Nav: Home

Ozone across northern hemisphere increased over past 20 years

August 21, 2020

In a first-ever study using ozone data collected by commercial aircraft, researchers from the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder found that levels of the pollutant in the lowest part of Earth's atmosphere have increased across the Northern Hemisphere over the past 20 years. That's even as tighter controls on emissions of ozone precursors have lowered ground-level ozone in some places, including North America and Europe.

Tropospheric ozone--ozone between Earth's surface and 12 to 15 kilometers above Earth--is a greenhouse gas and air pollutant that, at high levels, can harm people's lungs and damage plants.

In a study published today in the journal Science Advances, the team found an overall increase in ozone levels above the Northern Hemisphere. "That's a big deal because it means that as we try to limit our pollution locally, it might not work as well as we thought," said Audrey Gaudel, a CIRES scientist working in the NOAA Chemical Sciences Laboratory and the study's lead author. She and her colleagues documented the greatest ozone increases in the tropics, Gaudel said, noting that ozone exported from the tropics may be driving increases above other areas of the Northern Hemisphere.

Gaudel and her co-authors, CIRES scientists in NOAA and international colleagues, also found the most striking increases in areas where ozone levels were once lowest: Malaysia/Indonesia, Southeast Asia and India, for example. Those regions had very low ozone values between 1994-2004, and very high levels in recent years, between 2011-2016.

Previous studies could not draw firm conclusions on Northern Hemisphere ozone trends, according to Gaudel, because there are too few long-term monitoring locations and because new satellites with near-global coverage have provided conflicting results on ozone trends.

So the researchers turned to aircraft data from Europe's In-Service Aircraft for the Global Observing System (IAGOS) program. "Since 1994, IAGOS has measured ozone worldwide using the same instrument on every plane, giving us consistent measurements over time and space from Earth's surface to the upper troposphere," Gaudel said. Between 1994 and 2016, commercial aircraft captured 34,600 ozone profiles, or about four profiles each day.

Gaudel and her colleagues used these measurements to calculate changes in tropospheric ozone from the mid-1990s to 2016 above 11 regions in the Northern Hemisphere. They found an overall increase in ozone in all regions where they looked, including four in the mid-latitudes, two in the subtropics, two in the tropics and three equatorial regions. On average, median ozone values had increased by 5% per decade.

In the so-called "lower troposphere," which is closer to Earth's surface, ozone has decreased above some mid-latitude regions, including Europe and the United States, where ozone precursor emissions have decreased. The researchers found those reductions were offset by increases higher in the troposphere--with the net result being an overall ozone increase from the surface to 12 km.

To understand what was causing the observed ozone changes, the researchers looked at the emissions inventories of one of the main ozone precursors--nitrogen oxides (NOx)--used as input for the global chemistry transport model MERRA-2 GMI, which reproduces accurately the IAGOS measurements. The model showed that increased anthropogenic emissions in the tropics were likely driving the observed increase of ozone in the Northern Hemisphere.

Next, Gaudel wants to take a closer look at ozone in the tropics. Africa may be emerging as a global hotspot for air pollution precursors, for example, and IAGOS data will let her dig deeper into that continent's role in recent trends. She'll also compare tropical ozone measurements from IAGOS, taken above polluted regions, with measurements from the NASA Atmospheric Tomography (ATom) field campaign, which measured trace gases and aerosol particles in more remote, less polluted regions including the tropics. And she'll look at measurements from TROPOMI, an instrument on board a European Space Agency satellite gathering information on atmospheric composition.

"We want to understand the variability of ozone and its precursors and the impact of polluted regions on remote regions," Gaudel said. "So we're using the best tools we have, including IAGOS, ATom data and TROPOMI data, to get profiles and columns of ozone and its precursors from different kinds of human activities and natural sources."
Authors of "Aircraft observations since the 1990s reveal increases of tropospheric ozone at multiple locations across the Northern Hemisphere" in Science Advances are Audrey Gaudel, Owen R. Cooper, Kai-Lan Chang and Ilann Bourgeois from CIRES and NOAA's Chemical Sciences Laboratory; Jerry R. Ziemke from NASA Goddard Space Flight Center and Morgan State University; Sarah A. Strode from NASA Goddard Space Flight Center and Universities Space Research Association; Luke D. Oman from NASA Goddard Space Flight Center; Pasquale Sellitto from Université de Paris, Institut Pierre Simon Laplace; Philippe Nedelec, Romain Blot and Valerie Thouret from Université de Toulouse, CNRS, UPS; and Claire Granier from CIRES, NOAA's Chemical Sciences Laboratory and Université de Toulouse, CNRS, UPS.

Funder: Authors Audrey Gaudel, Owen R. Cooper, Kai-Lan Chang, and Ilann Bourgeois are supported by the Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder. Authors Valerie Thouret, Philippe Nedelec, Romain Blot are supported by IAGOS which receives funding the European commission, national research programmes in Germany (BMBF), France (INSU-CNRS, MESR, CNES) and UK (NERC).

The MERRA-2 GMI simulation was funded by the NASA MAP program. S.A.S. was supported by the NASA MAP and ACMAP programs. In its last 10 years of operation, MOZAIC was funded by INSU-CNRS (France), Me?te?o-France, Universite? Paul Sabatier (Toulouse, France), and Research Center Ju?lich (FZJ, Ju?lich, Germany). IAGOS has been additionally funded by the EU projects IAGOS-DS and IAGOS-ERI. The MOZAIC-IAGOS database was supported by AERIS (CNES and INSU-CNRS).

University of Colorado at Boulder

Related Ozone Articles:

Investigating the causes of the ozone levels in the Valderejo Nature Reserve
The UPV/EHU's Atmospheric Research Group (GIA) has presented a database comprising over 60 volatile organic compounds (VOC) measured continuously over the last ten years in the Valderejo Nature Reserve (Álava, Basque Country).
FSU Research: Despite less ozone pollution, not all plants benefit
Policies and new technologies have reduced emissions of precursor gases that lead to ozone air pollution, but despite those improvements, the amount of ozone that plants are taking in has not followed the same trend, according to Florida State University researchers.
Iodine may slow ozone layer recovery
Air pollution and iodine from the ocean contribute to damage of Earth's ozone layer.
Ozone threat from climate change
We know the recent extreme heat is something that we can expect more of as a result of increasing temperatures due to climate change.
Super volcanic eruptions interrupt ozone recovery
Strong volcanic eruptions, especially when a super volcano erupts, will have a strong impact on ozone, and might interrupt the ozone recovery processes.
How severe drought influences ozone pollution
From 2011 to 2015, California experienced its worst drought on record, with a parching combination of high temperatures and low precipitation.
New threat to ozone recovery
A new MIT study, published in Nature Geoscience, identifies another threat to the ozone layer's recovery: chloroform -- a colorless, sweet-smelling compound that is primarily used in the manufacturing of products such as Teflon and various refrigerants.
Ozone hole modest despite optimum conditions for ozone depletion
The ozone hole that forms in the upper atmosphere over Antarctica each September was slightly above average size in 2018, NOAA and NASA scientists reported today.
Increased UV from ozone depletion sterilizes trees
UC Berkeley paleobotanists put dwarf, bonsai pine trees in growth chambers and subjected them to up to 13 times the UV-B radiation Earth experiences today, simulating conditions that likely existed 252 million years ago during the planet's worst mass extinction.
Ozone at lower latitudes is not recovering, despite Antarctic ozone hole healing
The ozone layer -- which protects us from harmful ultraviolet radiation -- is recovering at the poles, but unexpected decreases in part of the atmosphere may be preventing recovery at lower latitudes.
More Ozone News and Ozone Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: The Power Of Spaces
How do spaces shape the human experience? In what ways do our rooms, homes, and buildings give us meaning and purpose? This hour, TED speakers explore the power of the spaces we make and inhabit. Guests include architect Michael Murphy, musician David Byrne, artist Es Devlin, and architect Siamak Hariri.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

What If?
There's plenty of speculation about what Donald Trump might do in the wake of the election. Would he dispute the results if he loses? Would he simply refuse to leave office, or even try to use the military to maintain control? Last summer, Rosa Brooks got together a team of experts and political operatives from both sides of the aisle to ask a slightly different question. Rather than arguing about whether he'd do those things, they dug into what exactly would happen if he did. Part war game part choose your own adventure, Rosa's Transition Integrity Project doesn't give us any predictions, and it isn't a referendum on Trump. Instead, it's a deeply illuminating stress test on our laws, our institutions, and on the commitment to democracy written into the constitution. This episode was reported by Bethel Habte, with help from Tracie Hunte, and produced by Bethel Habte. Jeremy Bloom provided original music. Support Radiolab by becoming a member today at     You can read The Transition Integrity Project's report here.