Refrigerants for the 21st Century
18. Have we Done Enough?

One provision of the Montreal Protocol calls for periodic scientific assessment of O3 depletion.  The 1998 assessment demonstrates just how effective our efforts to protect the stratospheric O3 are becoming. 

This assessment reveals how complicated whole-earth conditions remain and how many kinds of data must be accumulated to determine the complete picture:

• The link between long-term buildup of chlorine and the decline of O3 in the upper atmosphere has been firmly established.

• The springtime Antarctic O3 hole continues unabated.

• The total combined abundance of O3-depleting compounds in the lower atmosphere peaked in about 1994 and is now slowly declining.   Total chlorine is also declining.

• The observed abundances of the HCFC and HFC as substitutes for CFCs are increasing.  In 1996, the HCFCs contributed about 5% of the tropospheric chlorine load.  Nevertheless, the HCFCs contribute only 10% of the total tropospheric chlorine growth rate since the 1980s.

• Current total ozone in the northern hemisphere The rate of decline of stratospheric O3 at mid latitudes has slowed.  The projections of O3 loss made in a 1994 assessment were larger than actually occurred.  The observed total atmospheric column O3 losses in the mid-latitudes are:

  Season	%-Loss 1979to1994-7
  Northern Mid-Latitudes - Winter/Spring	5.4
  Northern Mid-Latitudes - Summer/Fall	2.8
  Southern Mid-Latitudes - Year Round	5.0

• The late-winter/spring O3 values in the Arctic were unusually low in six of the last nine years.  The stratospheric weather in these six years was unusually cold for protracted periods of time.

• Stratospheric O3 losses have caused a cooling of the global lower stratosphere and global average-negative radiative forcing of the climate system.

• Observations and models further confirm that stratospheric sulfate aerosol and polar stratospheric clouds play a key role in O3 loss chemistry through heterogeneous reactions that activate halogen species and deactivate nitrogen species.

Ash Cloud over the Phillipines from Mt. Pinatubo - 1991(NOAA)

Two recent volcanic eruptions - El Chicon (1982) and Mount Pinatubo (1991) - both temporarily increased stratospheric sulfate aerosols by more than ten-fold.  This results from millions of tons of sulfur dioxide in the volcanic gases.

• Increased penetration of UV radiation to the troposphere as a result of stratospheric O3 depletion influences key photochemical processes in the troposphere.  A 1% decrease in global total O3 leads to an increase of 0.7-1.0% in globally averaged tropospheric OH radical which affects the lifetime of several climate-related gases.

• Large reductions in the production and atmospheric release of O3 depleting substances(ODSs) have been achieved by the Montreal Protocol and its Amendments and Adjustments.  Without such controls and assuming an annual 3% growth rate, the ODSs would have led to an equivalent effective chlorine loading of 17 parts per billion by the year 2050.  The changes anticipated from the Montreal Protocol should reduce this load to about 2 parts per billion by 2050.   At this level, atmospheric chlorine will be at about the 1980 level.  You can see production and sales data as collected by AFEAS.

• The stratospheric O3   layer will slowly recover over the next 50 years.  Any reduction in compliance to the Montreal Protocol will delay this anticipated recovery.

• The issues of O3 depletion and climate change such as global warming are interconnected.  We can anticipate that HFCs will contribute to the mechanisms for decreased planetary radiation that may cause warming. Thus the Montreal and the Kyoto protocols that deal with global warming are also interconnected.  For example, decisions made under the Kyoto Protocol regarding control of HFCs may affect the ability to phase out O3   depleting substances.

Under the best compliance scenario, it will take until the middle of the 21st century for stratospheric O3  to recover.  Unfortunately, problems have already arisen with this scenario.  CFCs from non complying foreign producers are being smuggled into the United States.  The level of this illegal activity has been second only to the smuggling of drugs. In additon to being cheaper than the HFC alternatives, these contraband CFCs avoid the high taxes imposed by the U.S. Government on the remaining legal CFCs still in use.  Russia, because of its economic difficulties, has fallen behind its schedule for ending CFC production. 

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