The ozone level in the troposphere has been increasing for 20 years. This is not good news

Ozone pollution levels in the Northern Hemisphere have increased over the past 20 years. This is demonstrated by data collected in the atmosphere by commercial aircraft.

In this latest study, scientists at the CIRES Institute at Colorado University at Boulder analyzed ozone levels, a greenhouse gas polluting the low atmosphere of the Earth's northern hemisphere (quite different from the ozone layer much higher above the Earth).

After analyzing data collected by commercial passenger airliners, researchers found that ozone levels in the atmosphere were very low between 1994 and 2004, and then increased to very high levels between 2011 and 2016.

These rising ozone levels are very important news. Although we are trying to reduce the amount of pollution locally, these actions are not as effective as we hoped

Says lead author Audrey Gaudel of CIRES.

62,088 flights over 10 years

Researchers focused on ozone levels in the Northern Hemisphere, as this is where the vast majority of people who are affected by air quality live. As ozone is a greenhouse gas, it also has a direct impact on the climate.

Earlier studies of ozone did not allow scientists to fully understand trends in the Northern Hemisphere due to a lack of monitoring stations and conflicting satellite data.

In our previous international Troposhperic Ozone Assessment Report project, we concluded that satellite measurements do not agree with each other on the evolution of ozone in the troposphere: we have not been able to determine whether the amount of ozone has increased or decreased globally over the decade. This is worrying given the impact ozone has on the climate, health and vegetation

Gaudel adds.

To deal with this problem, scientists took a novel approach to the subject and based their research on data collected by commercial aircraft as part of the IAGOS (In-Service Aircraft for the Global Observing System) program. Although planes collect data locally, if enough planes collect the data, it is possible to create a global picture of the situation, says Gaudel.

Since 1994, IAGOS has measured ozone around the world using the same instruments on every plane, making it possible to make continuous measurements in time and space from the surface to the upper troposphere. Researchers looked at data collected in the troposphere from 11 different locations in the Northern Hemisphere. Over the decade, 34,600 ozone profiles were collected there.

Based on these data, it turned out that the median ozone levels are growing at a rate of 5%. for a decade. Additionally, while ozone levels have decreased at mid-latitudes, where the troposphere is low, where the troposphere is higher, also increases in ozone levels have been higher.

So where does this steady increase in ozone in the atmosphere come from?

Man-made pollution is responsible for this. When researchers looked at the levels of nitrogen oxides (NOx) in the atmosphere, a compound often created with the participation of humans (factories, automotive), it turned out that where the amount of NOx emissions increases, the amount of ozone accumulating in the atmosphere increases. Now Gaudel and his team plan to focus on studying ozone levels in the tropics and its origins. The aim of such research is to understand the diversity of ozone and its sources, and the impact of polluted regions on others.

The ozone level in the troposphere has been increasing for 20 years. This is not good news