OZ8C. Stay Current—Measuring Ozone

El Niño/Southern Oscillation (ENSO) Diagnostic Discussion

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]  

2019-04-25. Into the overworld: modified spy plane to see whether towering storms pose new threat to ozone layer. By Eli Kintisch, Science Magazine. [https://www.sciencemag.org/news/2019/04/overworld-ex-spy-plane-see-whether-towering-storms-pose-new-threat-ozone-layer] Excerpt: …Lockheed pilot Ron Williams taxied a NASA research jet down a runway in Punta Arenas at the southern tip of Chile. The long, gliderlike wings of the aircraft—a modified Lockheed U-2 spy plane known as the ER-2—were heavy with fuel and scientific instruments.  …Williams watched as the sky above his cockpit turned from blue to purple to black, …. Below, Earth’s curvature appeared. Williams had climbed into the overworld, the heart of the frigid, dry lower stratosphere, some 18 kilometers up. It was August 1987 …Reactions triggered by industrial chemicals appeared to be eating a hole in Earth’s ozone layer, which protects life from harmful ultraviolet (UV) radiation. …Ultimately, the measurements that Williams and other pilots collected over Antarctica in 1987 became iconic—and influential… proving that chlorinated compounds used in refrigerators, spray cans, and industrial processes were destroying stratospheric ozone. The findings helped clear the way for the approval for the Montreal Protocol, a global pact that phased out the worst ozone-destroying compounds. Since then, levels of the chemicals in the atmosphere have decreased, enabling the ozone layer over Antarctica to slowly recover. … More than 3 decades later, NASA’s ER-2 is again preparing to soar to the overworld in search of a potential new threat to the ozone layer. …this time, the flights will take place far from the South Pole, over the U.S. Great Plains. There, scientists suspect, towering summer thunderstorms are lofting water and pollutants high into the stratosphere, where they can catalyze ozone destruction. And researchers worry the problem could worsen as the planet warms….  

2018-11-03. More Evidence Points to China as Source of Ozone-Depleting Gas. By Chris Buckley, The New York Times. [https://www.nytimes.com/2018/11/03/climate/china-ozone-cfcs.html] Excerpt: BEIJING — An environmental group says it has new evidence showing that China is behind the resurgence of a banned industrial gas that not only destroys the planet’s protective ozone layer but also contributes to global warming. The gas, trichlorofluoromethane, or CFC-11, is supposed to be phased out worldwide under the Montreal Protocol, the global agreement to protect the ozone layer. In May, however, scientists published research showing that CFC-11 levels in the atmosphere had begun falling more slowly. Their findings suggested significant new emissions of the gas, most likely from East Asia. Evidence then uncovered by The New York Times and the Environmental Investigation Agency pointed to rogue factories in China as a likely major source. Now, the E.I.A. has prepared a report that it says bolsters the finding that Chinese factories are behind the return of CFC-11. …Chinese officials have said they have already acted vigorously to close rogue chemical makers. They have also asserted that the CFC-11 emissions in question are too large to be solely from those operations….  

2016-10-10. World leaders discuss ban of climate-busting refrigerants. By Robynne Boyd, Nature. Excerpt: After being directed for almost 30 years at substances that destroy ozone, the Montreal Protocol will for the first time target a group of greenhouse gases. Beginning today in Kigali, Rwanda, member states of the United Nations are finalizing the terms of what could be the largest commitment to reducing global warming since the Paris Agreement on climate last December. Delegates are likely to take till the meeting’s final day on 14 October to hammer out the knotty details of an amendment to the protocol. Ideally, the amendment will set the terms for a rapid phasedown of hydrofluorocarbons (HFCs), the most common of which is the refrigerant HFC-134a, which has 1,430 times more warming potential than carbon dioxide (CO2) over 100 years. The amendment would stop the manufacture of HFCs and then reduce their use over time…. See also articles in Science, BBC News, New York Times, and The Washington Post.  http://www.nature.com/news/world-leaders-discuss-ban-of-climate-busting-refrigerants-1.20768

2014-08-20. Ozone-Depleting Compound Persists, NASA Research Shows. Excerpt: NASA research shows Earth’s atmosphere contains an unexpectedly large amount of an ozone-depleting compound from an unknown source decades after the compound was banned worldwide. Carbon tetrachloride (CCl4), which was once used in applications such as dry cleaning and as a fire-extinguishing agent, was regulated in 1987 under the Montreal Protocol along with other chlorofluorocarbons that destroy ozone and contribute to the ozone hole over Antarctica. Parties to the Montreal Protocol reported zero new CCl4 emissions between 2007-2012. However, the new research shows worldwide emissions of CCl4 average 39 kilotons per year, approximately 30 percent of peak emissions prior to the international treaty going into effect. “We are not supposed to be seeing this at all,” said Qing Liang, an atmospheric scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study. “It is now apparent there are either unidentified industrial leakages, large emissions from contaminated sites, or unknown CCl4 sources.”…. http://www.nasa.gov/press/2014/august/ozone-depleting-compound-persists-nasa-research-shows/#.VAp93kiprZE. NASA RELEASE 14-224.

2013-12-09. The Montreal Protocol, a Little Treaty That Could.    Excerpt:  Here is a remarkable fact about global warming: It might be twice as bad right now were it not for a treaty negotiated by a conservative American president, for an entirely different purpose, based on motives no one has ever quite understood. That treaty is known, in shorthand, as the Montreal Protocol. Its formal purpose is to save the ozone layer in the upper atmosphere, which protects the planet and its people from debilitating levels of cancer-causing ultraviolet radiation. The negotiations on behalf of the United States, in the 1980s, were carried out by the Reagan administration. …The Montreal Protocol is widely seen as the most successful global environmental treaty. …the treaty may be even more important in limiting global warming than we thought…. http://www.nytimes.com/2013/12/10/science/the-montreal-protocol-a-little-treaty-that-could.html. Justin Gillis, The New York Times.

2013-06-06.   NASA Flights Target How Pollution, Storms and Climate Mix.  For Excerpt: …NASA aircraft will take to the skies over the southern United States this summer to investigate how air pollution and natural emissions, which are pushed high into the atmosphere by large storms, affect atmospheric composition and climate. …More than 250 scientists, engineers, and flight personnel are participating in the Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign. ….Aircraft and sensors will probe the atmosphere from top to bottom at the critical time of year when weather systems are strong enough and regional air pollution and natural emissions are prolific enough to pump gases and particles high into the atmosphere. The result is potentially global consequences for Earth’s atmosphere and climate. “In summertime across the United States, emissions from large seasonal fires, metropolitan areas, and vegetation are moved upward by thunderstorms and the North American Monsoon,” Toon said. “When these chemicals get into the stratosphere they can affect the whole Earth. They also may influence how thunderstorms behave. With SEAC4RS we hope to better understand how all these things interact.” SEAC4RS will provide new insights into the effects of the gases and tiny aerosol particles in the atmosphere. The mission is targeting two major regional sources of summertime emissions: intense smoke from forest fires in the U.S. West and natural emissions of isoprene, a carbon compound, from forests in the Southeast. Forest fire smoke can change the properties of clouds. The particles in the smoke can reflect and absorb incoming solar energy, potentially producing a net cooling at the ground and a warming of the atmosphere. The addition of large amounts of chemicals, such as isoprene, can alter the chemical balance of the atmosphere. Some of these chemicals can damage Earth’s protective ozone layer. For more information on the mission, visit: http://espo.nasa.gov/missions/seac4rs  ….http://www.nasa.gov/home/hqnews/2013/jun/HQ_13-167_SEAC4RS_Campaign.html. NASA Release 13-167.

2013-01-08.  Solar Variability and Terrestrial Climate | NASA Science News.  Excerpt: …In the galactic scheme of things, the Sun is a remarkably constant star.  While some stars exhibit dramatic pulsations, wildly yo-yoing in size and brightness, and sometimes even exploding, the luminosity of our own sun varies a measly 0.1% over the course of the 11-year solar cycle.  There is, however, a dawning realization among researchers that even these apparently tiny variations can have a significant effect on terrestrial climate. A new report issued by the National Research Council (NRC), “The Effects of Solar Variability on Earth’s Climate” [at http://www.nap.edu/catalog.php?record_id=13519] lays out some of the surprisingly complex ways that solar activity can make itself felt on our planet. …Greg Kopp of the Laboratory for Atmospheric and Space Physics at the University of Colorado, pointed out that … “Even typical short term variations of 0.1% in incident irradiance exceed all other energy sources (such as natural radioactivity in Earth’s core) combined,” he says. Of particular importance is the sun’s extreme ultraviolet (EUV) radiation, which …varies not by a minuscule 0.1%, but by whopping factors of 10 or more.  This can strongly affect the chemistry and thermal structure of the upper atmosphere.  …In recent years, researchers have considered the possibility that the sun plays a role in global warming. After all, the sun is the main source of heat for our planet. The NRC report suggests, however, that the influence of solar variability is more regional than global…. Read the full article: http://science.nasa.gov/science-news/science-at-nasa/2013/08jan_sunclimate/

2012 February 23.  NOAA, NASA activate new satellite instrument to monitor health and recovery of Earth’s ozone layer. Excerpt: …The Ozone Mapper Profiler Suite, or OMPS, is one of five new instruments flying aboard NASA’s Suomi National Polar-orbiting Partnership satellite (Suomi NPP), which was launched on October 28, 2011. OMPS measures stratospheric ozone, which has eroded over the years as a result of chlorine and bromine from human-produced substances such as chlorofluorocarbons (CFCs) and halons….
…OMPS is designed to look at the upper parts of the atmosphere and tell where ozone is distributed. It will help verify the beginning of the recovery of the ozone layer during the coming few decades, a crucial period when the layer is expected to recover from the effects of the ozone depleting substances….

2011 October 20.  NASA RELEASE 11-357: NASA, NOAA Data Show Significant Antarctic Ozone Hole Remains.  Excerpt: The Antarctic ozone hole, which yawns wide every Southern Hemisphere spring, reached its annual peak on Sept. 12. It stretched to 10.05 million square miles, the ninth largest ozone hole on record. Above the South Pole, the ozone hole reached its deepest point of the season on Oct. 9, tying this year for the 10th lowest in this 26-year record….
…”The colder than average temperatures in the stratosphere this year caused a larger than average ozone hole,” said Paul Newman, chief scientist for atmospheres at NASA’s Goddard Space Flight Center in Greenbelt, Md. “Even though it was relatively large, the area of this year’s ozone hole was within the range we’d expect given the levels of manmade ozone-depleting chemicals that continue to persist in the atmosphere.”…

2011 October 2. SpaceMath@NASA Problem 446: Arctic Ozone Hole Continues to Grow in 2011. Students estimate the area of the Arctic ozone hole, and work with the concept of parts-per-million to estimate total ozone volume lost. See also Press Release: NASA Leads Study of Unprecedented Arctic Ozone Loss: http://www.nasa.gov/topics/earth/features/arctic20111002.html

SpaceMath@NASA Problem 447: The Arctic’s Vanishing Ozone Layer. Students use ozone data for the Arctic region between 1979 and 2011 to graph the tabulated data, perform simple regression analysis, and forecast trends into the future. How much will there be in the year 2030?  See also: Press Release: NASA Leads Study of Unprecedented Arctic Ozone Loss http://www.nasa.gov/topics/earth/features/arctic20111002.html

2011 October 2. NASA RELEASE 11-329: NASA Leads Study Of Unprecedented Arctic Ozone Loss.  Excerpt: WASHINGTON — A NASA-led study has documented an unprecedented depletion of Earth’s protective ozone layer above the Arctic last winter and spring caused by an unusually prolonged period of extremely low temperatures in the stratosphere.
The study, published online Sunday in the journal Nature, finds the amount of ozone destroyed in the Arctic in 2011 was comparable to that seen in some years in the Antarctic, where an ozone “hole” has formed each spring since the mid 1980s. The stratospheric ozone layer, extending from about 10 to 20 miles (15 to 35 kilometers) above the surface, protects life on Earth from the sun’s harmful ultraviolet rays.
…The scientists found that at some altitudes, the cold period in the Arctic lasted more than 30 days longer in 2011 than in any previously studied Arctic winter, leading to the unprecedented ozone loss. Further studies are needed to determine what factors caused the cold period to last so long. …

2009 September 21. Ozone layer depletion leveling off. ESA News. Excerpt: By merging more than a decade of atmospheric data from European satellites, scientists have compiled a homogeneous long-term ozone record that allows them to monitor total ozone trends on a global scale – and the findings look promising. 
Scientists merged monthly total ozone data derived from the vertically downward-looking measurements of the GOME instrument on ESA’s ERS-2 satellite, SCIAMACHY on ESA’s Envisat and GOME-2 on the European Meteorological Satellite Organization’s MetOp-A.
“We found a global slightly positive trend of ozone increase of almost 1% per decade in the total ozone from the last 14 years: a result that was confirmed by comparisons with ground-based measurements,” said Diego G. Loyola R. who worked on the project with colleagues from the German Aerospace Center (DLR).
…Having access to these atmospheric satellite data over long periods is important for scientists to identify and analyse long-term trends and changes. In addition to monitoring ozone trends, scientists will continue to monitor ozone-depleting substances that were phased out under the Montreal Protocol but continue to linger in the atmosphere….

2007 September 13. NASA KEEPS EYE ON OZONE LAYER AMID MONTREAL PROTOCOL’S SUCCESS. Excerpt: “The Montreal Protocol has been a resounding success,” said Richard Stolarski, a speaker at the symposium from NASA’s Goddard Space Flight Center, Greenbelt, Md. “The effect can be seen in the leveling off of chlorine compounds in the atmosphere and the beginning of their decline.”
… “The goal now is to ensure that CFCs and other emissions continue to fall to below the levels that produce an ozone hole,” said Goddard’s Anne Douglass, the deputy project scientist for Aura. “This won’t happen until about 2070.”
NASA and National Oceanic and Atmospheric Administration scientists announced in 2006 that the hole was the largest ever observed, at 10.6 million square miles. The size of the hole will approach its annual peak in late September. Scientists at the symposium will discuss 20 years of scientific progress, as well as how best to monitor the atmosphere to ensure the goals of the treaty are realized.

2007 June 27. NASA RELEASE: 07-144. NASA AIRBORNE EXPEDITION CHASES CLIMATE, OZONE QUESTIONS. WASHINGTON — NASA’s Tropical Composition, Cloud and Climate Coupling (TC4) field campaign will begin this summer in San Jose, Costa Rica, with an investigation into how chemical compounds in the air are transported vertically into the stratosphere and how that transport affects cloud formation and climate.
The study will begin the week of July 16 with coordinated observations from [7] satellites, [3] high-flying NASA research aircraft, balloons and ground-based radar. The targets of these measurements are the gases, aerosols and ice crystals that flow from the top of the strong storm systems that form over the warm tropical ocean. These storm systems pump air more than 40,000 feet above Earth’s surface, where it can influence the composition of the stratosphere, home of our planet’s protective ozone layer. …The effort runs through Aug. 8. It is NASA’s largest Earth science field campaign of the year. “A mission this complex, with three aircraft, deployment sites in Costa Rica and Panama, and more than 400 people involved, can be a real challenge,” said Mission Project Manager Marilyn Vasques of NASA Ames Research Center, Moffett Field, Calif….
Along the coasts of Colombia and Panama south of Costa Rica, the warm summer waters of the Pacific Ocean are a fertile breeding ground for the type of heat-driven, or convective, storm systems the mission is targeting. …Mission scientists want to know what effect a warming climate with rising ocean temperatures will have on the intensity of these storm systems. …These tropical convective systems also may play a role in the recovery of the ozone layer. …Mission scientists will investigate whether the rapid movement of air in these strong convective systems provides an express route for ozone-destroying compounds to reach the stratosphere. …For more information about NASA’s TC4 mission, visit: http://www.espo.nasa.gov/tc4

2007 January 29. Analyzing the Antarctic Ozone Hole. NASA. The Antarctic ozone hole is bigger than ever. This troubling news was reported in October by scientists from NASA and the National Oceanic and Atmospheric Administration. “Analyzing the Antarctic Ozone Hole,” a chapter of the Web-based Earth Exploration Toolbook, provides guidance and the tools necessary for middle and high school students to perform their own studies of the ozone hole using data collected by a NASA satellite instrument, the Total Ozone Mapping Spectrometer. …Using image analysis software available online, students quantify each year’s ozone hole by measuring the number of pixels covered by colors representing ozone levels below a certain threshold value. Students then import their measurements into a spreadsheet program where they graph annual changes in the size of the ozone hole. Students are encouraged to consider what might account for the year-to-year changes, to outline a plan for finding out what could have caused one year to be different than others, and to develop a strategy for conducting a similar study of the Northern Hemisphere’s Arctic region….

2006 December 14. NASA TROPICAL OZONE STUDIES YIELD SURPRISES. NASA Earth Observatory News. – Two new NASA-funded studies of ozone in the tropics using NASA satellite data are giving scientists a fuller understanding of the processes driving ozone chemistry and its impacts on pollution and climate change.

2006 October 19. NASA AND NOAA ANNOUNCE ANTARCTIC OZONE HOLE IS A RECORD BREAKER (RELEASE: 06-338). NASA and National Oceanic and Atmospheric Administration (NOAA) scientists report this year’s ozone hole in the polar region of the Southern Hemisphere has broken records for area and depth. …”From September 21 to 30, the average area of the ozone hole was the largest ever observed, at 10.6 million square miles,” said Paul Newman, atmospheric scientist at NASA’s Goddard Space Flight Center, Greenbelt, Md. If the stratospheric weather conditions had been normal, the ozone hole would be expected to reach a size of about 8.9 to 9.3 million square miles, about the surface area of North America. The Ozone Monitoring Instrument on NASA’s Aura satellite measures the total amount of ozone from the ground to the upper atmosphere over the entire Antarctic continent. …Scientists from NOAA’s Earth System Research Laboratory in Boulder, Colo., use balloon-borne instruments to measure ozone directly over the South Pole. …nearly all of the ozone in the layer between eight and 13 miles above the Earth’s surface had been destroyed. In this critical layer, the instrument measured a record low of only 1.2 DU., having rapidly plunged from an average non-hole reading of 125 DU in July and August. “These numbers mean the ozone is virtually gone in this layer of the atmosphere,” said David Hofmann, director of the Global Monitoring Division at the NOAA Earth System Research Laboratory. …”We now have the largest ozone hole on record,” said Craig Long of NCEP. As the sun rises higher in the sky during October and November, this unusually large and persistent area may allow much more ultraviolet light than usual to reach Earth’s surface in the southern latitudes.

2006 January 23. NASA to Fly into Tropical “Portal” to the Stratosphere. NASA scientists are leading an airborne field experiment to a warm tropical locale to take a close look at a largely unexplored region of the chilly upper atmosphere.

Feb 2005 Civil Aircraft for the Regular Investigation of the atmosphere Based on and Instrument Container http://www.caribic-atmospheric.com/ (CARIBIC) is an innovative scientific project to study important chemical and physical processes in the upper troposphere and lowermost stratosphere. The underlying philosophy is to use passenger aircraft for making measurements during long distance flights. Accordingly, an airfreight container with scientific apparatus is placed in the forward cargo-bay of the aircraft. 

Sept, 2004. Think Molecularly, Act Globally. by David Pescovitz. When NASA’s ER-2 stratospheric aircraft returns from another trip to 70,000 feet above the earth, it may be carrying a special payload back for UC Berkeley professor Kristie Boering. The small canister inside the modified spy plane provides Boering, an assistant professor of chemistry and earth and planetary science, with clues into the human impact on global climate and how the ozone layer may recover over the next century. Amazingly, the canister appears to be empty. That’s because Boering’s understanding of atmospheric chemistry comes from studying the air up there. ScienceMatters@Berkeley 

July 15, 2004, NASA RELEASE : 04-217  Aura Launched, To Better Understand The Air We Breathe — Aura, a mission dedicated to the health of the Earth’s atmosphere, successfully launched today… NASA’s latest Earth-observing satellite, Aura will help us understand and protect the air we breathe. …Aura will help answer three key scientific questions: Is the Earth’s protective ozone layer recovering? What are the processes controlling air 

April 23, 2004. NASA RELEASE : 04-138 . Arctic Ozone Loss More Sensitive To Climate Change Than Thought. A cooperative study involving NASA scientists quantifies, for the first time, the relationship between Arctic ozone loss and changes in the temperature of Earth’s stratosphere. The results indicate the loss of Arctic ozone due to the presence of industrial chlorine and bromine in Earth’s atmosphere may well be sensitive to subtle changes in stratospheric climate. Such ozone depletion leads to increased exposure to harmful, ultraviolet solar radiation at Earth’s surface. According to the study, the sensitivity of Arctic ozone to temperature is three times greater than predicted by atmospheric chemistry models. This leads to the possibility decreases in stratospheric temperatures may have significantly larger impacts on future Arctic ozone concentrations than have been expected in the past. Dr. Markus Rex of the Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany, led the study. It also included scientists from NASA’s Jet Propulsion Laboratory (JPL), Pasadena, Calif. The researchers analyzed more than 2,000 balloon measurements collected over the past 12 years.

Total Ozone Mapping Spectrometer (TOMS) http://toms.gsfc.nasa.gov/

July 29, 2003. RELEASE: 03-253; NASA OBSERVATIONS CONFIRM EXPECTED OZONE LAYER RECOVERY. NASA satellite observations have provided the first evidence the rate of ozone depletion in the Earth’s upper atmosphere is decreasing. This may indicate the first stage of ozone layer recovery. 

January 25, 2003 Solar Radiation and Climate Experiment (SORCE) SCHEDULED FOR LAUNCH. The Solar Radiation and Climate Experiment (SORCE) is a NASA-sponsored satellite mission, scheduled for launch January 25, 2003, that will provide state-of-the-art measurements of incoming x-ray, ultraviolet, visible, near-infared, and total solar radiation. The measurements provided by SORCE specifically address long-term climate change, natural variability and enhanced climate prediction, and atmospheric ozone and UV-B radiation. These measurements are critical to studies of the Sun; its effect on our Earth system; and its influence on humankind. For more information, see: http://lasp.colorado.edu/sorce/

September 30, 2002 – UNUSUALLY SMALL ANTARCTIC OZONE HOLE THIS YEAR ATTRIBUTED TO EXCEPTIONALLY STRONG STRATOSPHERIC WEATHER SYSTEMS — Scientists from NASA and the Commerce Department’s National Oceanic and Atmospheric Administration (NOAA) have confirmed the ozone hole over the Antarctic this September is not only much smaller than it was in 2000 and 2001, but has split into two separate “holes.” Goddard Space Flight Center Top Story.

October 16, 2001 — 2001 OZONE HOLE ABOUT THE SAME SIZE AS PAST THREE YEARS Satellite data show the area of this year’s Antarctic ozone hole peaked at about 26 million square kilometers — roughly the size of North America — making the hole similar in size to those of the past three years. … RELEASE: 01-198 

THE INCREDIBLE SHRINKING OZONE HOLE After reaching a record-breaking size in mid-September, 2001 the ozone hole over Antarctica has made a surprisingly hasty retreat, disappearing completely by November 19, NASA scientists said. The ozone hole waxes and wanes with the seasons every year, slowly vanishing as the Southern Hemisphere reaches the peak of its summer. But this year the hole closed up earlier than in recent years; for the last three years the hole has lingered on well into December, according to Dr. Richard McPeters, principal investigator for NASA’s Total Ozone Mapping Spectrometer (TOMS) at the NASA Goddard Space Flight Center. 

1998-Executive Summary of the most recent WMO/UNEP assessment (Scientific Assessment of Ozone Depletion: 1998) 

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