[Federal Register Volume 61, Number 13 (Friday, January 19, 1996)]
[Rules and Regulations]
[Pages 1284-1286]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 96-587]



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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 82

[FRL-5400-3]
RIN 2060-AF35


Protection of Stratospheric Ozone: Listing of Global Warming 
Potential for Ozone-Depleting Substances

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of final listing.

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SUMMARY: With this action, the Environmental Protection Agency (EPA or 
the Agency) lists the global warming potentials for ozone-depleting 
substances that are included as class I and class II controlled 
substances, or have been added as class I or class II controlled 
substances, under authority of section 602(e) of the Clean Air Act 
Amendments of 1990 (CAA). Class I and class II controlled substances 
are more fully described in a final rule previously published in the 
Federal Register on May 10, 1995 (60 FR 24970). To meet EPA's statutory 
obligation under the CAA, this listing cites the global warming 
potentials contained in the document, Scientific Assessment of Ozone 
Depletion: 1994, published by the United Nations Environment Programme 
(UNEP) in early 1995. As stated in the CAA, the listing of global 
warming potentials for class I and class II controlled substances 
``shall not be construed to be the basis of any additional regulation 
under this Act.''

DATES: This rule is effective on January 19, 1996.

FOR FURTHER INFORMATION CONTACT: The Stratospheric Ozone Hotline at 1-
800-296-1996, or Tom Land, U.S. Environmental Protection Agency, Office 
of Air and Radiation, Office of Atmospheric Programs, Stratospheric 
Protection Division (6205J), 401 M 

[[Page 1285]]
Street, SW, Washington, DC 20460, (202)-233-9185.

SUPPLEMENTARY INFORMATION:

I. Proposal

    As required by section 602(e) of the CAA, EPA published a notice of 
proposed listing on October 6, 1995, and solicited public comment. As 
stated in that proposal, EPA relied on three scientific documents in 
determining gobal warming potential (GWPs). EPA is referencing those 
three scientific documents and the list of GWPs they contain in order 
to meet the Agency's statutory obligations under section 602(e) of the 
CAA to publish GWPs for class I and class II controlled substances. 
These documents are also referenced in part, for their discussions of 
different radiative forcing indices and the indirect effects of ozone-
depleting substances on radiative forcing. These documents demonstrate 
the state of knowledge and the uncertainties involved in calculating 
the GWPs for class I and class II controlled substances.
    The citation for the three scientific documents that report on GWPs 
for class I and class II controlled substances are:

United Nations Environment Programme (UNEP), February 1995, 
Scientific Assessment of Ozone Depletion: 1994, Chapter 13: ``Ozone 
Depleting Potentials, Global Warming Potentials and Future Chlorine/
Bromine Loading;''
Intergovernmental Panel on Climate Change (IPCC), 1995, Climate 
Change 1994: Radiative Forcing of Climate Change and An Evaluation 
of the IPCC IS92 Emission Scenarios, ``Summary for Policymakers: 
Radiative Forcing of Climate Change,'' pages 32-34; and
Daniel, John S., Susan Solomon and Daniel L. Albritton, January 20, 
1995, Journal of Geophysical Research, Vol. 100, No. D1, ``On the 
evaluation of halocarbon radiative forcing and global warming 
potentials.''

    Chapter 13 in the UNEP, Scientific Assessment and pages 32 through 
34 in the IPCC, Summary for Policymakers describe the factors 
considered in calculating various radiative forcing indices, such as 
(1) the direct GWP, (2) the absolute global warming potential (AGWP), 
and (3) the net GWP per unit mass emission. Chapter 13 of the 
Scientific Assessment and the article by John S. Daniel, et al. in the 
Journal of Geophysical Research describe the indirect feedback effects 
of ozone-depleting substances on the temperature of the atmosphere, and 
therefore the potential indirect effects that depletion of 
stratospheric ozone has on the calculation of the GWP.
    The October 6, 1995 proposed listing contained a full discussion of 
the relevant science. That discussion will not be repeated in this 
notice.

II. Comment on Proposal

    EPA received one comment on the proposed listing of GWPs for class 
I and class II controlled substances. The comment suggested that 
cautionary language be included in order to prepare the reader for 
changing scientific estimates of GWPs, citing work by the IPCC on the 
Second Scientific Assessment of Climate Change that will be published 
early in 1996. EPA adopted these suggestions and changed the caption to 
Appendix I accordingly.
    No comments were received on the proposed GWPs.

III. Listing GWPs for class I and class II Controlled Substances

    With today's action, EPA publishes the GWPs that are listed for 
class I and class II controlled substances in the Scientific Assessment 
of Ozone Depletion: 1994 issued by the United Nations Environment 
Programme (UNEP) under the auspices of the Montreal Protocol in 
February of 1995. The GWPs for class I and class II controlled 
substances as published in the Scientific Assessment are in Appendix I 
to Subpart A--Global Warming Potentials.
    As discussed in the October 6, 1995 proposed listing, the 
Scientific Assessment of Ozone Depletion: 1994 does not list a GWP for 
every controlled substance that is listed in Appendices A and B to 
Subpart A as most recently promulgated in the Federal Register on May 
10, 1995. For some ozone-depleting chemicals scientists have not 
developed a full infrared spectrum that is necessary to calculate the 
relative radiative forcing potential of a substance. Each chemical 
absorbs the Earth-emitted infrared radiation in specific energy (or 
wavelength) bands determined by the quantum-mechanical properties of 
the specific molecule.1 Scientists have not measured the spectral 
region in which some of the ozone-depleting substances absorb infrared 
radiation. In addition, more data must be collected on the tropospheric 
distribution and concentration of some of the chemicals, their 
atmospheric lifetimes, and the interactive atmospheric chemistry in 
order to complete a calculation of the global warming potential for the 
remaining ozone-depleting substances. Scientific centers and academic 
institutions throughout the world are undertaking the necessary 
measurements and studies that are needed to complete the calculations 
of GWPs for other ozone-depleting substances, as well as to revise GWPs 
for those substances listed in Appendix I. EPA believes it is not 
possible at this time to publish GWPs for every ozone-depleting 
substance listed in Appendix A and B to Subpart A because the necessary 
scientific information is not available. EPA will continue to evaluate 
GWPs for class I and class II controlled substances not listed in 
today's action, and revisions to the GWPs for substances that are 
listed, and as deemed appropriate, amend the listing through future 
actions.

    \1\  Wuebbles, Donald J., 1995, ``Weighing Functions for Ozone 
Depletion and Greenhouse Gas Effects on Climate,'' Annual Review of 
Energy and Environment, 20:45-70.
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List of Subjects in 40 CFR Part 82

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Chemicals, Chlorofluorocarbons, Exports, 
Hydrochlorofluorocarbons, Imports, Ozone layer, Reporting and 
recordkeeping requirements, Stratospheric ozone layer.
    Dated: December 26, 1995.
Carol Browner,
Administrator.

    For the reasons set out in the preamble, 40 CFR part 82 is amended 
as follows:

PART 82--PROTECTION OF STRATOSPHERIC OZONE

    1. The authority citation for part 82 continues to read as follows:

    Authority: 42 U.S.C. 7414, 7601, 7671-7671q.

Subpart A--Production and Consumption Controls

    2. Appendix I is added to subpart A to read as follows:
    Appendix I to Subpart A--Global Warming Potentials (mass basis), 
referenced to the Absolute GWP for the adopted carbon cycle model 
CO2 decay response and future CO2 atmospheric concentrations 
held constant at current levels. (Only direct effects are considered.) 

[[Page 1286]]


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                                                                               Global warming potential (time   
                                                                                          horizon)              
           Species (chemical)                    Chemical formula         --------------------------------------
                                                                             20 years    100 years    500 years 
----------------------------------------------------------------------------------------------------------------
CFC-11.................................  CFCl3                                    5000         4000         1400
CFC-12.................................  CF2Cl2                                   7900         8500         4200
CFC-13.................................  CClF3                                    8100        11700        13600
CFC-113................................  C2F3Cl3                                  5000         5000         2300
CFC-114................................  C2F4Cl2                                  6900         9300         8300
CFC-115................................  C2F5Cl                                   6200         9300        13000
H-1301.................................  CF3Br                                    6200         5600         2200
Carbon Tet.............................  CCl4                                     2000         1400          500
Methyl Chl.............................  CH3CCl3                                   360          110           35
HCFC-22................................  CF2HCl                                   4300         1700          520
HCFC-141b..............................  C2FH3Cl2                                 1800          630          200
HCFC-142b..............................  C2F2H3Cl                                 4200         2000          630
HCFC-123...............................  C2F3HCl2                                  300           93           29
HCFC-124...............................  C2F4HCl                                  1500          480          150
HCFC-225ca.............................  C3F5HCl2                                  550          170           52
HCFC-225cb.............................  C3F5HCl2                                 1700          530          170
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 United Nations Environment Programme (UNEP), February 1995, Scientific Assessment of Ozone Depletion: 1994,    
  Chapter 13, ``Ozone Depleting Potentials, Global Warming Potentials and Future Chlorine/Bromine Loading,'' and
  do not reflect review of scientific documents published after that date.                                      

[FR Doc. 96-587 Filed 1-18-96; 8:45 am]
BILLING CODE 6560-50-P