September 16, 2014

Good news on ozone layer should spur climate action

by Bonnie Denmark

For the first time since 1980, the ozone layer that shields us from harmful radiation is repairing itself after being eaten away over decades by human-produced chemicals. The good news comes just in time to celebrate the twentieth annual International Day for the Preservation of the Ozone Layer on September 16. The United Nations Environmental Programme (UNEP) and the World Meteorological Organization (WMO) announced that the ozone layer is on target for recovery by the middle of this century, thanks to an international cooperative effort to phase out chemicals recognized as ozone-depleting substances.

The success was set in motion by the pioneering work of chemists Mario Molina and F. Sherwood “Sherry” Rowland.  In a 1974 article in Nature, Molina and Rowland proposed that chlorofluorocarbons (CFCs), the popular chemical compounds known as freon that were used worldwide in aerosol cans and a host of other common products, were destroying Earth’s protective ozone layer.

The ozone layer absorbs damaging ultraviolet radiation, protecting us on Earth’s surface. When CFCs are released into the atmosphere, these chemicals drift upward over a span of several decades until they eventually reach the stratosphere. Here the CFCs, which are relatively inert in the lower atmosphere, are broken apart by radiation with a calamitous outcome. The result is a thinning concentration of ozone in the protective layer across the globe and a hole in the ozone layer over the South Pole.

Purple and dark blue areas indicate the hole in the ozone layer. Note change from 1979 (left) to 2008 (right). (NASA)

Molina and Rowland’s research eventually led to the Montreal Protocol on Substances That Deplete the Ozone Layer, an international treaty which called for a phase-out of chemicals that destroy the ozone layer. Their work also earned the scientists the 1995 Nobel Prize in Chemistry.

The damage to the ozone layer took years to create and is taking years to remedy. “If you have a problem of this magnitude, simply turning off the source of emission doesn’t immediately begin to solve the problem,” UNEP Executive Director Achim Steiner said in a September 10 press conference at the United Nations in New York. Therefore, the success of the Montreal Protocol is assessed at intervals. In the latest assessment more than 25 years after the Protocol was first enacted, 300 scientists, including Mario Molina, have determined that the ozone layer is finally making progress toward recovery. The treaty has succeeded in reducing ozone-depleting substances by 98 percent, averting millions of cases of skin cancer and tens of millions of cases of cataracts along with damage to crops and marine life (UNEP 2014 Highlights).

In an Associated Press interview, Molina called the latest ozone news “a victory of diplomacy and for science and for the fact that we were able to work together” and said he didn’t expect to live to see the day when the ozone would make a comeback. His Nobel Prize co-recipient, Rowland, died in 2012.

Lest we get too excited, the announcement comes with a caution. Molina says of the UNEP/WMO Assessment findings, “The precedent is truly important because society is facing another serious global environmental problem, namely climate change,” an issue to which Molina has dedicated himself for many years.

Human activities have impacted and will continue to impact the composition of Earth’s atmosphere. Ironically, the hydrofluorocarbons (HFCs) that were introduced to replace CFCs come with their own problems since they are a major source of greenhouse gas. Even though they do not damage the ozone layer, HFCs will have a negative impact on the global climate, particularly since their emissions are currently growing at  about 7 per cent every year, according to the Assessment. For an explanation of greenhouse gases and their effect on the atmosphere, see our module The Carbon Cycle: What Goes Around Comes Around.

Climate issues are at the forefront of UNEP/WMO focus. WMO Secretary-General Michel Jarraud says, “International action on the ozone layer is a major environmental success story. This should encourage us to display the same level of urgency and unity to tackle the even greater challenge of climate change. This latest assessment provides solid science to policy-makers about the intricate relationship between ozone and climate and the need for mutually-supportive measures to protect life on Earth for future generations” (UNEP 2014 Highlights).

Appropriately, the slogan for this year’s International Day for the Preservation of the Ozone Layer is “The Mission Goes On.”



You can listen here to the audio from the September 10, 2014, press conference announcing major findings of the Assessment for Decision-Makers: Scientific Assessment of Ozone Depletion 2014, held at the United Nations in New York.

For ways to celebrate Ozone Day, visit the United Nations Environmental Programme’s 2014 International Day for the Preservation of the Ozone Layer webpage.


Written by

Bonnie Denmark holds an MA in linguistics and teacher certification in English, ESL, and Spanish. She has devoted her professional life to educational and accessibility issues as a computational linguist, multimedia curriculum developer, educator, and writer. She has also worked nationally and internationally as a language instructor, educational technology consultant, and teacher trainer. Bonnie joined the Visionlearning team as a literacy specialist in 2011, assisting the project by developing comprehension aids for science modules and creating other STEM learning materials.