The Long and the Short of It - The Changing Arctic Environment: The Arctic Messenger - page 340

The Montreal Protocol includes a mechanism that requires parties to regularly review mon-
itoring information on the concentrations of substances that deplete the ozone layer, in-
cluding CFCs. These studies showed that as a result of actions taken by countries to com-
ply with the protocol, the atmospheric concentrations of these long-lived chemicals are
no longer increasing. However, substances that were introduced into the market to replace
CFCs and that were thought to be relatively benign have now also appeared in the strato-
sphere. Fortunately, this tendency has been “caught” through the monitoring review pro-
cess and the “new” ozone-depleting substances are now also controlled under the protocol.
Future needs:
It is with good justification that the Montreal Protocol is widely considered to be the
most successful international environmental agreement. It is expected that a return to
pre-1980 ozone levels at Northern Hemisphere mid-latitudes could occur by (or before)
2050 and even rise above 1980 levels by the latter part of the present century. The Arc-
tic will recover a little more slowly. Although it does seem that everything that should
be done is being done, there are two major caveats. The widespread reduction in emis-
sions of earlier ozone-depleting substances was achieved by replacing them with oth-
er substances, particularly HFCs. HFCs are benign to stratospheric ozone but are very
powerfulGHGs.Second,theworkofJohannesLaubeandcolleagues,publishedin2014,
shows that we should never assume we have identified all the ozone-depleting sub-
stances present in the atmosphere.