Ozone in the atmosphere found to have weakened one of Earth's main cooling mechanisms
Date: March 31, 2022
Source: University of Reading
Summary: New research reveals ozone in the lower atmosphere in particular contributed to warming in the Southern Ocean - which absorbs much of the planet's excess heat - more than previously realized. The study shows that ozone is more than just a pollutant, but also may be playing a significant role in climate change.
Ozone may be weakening one of the Earth's most important cooling mechanisms, making it a more significant greenhouse gas than previously thought, research has found.
A new study has revealed that changes to ozone levels in the upper and lower atmosphere were responsible for almost a third of the warming seen in ocean waters bordering Antarctica in the second half of the 20th century.
The deep and rapid warming in the Southern Ocean affects its role as one of the main regions for soaking up excess heat as the planet warms.
The majority of this warming was the result of ozone increases in the lower atmosphere. Ozone -- one of the main components of smog -- is already hazardous as a pollutant, but the research shows it may also play a significant role in driving climate change in the coming years.
Dr Michaela Hegglin, an Associate Professor in atmospheric chemistry and one of the study's authors, said: "Ozone close to Earth's surface is harmful to people and the environment, but this study reveals it also has a big impact on the ocean's ability to absorb excess heat from the atmosphere.
"These findings are an eye-opener and hammer home the importance of regulating air pollution to prevent increased ozone levels and global temperatures rising further still."
The new research by an international team of scientists, and led by the University of California Riverside, is published in Nature Climate Change.
The team used models to simulate changes in ozone levels in the upper and lower atmosphere between 1955 and 2000, to isolate them from other influences and increase the currently poor understanding of their impact on the Southern Ocean heat uptake.
These simulations showed that a decrease in ozone in the upper atmosphere and increase in the lower atmosphere both contributed to warming seen in the upper 2km of the ocean waters in the high latitudes by overall greenhouse gas increases.
They revealed that the increased ozone in the lower atmosphere caused 60% of the overall ozone-induced warming seen in the Southern Ocean over the period studied -- far more than previously thought. This was surprising because tropospheric ozone increases are mainly thought of as a climate forcing in the Northern hemisphere since that is where the main pollution occurs.
Ozone hit the headlines in the 1980s when a hole was discovered in the ozone layer high in the atmosphere over the South Pole, due to damage caused by chlorofluorocarbons (CFCs), a gas used in industry and consumer products.
The ozone layer is vital as it filters dangerous ultraviolet radiation from reaching Earth's surface. This discovery led to the Montreal Protocol, an international agreement to halt the production of CFCs.
Dr Hegglin said: "We have known for a while that ozone depletion high in the atmosphere has affected surface climate in the Southern Hemisphere. Our research has shown that ozone increases in the lower atmosphere due to air pollution, which occurs primarily in the Northern Hemisphere and 'leaks' into the Southern Hemisphere, is a serious problem as well.
"There is hope to find solutions, and the success of the Montreal Protocol at cutting CFC use shows that international action is possible to prevent damage to the planet."
Ozone is created in the upper atmosphere by interaction between oxygen molecules and UV radiation from the sun. In the lower atmosphere, it forms due to chemical reactions between pollutants like vehicle exhaust fumes and other emissions.
Changes in ozone concentrations in the atmosphere affect westerly winds in the Southern Hemisphere as well as causing contrasting levels of salt and temperature close to the surface in the Southern Ocean. Both affect ocean currents in distinct ways, thereby affecting ocean heat uptake.
Journal Reference:
Wei Liu, Michaela I. Hegglin, Ramiro Checa-Garcia, Shouwei Li, Nathan P. Gillett, Kewei Lyu, Xuebin Zhang, Neil C. Swart. Stratospheric ozone depletion and tropospheric ozone increases drive Southern Ocean interior warming. Nature Climate Change, 2022; DOI: 10.1038/s41558-022-01320-w
Ozone may be weakening one of the Earth's most important cooling mechanisms, making it a more significant greenhouse gas than previously thought, research has found.
A new study has revealed that changes to ozone levels in the upper and lower atmosphere were responsible for almost a third of the warming seen in ocean waters bordering Antarctica in the second half of the 20th century.
The deep and rapid warming in the Southern Ocean affects its role as one of the main regions for soaking up excess heat as the planet warms.
The majority of this warming was the result of ozone increases in the lower atmosphere. Ozone -- one of the main components of smog -- is already hazardous as a pollutant, but the research shows it may also play a significant role in driving climate change in the coming years.
Dr Michaela Hegglin, an Associate Professor in atmospheric chemistry and one of the study's authors, said: "Ozone close to Earth's surface is harmful to people and the environment, but this study reveals it also has a big impact on the ocean's ability to absorb excess heat from the atmosphere.
"These findings are an eye-opener and hammer home the importance of regulating air pollution to prevent increased ozone levels and global temperatures rising further still."
The new research by an international team of scientists, and led by the University of California Riverside, is published in Nature Climate Change.
The team used models to simulate changes in ozone levels in the upper and lower atmosphere between 1955 and 2000, to isolate them from other influences and increase the currently poor understanding of their impact on the Southern Ocean heat uptake.
These simulations showed that a decrease in ozone in the upper atmosphere and increase in the lower atmosphere both contributed to warming seen in the upper 2km of the ocean waters in the high latitudes by overall greenhouse gas increases.
They revealed that the increased ozone in the lower atmosphere caused 60% of the overall ozone-induced warming seen in the Southern Ocean over the period studied -- far more than previously thought. This was surprising because tropospheric ozone increases are mainly thought of as a climate forcing in the Northern hemisphere since that is where the main pollution occurs.
Ozone hit the headlines in the 1980s when a hole was discovered in the ozone layer high in the atmosphere over the South Pole, due to damage caused by chlorofluorocarbons (CFCs), a gas used in industry and consumer products.
The ozone layer is vital as it filters dangerous ultraviolet radiation from reaching Earth's surface. This discovery led to the Montreal Protocol, an international agreement to halt the production of CFCs.
Dr Hegglin said: "We have known for a while that ozone depletion high in the atmosphere has affected surface climate in the Southern Hemisphere. Our research has shown that ozone increases in the lower atmosphere due to air pollution, which occurs primarily in the Northern Hemisphere and 'leaks' into the Southern Hemisphere, is a serious problem as well.
"There is hope to find solutions, and the success of the Montreal Protocol at cutting CFC use shows that international action is possible to prevent damage to the planet."
Ozone is created in the upper atmosphere by interaction between oxygen molecules and UV radiation from the sun. In the lower atmosphere, it forms due to chemical reactions between pollutants like vehicle exhaust fumes and other emissions.
Changes in ozone concentrations in the atmosphere affect westerly winds in the Southern Hemisphere as well as causing contrasting levels of salt and temperature close to the surface in the Southern Ocean. Both affect ocean currents in distinct ways, thereby affecting ocean heat uptake.
Journal Reference:
Wei Liu, Michaela I. Hegglin, Ramiro Checa-Garcia, Shouwei Li, Nathan P. Gillett, Kewei Lyu, Xuebin Zhang, Neil C. Swart. Stratospheric ozone depletion and tropospheric ozone increases drive Southern Ocean interior warming. Nature Climate Change, 2022; DOI: 10.1038/s41558-022-01320-w
Smoke from Australia’s intense fires in 2019 and 2020 damaged the ozone layer
Increasingly large blazes threaten to undo decades of work to help Earth’s protective layer
A towering cloud of smoke rises over the Green Wattle Creek bushfire on December 21, 2019, near the township of Yanderra in New South Wales, Australia.
By Carolyn Gramling
MARCH 17, 2022
Towers of smoke that rose high into the stratosphere during Australia’s “black summer” fires in 2019 and 2020 destroyed some of Earth’s protective ozone layer, researchers report in the March 18 Science.
Chemist Peter Bernath of Old Dominion University in Norfolk, Va., and his colleagues analyzed data collected in the lower stratosphere during 2020 by a satellite instrument called the Atmospheric Chemistry Experiment. It measures how different particles in the atmosphere absorb light at different wavelengths. Such absorption patterns are like fingerprints, identifying what molecules are present in the particles.
The team’s analyses revealed that the particles of smoke, shot into the stratosphere by fire-fueled thunderstorms called pyrocumulonimbus clouds, contained a variety of mischief-making organic molecules (SN: 12/15/20). The molecules, the team reports, kicked off a series of chemical reactions that altered the balances of gases in Earth’s stratosphere to a degree never before observed in 15 years of satellite measurements. That shuffle included boosting levels of chlorine-containing molecules that ultimately ate away at the ozone.
Ozone concentrations in the stratosphere initially increased from January to March 2020, due to similar chemical reactions — sometimes with the contribution of wildfire smoke — that produce ozone pollution at ground level (SN: 12/8/21). But from April to December 2020, the ozone levels not only fell, but sank below the average ozone concentration from 2005 to 2019.
Earth’s ozone layer shields the planet from much of the sun’s ultraviolet radiation. Once depleted by human emissions of chlorofluorocarbons and other ozone-damaging substances, the layer has been showing signs of recovery thanks to the Montreal Protocol, an international agreement to reduce the atmospheric concentrations of those substances (SN: 2/10/21).
But the increasing frequency of large wildfires due to climate change — and their ozone-destroying potential — could become a setback for that rare climate success story, the researchers say (SN: 3/4/20).
CITATIONS
P. Bernath, C. Boone and J. Crouse. Wildfire smoke destroys stratospheric ozone. Science. Vol. 375, March 18, 2022, p. 1,292. doi: 10.1126/science.abm5611
.
Increasingly large blazes threaten to undo decades of work to help Earth’s protective layer
A towering cloud of smoke rises over the Green Wattle Creek bushfire on December 21, 2019, near the township of Yanderra in New South Wales, Australia.
By Carolyn Gramling
MARCH 17, 2022
Towers of smoke that rose high into the stratosphere during Australia’s “black summer” fires in 2019 and 2020 destroyed some of Earth’s protective ozone layer, researchers report in the March 18 Science.
Chemist Peter Bernath of Old Dominion University in Norfolk, Va., and his colleagues analyzed data collected in the lower stratosphere during 2020 by a satellite instrument called the Atmospheric Chemistry Experiment. It measures how different particles in the atmosphere absorb light at different wavelengths. Such absorption patterns are like fingerprints, identifying what molecules are present in the particles.
The team’s analyses revealed that the particles of smoke, shot into the stratosphere by fire-fueled thunderstorms called pyrocumulonimbus clouds, contained a variety of mischief-making organic molecules (SN: 12/15/20). The molecules, the team reports, kicked off a series of chemical reactions that altered the balances of gases in Earth’s stratosphere to a degree never before observed in 15 years of satellite measurements. That shuffle included boosting levels of chlorine-containing molecules that ultimately ate away at the ozone.
Ozone concentrations in the stratosphere initially increased from January to March 2020, due to similar chemical reactions — sometimes with the contribution of wildfire smoke — that produce ozone pollution at ground level (SN: 12/8/21). But from April to December 2020, the ozone levels not only fell, but sank below the average ozone concentration from 2005 to 2019.
Earth’s ozone layer shields the planet from much of the sun’s ultraviolet radiation. Once depleted by human emissions of chlorofluorocarbons and other ozone-damaging substances, the layer has been showing signs of recovery thanks to the Montreal Protocol, an international agreement to reduce the atmospheric concentrations of those substances (SN: 2/10/21).
But the increasing frequency of large wildfires due to climate change — and their ozone-destroying potential — could become a setback for that rare climate success story, the researchers say (SN: 3/4/20).
CITATIONS
P. Bernath, C. Boone and J. Crouse. Wildfire smoke destroys stratospheric ozone. Science. Vol. 375, March 18, 2022, p. 1,292. doi: 10.1126/science.abm5611
.
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