Dangerous ozone has increased over the past 20 years in the Northern Hemisphere

Tropospheric ozone - ozone between the Earth's surface and 12-15 km above the Earth - is a greenhouse gas

and an air pollutant that, in large quantities, can harm the lungs and adversely affect plants.

A team of scientists found a general increase in ozone levels over the Northern Hemisphere.

We are trying to limit local air pollution and new research shows that this may not work as well as we thought.

Audrey Godel, CIRES Scientist at NOAA's Chemical Science Laboratory and lead author of the study

Scientists have documented the largest increaseozone levels in the tropics, noting that ozone exported from the tropics may increase ozone levels compared to other areas in the Northern Hemisphere.

Also, the researchers found striking growthregions where ozone levels were once lowest, such as Malaysia / Indonesia, Southeast Asia and India. These regions had very low ozone levels from 1994 to 2004 and very high levels from 2011 to 2016.

In previous studies, scientists have failedto draw clear conclusions about ozone growth trends in the Northern Hemisphere because there are too few sites for long-term monitoring. In addition, new satellites with near-global coverage have produced conflicting results on gas trends.

Researchers turned to aircraft data fromEurope Operational Aircraft Program for the Global Observing System (IAGOS). Since 1994, IAGOS has been measuring ozone worldwide with the same instrument on every plane, giving scientists consistent measurements in time and space from the Earth's surface to the upper troposphere.

The researchers used these measurements tocalculating changes in tropospheric ozone from the mid-1990s to 2016 in 11 regions of the Northern Hemisphere. They found a general increase in ozone content across all surveyed regions. Average ozone values ​​have increased by 5% over the decade.

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