The ozone–climate penalty over South America and Africa by 2100
<p>Climate change has the potential to increase surface ozone (<span class="inline-formula">O<sub>3</sub></span>) concentrations, known as the “ozone–climate penalty”, through changes to atmospheric chemistry, transport and dry deposition. In the tropics, the...
| Main Authors: | , , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-09-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/22/12331/2022/acp-22-12331-2022.pdf |
| Summary: | <p>Climate change has the potential to increase surface ozone (<span class="inline-formula">O<sub>3</sub></span>)
concentrations, known as the “ozone–climate penalty”, through changes to
atmospheric chemistry, transport and dry deposition. In the tropics, the
response of surface <span class="inline-formula">O<sub>3</sub></span> to changing climate is relatively
understudied but has important consequences for air pollution and human and
ecosystem health. In this study, we evaluate the change in surface <span class="inline-formula">O<sub>3</sub></span>
due to climate change over South America and Africa using three
state-of-the-art Earth system models that follow the Shared Socioeconomic
Pathway 3-7.0 emission scenario from CMIP6. In order to quantify changes
due to climate change alone, we evaluate the difference between simulations
including climate change and simulations with a fixed present-day climate.
We find that by 2100, models predict an ozone–climate penalty in areas
where <span class="inline-formula">O<sub>3</sub></span> is already predicted to be high due to the impacts of
precursor emissions, namely urban and biomass burning areas, although on
average, models predict a decrease in surface <span class="inline-formula">O<sub>3</sub></span> due to climate change.
We identify a small but robust positive trend in annual mean surface <span class="inline-formula">O<sub>3</sub></span>
over polluted areas. Additionally, during biomass burning seasons, seasonal
mean <span class="inline-formula">O<sub>3</sub></span> concentrations increase by 15 ppb (model range 12 to 18 ppb) in
areas with substantial biomass burning such as the arc of deforestation in
the Amazon. The ozone–climate penalty in polluted areas is shown to be
driven by an increased rate of <span class="inline-formula">O<sub>3</sub></span> chemical production, which is
strongly influenced by <span class="inline-formula">NO<sub><i>x</i></sub></span> concentrations and is therefore specific to the
emission pathway chosen. Multiple linear regression finds the change in <span class="inline-formula">NO<sub><i>x</i></sub></span>
concentration to be a strong predictor of the change in <span class="inline-formula">O<sub>3</sub></span> production, whereas increased isoprene emission rate is positively correlated with
increased <span class="inline-formula">O<sub>3</sub></span> destruction, suggesting <span class="inline-formula">NO<sub><i>x</i></sub></span>-limited conditions over the
majority of tropical Africa and South America. However, models disagree on
the role of climate change in remote, low-<span class="inline-formula">NO<sub><i>x</i></sub></span> regions, partly because of
significant differences in <span class="inline-formula">NO<sub><i>x</i></sub></span> concentrations produced by each model. We
also find that the magnitude and location of the ozone–climate penalty in
the Congo Basin has greater inter-model variation than that in the Amazon, so
further model development and validation are needed to constrain the response
in central Africa. We conclude that if the climate were to change according
to the emission scenario used here, models predict that forested areas in
biomass burning locations and urban populations will be at increasing risk
of high <span class="inline-formula">O<sub>3</sub></span> exposure, irrespective of any direct impacts on <span class="inline-formula">O<sub>3</sub></span>
via the prescribed emission scenario.</p> |
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| ISSN: | 1680-7316 1680-7324 |