OZ10C. Stay Current—The Other Face of Ozone

2024-06-17. What Happens in the Troposphere Doesn’t Stay in the Troposphere. By Rebecca Owen, Eos/AGU. Excerpt: In the final decades of the 20th century, stratospheric ozone depletion—often called, not quite accurately, the ozone hole—was a widespread concern. Halocarbons, including chlorofluorocarbons used as coolants in refrigerators and aerosol spray cans, were linked, beginning in the mid-1970s, to a severely thinning ozone layer. However, global efforts to reduce halocarbon use have since led to a slow but steady recovery of the stratospheric ozone layer. About 90% of Earth’s ozone is in the stratosphere, where it protects humans, plants, and animals from the Sun’s most damaging ultraviolet rays. …the 10% of it that is in the troposphere—the atmospheric layer between Earth’s surface and the stratosphere—can be damaging to human health and the environment. Tropospheric ozone is the primary component of smog, for example, and its concentration has been increasing globally over the past hundred years. …as Prather writes in a new paper, “what happens in the troposphere doesn’t stay in the troposphere.” Some of these molecules travel up into the stratosphere when the two atmospheric layers exchange air. The author suggests that this upward migration of ozone may make it difficult to assess the recovery rate of the depleted stratospheric ozone layer accurately and may also affect how researchers interpret the results of a worldwide reduction in halocarbon use. …about 20% of the observed stratospheric ozone recovery may be attributable to increasing levels of tropospheric ozone. …future studies of ozone depletion should be adjusted accordingly. …(AGU Advances, https://doi.org/10.1029/2023AV001154, 2024)…. Full article at https://eos.org/research-spotlights/what-happens-in-the-troposphere-doesnt-stay-in-the-troposphere.

2020-05-19. Tracking Tropospheric Ozone Since 1979. By David Shultz, Eos/AGU. Excerpt: … The planet’s protective ozone layer, which exists mainly in the stratosphere at altitudes between 15 and 35 kilometers, absorbs ultraviolet radiation from the Sun, shielding the surface from hazardous high-energy light. However, ozone is also found beneath the stratosphere in the troposphere, where the molecule behaves more like a greenhouse gas and contributes to global warming. Ozone concentrations in the troposphere result from an interplay between transport from the stratosphere above and ozone production driven by emissions at the surface. In a new study [https://doi.org/10.1029/2019GL086901], Griffiths et al. model the atmospheric chemistry of ozone in the troposphere and stratosphere between 1979 and 2010…. The scientists quantified effects on tropospheric ozone during that time from both increasing emissions of ozone precursors and losses of stratospheric ozone resulting from the prevalent human usage of chlorofluorocarbons (CFCs), atmospheric pollutants famously responsible for depleting the ozone layer. Overall, their results show that ozone production in the troposphere from anthropogenic sources increased during the study period, with the added pollution almost counterbalancing a decrease in stratosphere-to-troposphere transfer of ozone: Only a slight decrease in tropospheric ozone was detectable, with the two competing factors nearly canceling each other out. More recently, however, between 1994 and 2006, as the effects of bans on CFCs began to influence stratospheric ozone levels, the group’s model shows a slight increase in tropospheric ozone. With the ozone layer recovering, a strengthening of the stratosphere-to-troposphere transport of ozone expected under climate change, and ozone precursor emissions continuing to rise in many places, the team says the results highlight the importance of studying ozone transport from the stratosphere to the troposphere—especially in the midlatitudes in spring, when atmospheric conditions favor such a downward flow of ozone. (Geophysical Research Letters, https://doi.org/10.1029/2019GL086901, 2020)…. [https://eos.org/research-spotlights/tracking-tropospheric-ozone-since-1979]  

2017-11-17. Treaty to Phase Out ‘Greenhouse Gasses on Steroids’ to Enter Force.  By Somini Sengupta, The New York Times. Excerpt: UNITED NATIONS — Hydrofluorocarbons. It’s a mouthful of a name for a chemical that keeps the turkey frozen in our refrigerators and also heats up the planet. Now, a landmark international agreement to eliminate HFCs, as the chemicals are better known, is poised to come into effect. On Friday, Sweden became the 20th country to ratify the treaty…. That meets the threshold for the agreement to enter into force… January 1, 2019. It requires every country in the world to phase out the use of HFCs, compounds that are regarded as a sort of greenhouse gas on steroids, able to trap much more heat in the atmosphere than carbon dioxide. The agreement was reached, after seven painstaking years of negotiations, in October 2016 in Kigali, the capital of Rwanda. Known as the Kigali Amendment to the Montreal Protocol, it required 20 countries to ratify it in order to go into effect — just in time for a global meeting on a broader treaty designed to protect the ozone layer, which starts next week in Montreal. …the ratification sends a message to companies that make the compounds and to companies that use coolants in their products that they will have to come up with alternatives. …The United States has not yet ratified the measure, …and if it fails to ratify the agreement, it could potentially hinder the ability of American companies to sell coolants to other countries that have ratified the agreement. …China, a leading manufacturer of household appliances that contain HFCs, hasn’t yet ratified it either, but is expected to, Mr. Zaelke said…. https://www.nytimes.com/2017/11/17/climate/hfcs-montreal-protocol.html

2012-10-18. Scientists find ozone causes forests to use more water, reducing availability in the Southeast. Phys.org. Forest Service and Oak Ridge National Laboratory (ORNL) scientists have found that rising levels of ozone, a greenhouse gas, may amplify the impacts of higher temperatures and reduce streamflow from forests to rivers, streams, and other water bodies. Such effects could potentially reduce water supplies available to support forest ecosystems and people in the southeastern United States. 

Impacts of ozone, a global scale pollutant, on forests are not well understood at a large scale. This modeling study indicates that current and projected increases in ozone in the 21st century will likely enhance the negative effects of warming on watersheds, aggravating drought and altering stream flow. …Published in the November issue of the journal Global Change Biology, the study suggests that ozone has amplified the effects of warmer temperatures in reducing streamflow in forested watersheds in the southeastern United States. Read more at: http://phys.org/news/2012-10-scientists-ozone-forests-availability-southeast.html

2011 October 11.  Groups Sue After E.P.A. Fails to Shift Ozone Rules.  By John M. Broder, The NY Times.  Excerpt:  …WASHINGTON — Five health and environmental groups sued the Obama administration on Tuesday over its rejection of a proposed stricter new standard for ozone pollution, saying the decision was driven by politics and ignored public health concerns.
The groups said that President Obama’s refusal to adopt the new standard was illegal and left in place an inadequate air quality rule from the Bush administration. Near the end of his presidency, George W. Bush overruled  the Environmental Protection Agency’s scientific advisory panel and set the permissible ozone exposure at 75 parts per billion….  [See also: A Closer look: Setting a ‘safer’ ozone level.  By Jill U. Adams, The Los Angeles Times.]        

2009 Feb 13. USA Today special report on air pollution near schools. USA today used an EPA model to track the path of industrial pollution and mapped the locations of almost 128,000 schools to determine the levels of toxic chemicals outside….
Interactive Map: Schools that ranked the worst.

2009 January 16. Sniffing Out Smog. By Kathleen M. Wong, ScienceMatters@Berkeley, Volume 6, Issue 40. Excerpt: If smog were a kitchen creation, the recipe would go something like this: Start with a miasma of organic hydrocarbons from spilled gasoline, incomplete combustion and trees. Add nitrogen oxides from combustion in factory furnaces and vehicle engines. Zap with a dose of sunlight, and wait. The result: a heaping serving of photochemical smog.
…Atmospheric chemist Ron Cohen studies how these pollutants form, tracks where and how far they travel, and how they get removed from the atmosphere. He then uses this knowledge to understand air quality and the interactions of pollutants with climate. A Berkeley professor of chemistry and earth and planetary sciences, his work provides the factual underpinnings for climate and air pollution models that, ultimately, help keep us all breathing more easily.
…Cohen tracks air pollution from its molecular origins through its metamorphosis into ugly yellow smog. To do this, he designs and builds instruments capable of measuring minute amounts of the chemicals that contribute to air pollution. Armed with these super sniffers, he can track exactly how fast smog forms and how much of it is in the environment.
“We try to understand how these molecules get into the atmosphere, what their chemistry is, and what they’re doing to climate,” Cohen says….

May 3, 2004. NASA RELEASE : 04-147 NASA Satellites And Balloons Spot Airborne Pollution “Train” — NASA scientists discovered pollution could catch an airborne “express train,” or wind current, from Asia all the way to the southern Atlantic Ocean. Scientists believe during certain seasons, as much as half of the ozone pollution above the Atlantic Ocean may be speeding down a “train” track of air from the Indian Ocean. As it rolls along, it picks up more smog from air peppered with thunderstorms that bring it up from the Earth’s surface. Bob Chatfield, a scientist at NASA’s Ames Research Center, Moffett Field, Calif. said, “Man-made pollution from Asia can flow southward, get caught up into clouds, and then move steadily and rapidly westward across Africa and the Atlantic, reaching as far as Brazil.” During those periods of exceptionally high ozone in the South Atlantic, especially during late winter, researchers noticed Indian Ocean pollution follows a similar westward route, wafted by winds in the upper air. They found the pollution eventually piles up in the South Atlantic. “We’ve always had some difficulty explaining all that ozone,” Thompson admitted.

Feb 10, 2004. Tango in the Atmosphere: Ozone and Climate Change. NASA Earth Observatory feature article. Ozone’s impact on climate consists primarily of changes in temperature. The more ozone in a given parcel of air, the more heat it retains. Ozone generates heat in the stratosphere, both by absorbing the sun’s ultraviolet radiation and by absorbing upwelling infrared radiation from the lower atmosphere (troposphere). Consequently, decreased ozone in the stratosphere results in lower temperatures.

November 19, 2003. SAVANNA SMOG – Each August in southern Africa, literally thousands of people equipped with lighters or torches go out into the African savanna, a region dotted with villages and teaming with animals, and intentionally set the dry grasslands ablaze.