Four new man-made compounds that deplete our ozone layer have been discovered – three chlorofluorocarbons (CFC) and one hydrochlorofluorocarbon (HCFC). All four trace back to the 1960s, and two of the compounds continue to accumulate in our atmosphere. Their source is unidentified:
We don’t know where the new gases are being emitted from and this should be investigated. Of the four species identified, CFC-113a seems the most worrying as there is a very small but growing emission source somewhere, maybe from agricultural insecticides. We should find it and take it out of production. (Lead researcher Dr Johannes Laube, University of East Anglia)
The researchers estimate that, prior to 2012, more than 74,000 tons of the four compounds combined entered the atmosphere. This is far less than peak emissions of CFCs in the 1980s (which was over one million tones yearly), but it’s a clear violation of the Montreal Protocol.
The Montreal Protocol, which came into effect in 1989, was designed to phase out the use of CFCs, HCFCs, and other ozone depleting substances. The Montreal Protocol has been widely adopted and implemented – Kofi Annan called it perhaps the single most successful international agreement to date.
Here’s NASA’s projection of what our ozone layer would have looked like if we hadn’t implemented the Montreal Protocol:
Image and description via NASA’s Visible Earth:
The series of images starts with 1974, before CFCs had begun to do significant damage to the ozone layer. Concentrations of ozone in the stratosphere over the United States and Canada are high. By 1994, the model predicts that ozone concentrations over the region have fallen from highs above 500 Dobson Units to about 400. By the simulated year 2009, the ozone layer over much of the United States has thinned to only 300 Dobson Units. By 2020, the model predicts that an ozone “hole”—concentrations below 220 Dobson Units—forms over the Arctic as well as the Antarctic. By 2040, the ozone hole is global. The UV index in mid-latitude cities reaches 15 around noon on a clear summer day (10 is considered extreme today).