Another Reason to Reduce Man-made Ozone: To Cool a Warming Planet

Benjamin S. Felzer highlights the importance of new research showing that cleaning up ozone precursors within energy, industrial and transportation sectors could mitigate climate change.

In a News and Views article in Nature Climate Change, “Cleaner Air is a Win-Win,” Benjamin S. Felzer, professor of earth and environmental sciences, highlights the importance of a new analysis based on Earth system modelling, showing that cleaning up ozone precursors within specific economic sectors can increase the mitigation potential of the land carbon sink by enhancing the ability of vegetation to remove carbon dioxide from the atmosphere through photosynthesis. (Unger, N., Zheng, Y., Yue, X. & Harper, K. L. Nat. Clim. Change https://doi.org/10.1038/s41558-019-0678-3 (2020)). Global climate models, Felzer notes, indicate that ozone limits photosynthesis and vegetation growth in polluted regions such as the eastern United States, eatern China and Europe which, in turn, limits the ability of these regions to act as carbon sinks.

Felzer writes: “The study [by Nadine Unger et al]...assesses the effect of reducing ozone precursors in seven different economic emission sectors, the most important of which turn out to be energy (electricity and heat production from fossil fuel burning), industry (fossil fuels burned on site), road transportation and agriculture.

Unger et al. ran an Earth system model, linking climate to atmospheric chemistry, to explore the global effects on photosynthesis of reducing emissions from these sectors by 50%. Ozone pollution resulted in 9–13% reductions in photosynthesis in the aforementioned polluted regions. Cleaning up ozone precursors in the transportation, energy, industrial or agricultural sectors led to 13–16% gains in photosynthesis in eastern China, and 16–23% gains in the eastern United States and Europe due to the transportation and energy sectors. Benefits were 2–3 times larger in croplands and grasslands than forests. A 50% reduction in ozone pollution from just the transportation and energy sectors resulted in an increase in photosynthesis equivalent to the amount of carbon lost by fire each year.”
 
According to Felzer, Unger and colleagues ultimately conclude that the mitigation potential resulting from addressing ozone pollution would result in a 15% increase in the size of the current land sink for carbon.