Topic 3a - Part 2: Stratospheric ozone and CFCs – Detailed insights from satellite data and models
Chlorofluorocarbons (CFCs) are organic molecules that contain carbon, chlorine, and fluorine atoms. After their invention in 1928, CFCs were widely used in manufacturing processes due to their non-toxic, non-flammable nature and were released into the atmosphere from various sources such as air-conditioning, refrigeration, blowing agents in foams, insulations and packing materials, propellants in aerosol cans, and solvents.
Studies undertaken by various scientists during the 1970s revealed that CFCs released into the atmosphere accumulate in the stratosphere, where they had a damaging effect on the ozone layer. In 1976, the U.S. National Academy of Sciences (NAS) released a report that confirmed the scientific credibility of the ozone depletion hypothesis. NAS continued to publish assessments of related science for the next decade.
In 1985, British Antarctic Survey scientists presented the first satellite image of the ozone hole over Antarctica. A few years later atmospheric chemist Susan Soloman proposed that the hole was created by chemical reactions on polar stratospheric clouds (PSCs) which cause a localised and seasonal increase in the amount of chlorine present in active, ozone-destroying forms. There are now many satellite instruments which monitor ozone, including the Ozone Monitoring Instrument (OMI) on the Aura satellite and the Global Ozone Monitoring Experiment-2 (GOME-2) instrument on the Metop series of satellites.
In this video Dr Johannes Flemming explores detailed images of the vertical structure of ozone concentrations over Antarctica.
Prof. John Burrows
Dr Annette Ladstaetter Weissenmayer
Dr Johannes Flemming
Optional mini task
NASA has a website called NASA Ozone Watch which is dedicated to providing images, data and information on atmospheric ozone. This is free to access and available for everyone to use.
Visit NASA Ozone Watch and have a look at the ozone movies. A full table of all ozone movies is available in the multimedia section. Select two videos from different years, do you notice any differences in the ozone hole? Discuss your findings below whilst stating the dates you looked at.
Don’t forget you can download the video, transcript and take any quizzes available with the links on the right.
These 3 images are cross sections of the Antarctic ozone hole on different dates, 1st August, 14th September and the 25th of September respectively. The red area is ozone concentrations, where the redder the colour the more ozone.
2017 total column ozone anomalies from GOME-2 measurements with respect to the 1998-2008 mean determined from the merged multi-sensor data combining GOME, SCIAMACHY, and GOME-2
Time-series of annual mean total ozone in four zonal bands (a-d) and polar (60°-90°) total ozone in March (NH) and October (SH) . In March (NH) and October (SH) are the months when polar ozone losses usually are largest. The dotted grey lines in each panel show the average ozone level from 1970 to 1979 calculated from the WOUDC data.
Size of the ozone hole over Antarctica from 1/7 to 31/12 for the years 2002-2017 (2017 in red, 2015 in blue and 2002 in green). The size is defined as the area south of 62-90S with ozone total columns below 220 DU. The data are taken from the CAMS interim reanalysis (2003-2016), the CAMS NRT (Near Real Time) forecast (2017) and ERA5 (2002)