Ozone levels during the strictest months of the quarantine increased in almost the entire European continent, despite the fact that emissions of the polluting gases that produce it, especially those of nitrogen dioxide, decreased. This was revealed by a study carried out by professors from the Complutense University of Madrid and the Spanish Institute of Geosciences , published last week in the journal ScienceDirect .
The reasons for this apparent contradiction are the high temperatures, low humidity and excessive solar radiation that were experienced in most European countries, except in Spain, during the first months of spring 2020, says Carlos Ordóñez, professor of the Department of Earth Physics and Astrophysics of the Complutense and one of the authors of the work.
Research shows that nitrogen dioxide emissions decreased across the European continent between 5% and 55% compared to the same period last year, while ozone concentrations increased between 5% and 22%, except in Spain, where they fell 7% due to the cold, rain and wind that predominated in the Iberian Peninsula during March and April, the months of the measurement.
Ordóñez tells by phone that the analysis of data from 1,300 air quality stations of the European Environment Agency helps to recognize the close and worrying relationship between global warming and the quality of the air we breathe. “With the study we conclude that reducing nitrogen dioxide emissions is not enough to mitigate ozone concentrations,” says Ordóñez.
Ozone is a secondary pollutant, which is formed from photochemical reactions between three elements: nitrogen oxides, which arises from the burning of fossil fuels; volatile organic compounds, present mainly in agrochemicals, and the rays of sunlight. Ordóñez insists that, if we do not radically change our way of life, in the near future the average temperature of the planet will be increasingly higher and the heat waves stronger, and these changes in the meteorology will increase the concentrations of ozone.
Xavier Querol, an air quality expert and professor at the CSIC, agrees with Ordóñez that the stronger global warming, the more intense the ozone episodes will be. “This situation forces us to reduce nitrogen dioxides and volatile organic compounds much more.” Querol explains that an alternative to mitigate this phenomenon can be to stop traffic when there are very strong heat waves, as is done in Madrid or Barcelona when there is an anticyclonic episode . “If we have a lot of pollution and the heat wave comes, the ozone levels are going to be higher and can generate serious health risks,” adds Querol.
The problems with the increase of this oxidizing gas are many and dangerous. Ozone concentrations near the earth’s surface affect human health, the survival of vegetation, and the sustainability of ecosystems. Ordóñez affirms that ozone is harmful to the cardiovascular system and the respiratory system. “This gas is the second most dangerous pollutant in the air, after suspended particles.”
In fact, a study published in The Lancet in 2017 estimates that high ozone exposure contributed to 254,000 deaths worldwide in 2015. Other research, published in Science Advances in August , goes further and concludes that high ozone concentrations Tropospheric hampers the chemical communication of living beings and impoverishes the soil microorganism communities.
For Ordóñez, one of the most revealing and worrying conclusions of the work is that programs to mitigate nitrogen dioxide emissions, such as Madrid Central, are necessary, but not sufficient to prevent ozone from firing in the heat. “We decided to analyze the months of the quarantine because the entire continent stopped. Travel by car and plane, and industry, which are the main generators of pollutants, had an unprecedented stop. However, ozone levels continued to rise due to global warming. “
“Failure to mitigate climate change could lead to further loss of life and economic loss for decades to come”
Ordóñez’s warnings coincide with the call made by Petteri Taalas, secretary general of the World Meteorological Organization (WMO) during the months of confinement. “The reduction of emissions as a result of the economic crisis caused by the coronavirus is not a substitute for actions against climate change,” said Taalas. He added: “Failure to mitigate climate change could lead to further loss of life and economic loss in the coming decades.”
José Vicente Miró, deputy director of Environmental Quality of the Generalitat Valenciana and an ozone expert, affirms, by telephone, that the behavior of this oxidizing gas is very complex because its formation is not linear. “The most advanced computer models to simulate the creation of ozone use a maximum of 500 different chemical reactions, but more than 13,000 are recorded in the atmosphere.”
The Valencian researcher agrees with Ordóñez that if solar radiation increases and the amount of polluting precursors is maintained, there will be more ozone production. Miró, however, argues that not only can global warming generate more ozone, but ozone can warm the atmosphere. ”Ozone has a warming potential 200 times higher than CO₂, its presence contributes to increasing temperatures on a local, not global scale. For example, in Valencia, the coastline with the highest industrial activity, where more ozone is emitted, behaves like a heat island ”.