Each year, ozone-depleting compounds in the upper atmosphere destroy the protective ozone layer, and in particular above Antarctica. The ozone layer acts as Earth's sunscreen by absorbing harmful ultraviolet radiation from incoming sunlight that can cause skin cancer and damage plants, among other harmful effects to life on Earth. While these different compounds each release either reactive chlorine or bromine, the two active ozone-destroying ingredients, during a series of chemical reactions, the molecules have a range of different lifetimes in the atmosphere that can affect their ultimate impact on the ozone layer and its future recovery.
n a Perspective piece appearing in the Dec. 8 issue of Science, NASA researchers discuss the nuances that distinguish three categories of compounds and their impacts on upper atmospheric ozone: long-lasting and human-made compounds, short-lived and human-made compounds, and compounds that are short-lived and naturally emitted from the ocean. All of the long-lasting and some of the anthropogenic short-lived compounds are controlled by the Montreal Protocol in order to reduce their impact on ozone. The researchers find that long-lasting compounds still dominate the outlook for ozone recovery.
This discussion is part of an on-going scientific debate about the impact of short-lived ozone-depleting compounds that stay in the atmosphere for less than six months, whose human-produced emissions have risen. It is relevant to the work being done by the United Nations Environment Programme that administers the Montreal Protocol and its amendments, the seminal global agreement to ban and phase out ozone-destroying compounds. Currently only ozone-depleting substances with atmospheric lifetimes ranging from a year to over 100 years, are controlled because they linger in the atmosphere long enough to reach the upper atmosphere, called the stratosphere. Shorter-lived compounds are unregulated as their impacts are less significant.
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Image Source: NASA
