Review of CFC-11 Distributed Emissions from the Global Emissions Inventory Activity (GEIA)

CFC-11 (CCl3F, trichlorofluoromethane) is now used primarily within rigid
plastic insulating foams ("closed cell foams"). Some material is released into
the atmosphere when the foam is first blown but most of the losses occur in the
long term due to gradual migration of the insulating gas through the cell
walls, with total loss when the equipment is finally removed from service and
scrapped. There are other minor uses in refrigeration and historical use in
aerosol propellant formulations.

As a consequence of the delay between first use and release, it is necessary to
calculate emissions from time series of data on production and sales into
various end-use categories having different release functions. The calculation
method is described in McCulloch et al. (2001).

The calculated global emissions of CFC-11 were distributed among countries
using the distribution of individual national fractions of the world total
Gross Domestic Product, as described in McCulloch et al. (1994). Within each
country, emissions were distributed to individual gridsquares using a
population distribution from Harvard University (Jennifer Logan, personal
communication).

Results are presented here as the percentage distribution among gridsquares.
Absolute emission from each gridsquare in 1986 should be calculated by
multiplying global emission for 1986 in Table 1
("http://geicenter.org/reviews/cfc1 1.html") by the gridsquare percentages in
Table 2. For other years, the
distribution in Table 2 should be applied to the global emission for the
appropriate year. While global emissions change relatively rapidly,
distribution is affected only by relative economic activity and population
dynamics, which have slower rates of change with time. It is expected that the
distribution can be applied to the years 1980 to 1990 without significantly
increasing uncertainty but this has not been tested. It can be applied to years
beyond this range only with caution and new distributions for more recent years
are under development.

Based on McCulloch et al. (2001) the time series (1933 to 2000) of CFC-11
emissions and their uncertainties is shown in
"http://geicenter.org/reviews/cfc1 1.html". From the years 1986 to 2000, the
values are slightly different from those reported in the literature. This is
due to an unexplained change in the UNEP database between successive
publications in 1996 and 2002 which altered the quantities not included in the
AFEAS database. The maximum annual difference between the published data and
that recorded here is 5% and the two data sets are not significantly different
at the 95% confidence level.

Future emissions will be governed by the controls required by the Montreal
Protocol and by the quantity of material currently in the "bank" (that is:
material which is in use but has not yet been emitted). A scenario for future
releases of CFC-11 was described in Madronich and Velders (1999). This scenario
has been updated and will be published in Fraser and Montzka (2003).