting for climate variability
“The greatest challenge lies in the fact that climate naturally fluctuates from year to year. To isolate the effects of climate change, one must simulate enough years to move beyond that natural variability,” Le Roy mentions.
They could meet this challenge thanks to recent advancements in atmospheric chemistry modeling and by utilizing parallel computing, allowing them to simulate multiple years simultaneously. They generated five 16-year realizations, resulting in 80 model years for each scenario.
The researchers discovered that eastern North America and Western Europe are particularly sensitive to increases in nitrogen oxide emissions from the soil, which are natural emissions stimulated by rising temperatures.
This sensitivity means that as the planet warms and more nitrogen oxide from soil enters the atmosphere, curtailing nitrogen oxide emissions from human activities will have a diminished impact on ground-level ozone.
“This emphasizes the necessity of enhancing our representation of the biosphere in these models to better understand how climate change might affect air quality,” Le Roy asserts.
Conversely, since industrial processes in northeast Asia generate more ozone per unit of nitrogen oxide emitted, reducing emissions in that region would lead to more significant reductions in ground-level ozone amid future warming scenarios.
“However, I wouldn’t classify that as a positive development, as it suggests that, overall, ozone levels are elevated,” Le Roy adds.
Conducting detailed meteorology simulations, rather than relying on annual average climate data, provided the researchers with a more comprehensive understanding of the potential implications for human health.
“Average climate is not the sole factor of importance. A single high ozone day, which might be a statistical aberration, could result in failing to meet our air quality targets and lead to adverse human health consequences that we should prioritize,” Le Roy states.
Looking ahead, the researchers aim to further investigate the intersection between meteorology and air quality. They also plan to broaden their modeling approach to include other climate change factors characterized by high variability, such as wildfires or biomass burning.
“We have demonstrated that it is critical for air quality scientists to take into consideration the full spectrum of climate variability, even though it may be challenging to incorporate into models, because it genuinely affects the results obtained,” says Selin.
This research is partially financed by the MIT Praecis Presidential Fellowship, the J.H. and E.V. Wade Fellowship, and the MIT Martin Family Society of Fellows for Sustainability.
“`