6.Near-term Climate Protection and Clean Air Benefits: Actions for Controlling Short-Lived Climate...

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HFCs: A Crical Link in ProtecngClimate and the Ozone Layer

A UNEP Synthesis Report

[ADVANCE COPY]


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Published by the United Nations Environment Programme (UNEP), November 2011

Copyright UNEP 2011

ISBN: 978-92-807-3228-3

DEW/1469/NA

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UNEP 2011. HFCs: A Critical Link in Protecting Climate and the Ozone Layer. United Nations Environment Programme

(UNEP), 36pp

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HFCs:A Crical Link in Protecng

Climate and the Ozone Layer

A UNEP Snhess Repr

Nveber 2011


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5/40ACkNowlEdgEmENtS HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyER 3

The United Naons Environment Programme (UNEP) would like to thank the Steering Commiee, all the lead authors,

reviewers and the Secretariat for their contribuon to the development of this report.

The following individuals and/or organizaons have provided scienc input to the report. Authors have contributed

to this report in their individual capacit and their organizaons are menoned for idencaon purposes.

Steering Commiee Members:

Joseph Alcamo Chair (UNEP), Marco Gonzalez (UNEP),

Slvie Lemmet (UNEP), Kaveh Zahedi (UNEP), Rajendra

Shende (TERRE Polic Centre, India).

Lead Authors:

A.R. Ravishankara - Coordinator (Naonal Oceanic and

Atmospheric Administraon NOAA, USA), Guus J.M.

Velders (Naonal Instute for Public Health and the

Environment RIVM, The Netherlands), M.K. Miller

(Touchdown Consulng, Belgium), Mario Molina (Centro

Mario Molina, Mexico and Universit of California, San

Diego, USA).

Scienc and Technical Reviewers:

Roberto R. Aguilo (Universidad Nacional de Lujn,

Argenna), Stephen O. Andersen (Instute for Governance

& Sustainable Development IGSD, USA), Atul Bagai (UNEP),

Guangming Chen (China Instute for Refrigeraon, China),

Didier Coulomb (Internaonal Instute of Refrigeraon,France), John Daniel (Naonal Oceanic and Atmospheric

Administraon NOAA, USA), David A. Fahe (Naonal

Oceanic and Atmospheric Administraon NOAA, USA),

Neil Harris (Universit of Cambridge, United Kingdom),

Sanjeev Jain (Indian Instute of Technolog, India), Sitaram

Joshi (Naonal Bureau of Standards and Metrolog,

Nepal), Janusz Kozakiewicz (Industrial Chemistr Research

Instute, Poland), Janos Mat (Greenpeace Internaonal),

Mack McFarland (Dupont, USA), John N. Muthama

(Universit of Nairobi, Kena), Stefan Reimann (Swiss

Federal Laboratories for Materials Science and Technolog

Empa, Switzerland), Agusn Sanchez (SEMARNAT,

Mexico) William Sturges (Universit of East Anglia, United

Kingdom), Donald Wuebbles (Universit of Illinois, USA),

Sed M. Zubair (King Fahd Universit, Saudi Arabia).

Contributors of Informaon/Data:

John Daniel (Naonal Oceanic and Atmospheric

Administraon NOAA, USA), Stephen Montzka (Naonal

Oceanic and Atmospheric Administraon NOAA, USA),

Stefan Reimann (Swiss Federal Laboratories for Materials

Science and Technolog Empa, Switzerland), Paul

Newman (NASA Goddard Space Flight Centre, USA), David

A. Fahe (Naonal Oceanic and Atmospheric Administraon

NOAA, USA).

Editorial Support:

Joseph Alcamo (UNEP), Alison Colls - Science Editor (Icicle

Climate Communicaons, Switzerland), Sunda A. Leonard

(UNEP).

UNEP Secretariat:Sunda A. Leonard - Project Management, Harsha Dave,

Linda Duquesno, Ron Wi.

Producon Team:

Hilar Barnes (Robsondowr Ltd), Pouran Ghaapour

(UNON), Gideon Mureithi (UNON), Paul Odhiambo (UNON),

Neea Patel (UNEP), Audre Ringler (UNEP).

Layout and Prinng:

UNON, Publishing Services Secon,

ISO 14001:2004 - cered.

Acknowledgements


6/404 HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyER

Contents

Acknowledgements 3

Glossary 5

Foreword 8

Execuve summary 9

1. Montreal Protocol and ozone layer protecon 13

1.1 The Montreal Protocol has successfull protected the ozone laer 13

1.2 The Montreal Protocol is graduall phasing out ODSs 14

1.3 The Montreal Protocol is working as expected and intended 16

1.4 HFCs are substutes for ODSs 16

1.5 Man HFCs are potent greenhouse gases 17

2. Climate benets of the Montreal Protocol 18

2.1 Acons under the Montreal Protocol have reduced and avoided emissions of important greenhouse gases 18

2.2 Acons under the Montreal Protocol have reduced radiave forcing b ODSs 18

2.3 Some of the climate benets of the Montreal Protocol have been oset 18

2.4 The climate benets of the Montreal Protocol are greater than the Koto target 19

3. HFCs and climate change 20

3.1 The atmospheric abundances of HFCs are increasing rapidl 20

3.2 Equivalent CO2 emissions of HFCs are sll small compared to other emissions but increasing rapidl 20

3.3 The current contribuon of HFCs to climate forcing is small but rapidl growing 20

3.4 Dierent tpes of future HFC emissions scenarios have been constructed 22

3.5 HFC emissions have the potenal to become ver large and at least partl oset the climate benets

of the Montreal Protocol 22

3.6 The radiave forcing of HFCs is also projected to signicantl increase 23

3.7 HFC emissions also have indirect climate eects 243.8 Dierent HFCs have dierent atmospheric lifemes and var in their abilit to inuence climate 24

3.9 A scenario in which onl low-GWP HFCs are used has a low climate inuence 26

4. Alternaves to high-GWP HFCs 27

4.1 Methods for reducing the inuence of high-GWP HFCs on climate have been idened 27

4.2 Low-GWP alternaves oer the potenal to minimize the inuence of high-GWP HFCs on climate 27

4.3 Low-GWP alternaves are alread in commercial use 29

4.4 More alternaves are under development 29

4.5 Case stud: Alternaves adopted b manufacturers of household refrigeraon and small air-condioning units 30

4.6 Case stud: Technical developments in vehicle air-condioning sstems 30

4.7 Case stud: End-user companies pledge to use low-GWP technologies 31

4.8 There are barriers to the adopon of low-GWP alternaves but also man was to overcome them 314.9 There is no one-size ts all alternave to high-GWP HFCs 33

4.10 Going forward 33

References 34


7/40gloSSARy HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyER 5

Glossary

Arcle 5 Countries: An part of the Montreal Protocol

who is a developing countr and whose annual per capitaconsumpon of the controlled substances is below the

limits set in Arcle 5 of the Protocol.

Atmospheric lifeme: Time it takes for 67% of a molecules

to be removed from the atmosphere in the absence of

emissions.

Atmospheric mixing rao: The fraconal composion of a

chemical in the atmosphere relave to the sum of all air

molecules in the atmosphere.

The mixing rao of a chemical is the number of molecules

of X in a unit volume divided b the number of air molecules

in a unit volume. Mixing raos are usuall expressed as

parts-per-million (ppm), parts-per-billion (ppb), or parts-

per-trillion (ppt).

Carbon dioxide equivalent (CO2eq):A simple wa to place

emissions of various climate change agents on a common

foong to account for their eect on climate.

A quant that describes, for a given mixture and amount of

greenhouse gas, the amount of carbon dioxide that would

have the same global warming abilit, when measured over

a specied mescale.

Chlorouorocarbons (CFCs): Molecules containing carbon,uorine, and chlorine. CFCs are the major ozone depleng

substances alread phased out b the Montreal Protocol.

Man CFCs are potent greenhouse gases.

Drop-in alternaves: Substances that can be used in

exisng equipment with ver lile or no modicaon

to the equipment. Drop-in replacements were used to

quickl replace CFCs. Examples include use of HCFC-22 in

air condioners. Such replacements are also possible with

some HFCs.

Global Warming Potenal (GWP): A relave index that

enables comparison of the climate eect of the emissionsof various greenhouse gases (and other climate changing

agents). Carbon dioxide, the greenhouse gas that causes

the greatest radiave forcing because of its overwhelming

abundance, is chosen as the reference gas.

GWP is also dened as an index based on the radiave

forcing of a pulsed injecon of a unit mass of a given well-

mixed greenhouse gas in the present-da atmosphere,

integrated over a chosen me horizon, relave to the

radiave forcing of carbon dioxide over the same me

horizon. The GWPs represent the combined eect of the

diering atmospheric lifemes (i.e., how long these gases

remain in the atmosphere) and their relave eecveness

in absorbing outgoing thermal infrared radiaon. The

Koto Protocol is based on GWPs from pulse emissions

over a 100-ear me frame.

20-year GWP: Global warming potenal (see above)

calculated for a me horizon of 20 ears.

100-year GWP: Global warming potenal (see above)

calculated for a me horizon of 100 ears.

GWP Weighng: A mathemacal product of the emissions

in tonnes and the GWP of a substance. GWP weighng is

used rounel to evaluate the relave climate impact of

emissions of various gases (b mass).

Hydrochlorouorocarbons (HCFCs):Chemicals that contains

hdrogen, uorine, chlorine, and carbon. The do deplete

the ozone laer, but have less potenc compared to CFCs.

Man HCFCs are potent greenhouse gases.

Hydrofuorocarbons (HFCs): Chemicals that contains hydrogen,

uorine, and carbon. They do not deplete the ozone layer and

have been used as substutes for CFCs and HCFCs. Many HFCs

are potent greenhouse gases.

Indirect climate eects: A metric that accounts for climate

eects caused b the use of a product, such as increased

energ consumpon.

Addional climate forcing due to the energ used, or

saved, during the applicaon or product lifeme, as wellas the energ used to manufacture the product, and

an ODSs or HFCs used. For example, insulang foam


8/406 HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyER gloSSARy

products in buildings and appliances reduces energconsumpon, whereas refrigeraon and air-condioning

sstems consume energ over their lifemes. Analses

of the total potenal climate impact of specic products

can be esmated b life ccle climate performance (LCCP)

or similar models that account for all direct and indirect

contribuons.

Indirect radiave forcing: A metric that accounts for

eects on the climate sstem of a given agent as a result

of changes induced in other climate forcing agents. For

example, the climate eects of ozone laer depleon

caused b ODSs.

In this report, indirect radiave forcing refers to the

change in ozone radiave forcing due to the addion of

ODSs. Stratospheric ozone losses are generall thought to

cause a negave radiave forcing, cancelling part of the

increased radiave forcing arising from the direct inuence

of the halocarbons. The magnitude of the indirect eect is

strongl dependent on the altude prole of the halogen-

induced ozone loss and will var depending on the source

gas considered.

Intervenon scenarios: A scenario where acon is taken to

change the amount of emissions of a given chemical.

Non-arcle 5 countries: Developed countries.

Not-in-kind alternaves: Products or technologies not

using halocarbons. Not-in-kind alternave technologies

achieve the same product objecve without the use of

halocarbons, tpicall b using an alternave approach or

unconvenonal technique. Examples include the use of

sck or spra pump deodorants to replace CFC-12 aerosol

deodorants; the use of mineral wool to replace CFC, HFC or

HCFC insulang foam; and the use of dr powder inhalers

(DPIs) to replace CFC or HFC metered dose inhalers (MDIs).

Ozone depleng substances: Chemicals that can depletethe ozone laer. In this report, the are restricted to those

listed b the Montreal Protocol in their annexes.

Ozone Depleon Potenal (ODP): A measure of theextent of ozone laer depleon b a given ozone depleng

substance, relave to that depleted b CFC-11. (CFC-11 has

an ODP of 1.0).

There are man variants of ODPs. In this report, we use

onl the stead-state ODP, which is used b the Montreal

Protocol. Stead-state ODP is dened b the me-

integrated change of global ozone due to a unit mass

emission of the ODS at the Earths surface, relave to that

from a similar emission of a unit mass of CFC-11.

Radiave Forcing: A measure of how a climate forcing

agent inuences the energ balance of Earth, with a posivevalue indicang a net heat gain to the lower atmosphere,

which leads to a globall average surface temperature

increase, and a negave value indicang a net heat loss.

Radiave forcing is the instantaneous change in the net,

downward minus upward, irradiance (expressed in W m-2)

at the tropopause due to a change in an external driver of

climate change, such as, a change in the concentraon of a

greenhouse gas (e.g., carbon dioxide), land use change, or

the output of the Sun. Radiave forcing is computed with

all tropospheric properes held xed at their unperturbed

values, and aer allowing for stratospheric temperatures, if

perturbed, to readjust to radiave-dnamical equilibrium.

Short-lived climate forcers: Substances (mainl chemicals)

that inuence climate but whose inuence is quickl

reduced once their emissions cease. These molecules are

quickl removed from the atmosphere.

Stratospheric ozone: Ozone (O3) present in the stratosphere

located between roughl 15 and 45 km above Earths

surface.

Transional substute: Substutes for CFCs, Halons,

and few other ODSs that were introduced with the idea

that their use would cease aer more environmentallacceptable alternaves were found.


9/40ACRoNymS HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyER 7

AC Air-condioning

ASHRAE American Societ of Heang, Refrigerang, and Air Condioning EngineersCDM Clean Development Mechanism

CFC Chlorouorocarbon

Co2 Carbon dioxide

FTOC Foam Technical Opons Commiee of TEAP

GHG Greenhouse gas

GTZ Deutsche Gesellscha fuer Technische Zusammenarbeit

GWP Global Warming Potenal (for specic me horizons)

HCFC Hdrochlorouorocarbon

HFC Hdrouorocarbon

IPCC Intergovernmental Panel on Climate Change

LCCP Life-Ccle Climate Performance

MAC Mobile Air CondioningMCII Mullateral Fund Climate Impact Indicator

MDI Metered dose inhaler

MLF Mullateral Fund for the implementaon of the Montreal Protocol

ODP Ozone Depleon Potenal

ODS Ozone depleng substance

RTOC Refrigeraon Technical Opons Commiee of TEAP

SAE Societ of Automove Engineers Internaonal

SAP Scienc Assessment Panel

TEAP Technolog and Economic Assessment Panel

TFA Triuoroacec acid

UNEP United Naons Environment Programme

UNFCCC UN Framework Convenon on Climate ChangeUS EPA United States Environmental Protecon Agenc

WMO World Meteorological Organizaon

Acronyms


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Foreword

A.R. Ravishankara

Naonal Oceanic

and Atmospheric

Administraon, USA

The Montreal Protocol on Substances that Deplete the Ozone Laer has emerged

as one of the trul outstanding success stories of internaonal cooperaon onsustainable development.

Since the 1980s, naons have worked together to phase-out the chemicals that

have been damaging and degrading the ozone laer the Earths protecve shield

that lters out harmful levels of ultra-violet light.

More recentl science has spotlighted that this internaonal eort has also spared

humanit a signicant level of climate changeperhaps buing back to date man-

ears-worth of greenhouse gas emissions or avoided annual emissions, between 1988

and 2010 equal to about 8 Gt of CO2 equivalent.

This is because the original ozone-depleng substances, which the Montreal Protocol

is phasing out, such as chlorouorocarbons (CFCs) and hdrochlorouorocarbons

(HCFCs), are not onl ozone-depleng but also serious climate-damaging gases.

The focus of this report is the opportunit for acon on the latest replacementchemicals known as hdrourocarbons (HFCs).

HFCs are excellent substutes for use in products such as refrigerators and industrial

air condioners, but the are extremel powerful global warming gases.

ths repr, HFCs: A Crical Link in Protecng Climate and the Ozone Layer,sas ha

the current contribuon to climate forcing b HFCs is less than one per cent. However,

it warns that HFCs are rapidl increasing in the atmosphere as the are adopted as

ozone-friendl alternaves. Emissions of HFCs are growing at a rate of 8% per ear,

and b 2050, without acon, the could rise so high that the almost cancel the

tremendous climate benets won earlier b the phase-out of CFCs and other ozone-

depleng substances.

This ma challenge internaonal eorts to keep a global temperature rise under

2 degrees C or less this centurthe target agreed at the UN climate convenonmeeng in 2009 and rearmed in Cancun in 2010.

The good news, outlined in this report, is that alternaves exist that can assist in

bringing down the projected growth in HFCs, if urgent acon is taken.

There are diverse range of alternavesfrom designing buildings that avoid the

need for air condioning to use of alternave substances such as hdrocarbons and

ammonia, to use of HFCs with less global warming potenal and shorter lifemes than

those of current concern.

The current gap between the ambion of naons and the scienc realit of where

the world is heading with respect to climate change requires that all opons are

considered and all transformave acons pursued.

Acon on the main greenhouse gases such as CO2 and methane is at the core of that

challenge. But acon on other pollutants can also assist.This scienc report underlines that HFCs need to be a clearer part of that landscape

and brought more decisivel into the suite of opons for acon that can assist in

meeng and keeping the 2 degree C target.

Achim Steiner

UN Under-Secretar-General,

UNEP Execuve Director

Mario Molina

Centro Mario Molina,

Mexico and Universit ofCalifornia, San Diego, USA

8 HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyERFoREwoRd


11/40EXECUTIVE SUMMARy HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyER 9

HCFCs

CFCs

HFCs

1200

1000

800

600

400

200

0

Consumpon(ktonnesper

year)

Consumpton

1950 1960 1970 1980 1990 2000 2010

Year

Execuve Summary

The Montreal Protocol has successfully protected the

stratospheric ozone layerThe Protocol has been an eecve instrument for protecng

the Earths stratospheric ozone laer b providing an

internaonal framework for phasing out ozone depleng

substances (ODSs), including chlorouorocarbons (CFCs) and

hdrochlorouorocarbons (HCFCs). The phase-out of ODSs

has been accomplished b curtailing their producon and

consumpon.

The phase-out of ODSs requires either substute chemicals

or other approaches, and hdrouorocarbons (HFCs) have

become the major replacements in man ODS applicaons

(Figure ES 1). HFCs, which have no known natural sources,

are used because the do not deplete the stratosphericozone laer and can be used with relave ease (technicall)

in place of CFCs and HCFCs.

The Montreal Protocol has also eecvely protected

climate

Since most ODSs are also potent greenhouse gases, acons

under the Montreal Protocol have had the ver posive

side eect of substanall reducing a main source of global

warming. Indeed, the phasing out of ODSs led to a drop

between 1988 and 2010 of about 8.0 GtCO2eq per ear

(gigatonnes equivalent CO2 emissions) (Figure ES 2). The

avoided annual emission of ODSs (approximatel 10 Gt

Co2eq in 2010 alone) is about ve mes greater than the

annual emissions reducon target for the rst commitment

period (20082012) of the Koto Protocol (UNEP 2011); it is

one of the largest reducons to date in global greenhouse

gas emissions.

The climate benets of the Montreal Protocol may be

oset by increases in HFCs

Like the ODSs the replace, man HFCs are potent

greenhouse gases. Although their current contribuon toclimate forcing is less than 1% of all other greenhouse gases

combined, HFCs have the potenal to substanall inuence

climate in the future.

HFCs are rapidl increasing in the atmosphere as a

result of their use as ODS replacements. For example, CO 2equivalent emissions of HFCs (excluding HFC-23) increased

b approximatel 8% per ear from 2004 to 2008.

Figure ES 1. Global consumpon (in kilotonnes per ear) of ozone depleng CFCs and HCFCs. The

phasing in of HFCs as replacements for CFCs is evident from the decrease in CFC usage concomitantwith the increasing usage of HFCs. Use of HCFCs also increased with the decreasing use of CFCs.

HCFCs are being replaced in part b HFCs as the 2007 Adjustment to the Montreal Protocol on HCFCs

connues to be implemented. Thus, HFCs are increasing primaril because the are replacing CFCs

and HCFCs.


12/4010 HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyEREXECUTIVE SUMMARy

CO2eq emissions

1950 1970 1990

Observatons Scenarios

2010 2030 2050

Year

0

2

4

6

8

10

12

CO

2eqemissions(GtCO

2eqperyear)

14

HCFCs

CFCsHFCs

Low-GWP HFCs

As a consequence, the abundances of HFCs in the

atmosphere are also rapidl increasing (Figure ES 3). For

example, HFC-134a, the most abundant HFC, has increased

b about 10% per ear from 2006 to 2010.

In the future, HFC emissions have the potenal to become

ver large. Under current pracces, the consumpon of

HFCs is projected to exceed b 2050 the peak consumpon

level of CFCs in the 1980s. This is primaril due to growing

demand in emerging economies and increasing populaons.

Without intervenon, the increase in HFC emissions is

projected to oset much of the climate benet achieved b

the earlier reducon in ODS emissions. Annual emissions

of HFCs are projected to rise to about 3.5 to 8.8 Gt CO2eq

in 2050 which is comparable to the drop menoned above

in ODS annual emissions of 8.0 GtCO2eq between 1988 and

2010.

To appreciate the signicance of projected HFC

emissions, the would be equivalent to 7 to 19% of the CO2

emissions in 2050 based on the IPCCs Special Report on

Emissions Scenarios (SRES), and equivalent to 18 to 45% of

Co2 emissions based on the IPCCs 450 ppm CO2 essns

pathwa scenario. There is, of course, inherent uncertaint

in such projecons.

If HFC emissions connue to increase, the are likel

to have a noceable inuence on the climate sstem. B

2050, the buildup of HFCs is projected to increase radiave

forcing b up to 0.4 W m-2 relave to 2000 (Figure ES 4).

This increase ma be as much as one-h to one-quarter

of the expected increase in radiave forcing due to the

buildup of CO2 since 2000, according to the SRES emission

scenarios.

However, the future radiave forcing b HFCs in 2050

would be relavel small, at the same level as it is toda

(


13/40EXECUTIVE SUMMARy HFCs, Cl imAtE PRotECtioN ANd tHE ozoNE lAyER 11

Figure ES 3. Global average atmospheric abundances of four major HFCs used as ODS replacements

(HFC-134a, HFC-143a, HFC-125 and HFC-152a) since 1990. This illustrates the rapid growth in

atmospheric abundances as a result of rapid increases in their emissions. These increases are

aributed to their increased usage in place of CFCs and/or HCFCs. The increase in HFC-23, the second

most abundant HFC in the atmosphere, are not shown since it is assumed that the majorit of this

chemical is produced as a bproduct of HCFC-22 and not because of its use as a replacement for CFCs

and HCFCs. The abundance of HFC-23 was 22 ppt in 2008, with an annual growth rate of 0.83 ppt

(roughl 4% per ear) in that ear.

Figure ES 4. Projected radiave forcing of climate b HFCs and CO2 since 2000, when the inuence of

HFCs was essenall zero. The HFC climate forcing for an upper range scenario is compared with the

Co2 forcing for the range of scenarios from IPCC-SRES and the 450 ppm CO 2 stabilizaon scenario.

Clearl, the contribuon of HFCs to radiave forcing could be ver signicant in the future; b 2050,

it could be as much as a quarter of that due to CO2 increases since 2000, if the upper range HFC

scenario is compared to the median of the SRES scenario. Alternavel, the contribuon of HFCs

to radiave forcing could be one-h of the radiave forcing due to CO2 increases since 2000, if the

upper range HFC scenario is compared to the upper range of the SRES scenario. The contribuon of

HFCs to radiave forcing could also be as much as 40% of the radiave forcing b CO2 under the 450

ppm stabilizaon scenario.

1990 1995 2000 2005 2010

Year

0

10

20

30

40

50

60

Abundances(ppt)

HFC abundances

HFC -134a

HFC -143a

HFC -152a

HFC -125

2.0

1.5

1.0

0.5

0.0

Changeinradiatveforcing(Wm

-2)

Change in radiatve

forcing since 2000

2000 2010 2020 2030 2040 2050

Year

SRES CO2 range

Stabilizaon ofCO2 at 450 ppm

Upper range

HFC scenario


14/4012 HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyEREXECUTIVE SUMMARy

onl make up a small fracon of other sectors at present,although the have the potenal to substanall increase

their market share.

While there is some concern that replacing HFCs ma

lead to lower energ ecienc, recent studies have shown

that a nunber of sstems using low-GWP substances have

equal or beer energ ecienc than sstems using high-

GWP HFCs.

It is not unusual that barriers stand in the wa of changes

in technolog, and this is also the case for alternaves to

high-GWP HFCs. These barriers include: the need for further

technical developments, risks due to ammabilit and

toxicit, regulaons and standards that inhibit the use ofalternaves, insucient suppl of components, investment

costs, and lack of relevant skills among technicians.

But the current use of alternaves to high-GWP HFCs

demonstrates that these barriers can be overcome b

acvies such as, research and technological improvements,

revised technical standards, training and technical

assistance, as well as infrastructure developments.

While various alternave opons are being evaluated or

further developed, there are also some known measures

that can be implemented to reduce emissions of HFCs.

For example, the design of equipment can be modied to

reduce leakage and the quant of HFC used, and technicalprocedures can be modied to reduce emissions during

manufacture, use, servicing and disposal of equipment.

As a general conclusion about HFC alternaves, it canbe said that there is no one-size-ts-all soluon. The

soluon that works best will depend on man factors such

as the local situaon for producon and use, the costs of

dierent alternaves, the availabilit of components, and

the feasibilit of implementaon.

Going Forward

To sum up, although replacing ozone depleng substances

with HFCs helps to protect the ozone laer, increasing use

and consequentl emissions of high-GWP HFCs are likel to

undermine the ver signicant climate benets achieved

b ODS phase-out.

It is sll possible to maintain these climate benets

because ozone-friendl and climate-friendl alternaves

exist for high-GWP HFCs in a number of sectors. But further

work needs to be done before full advantage of these

alternaves can be taken. It is important, for example, to

update esmates of the climate inuence of HFC scenarios;

to further analze technical and regulator barriers, and

how to overcome them; and to examine the life-ccle

impacts of various opons to ensure that the do not have

unacceptable side eects on societ or the environment.

B pursuing this and other work, sustainable opons for

protecng both the ozone laer and the global climate arelikel to be found.


15/40

Chapter 1:

Montreal Protocol and ozonelayer protecon

The Montreal Protocol is an example of how countries

can cooperate to successfull combat a serious global

environmental problem. The acons agreed upon under the

Protocol have led to a mel phase-out of ozone depleng

substances and there is alread evidence that the presence

of these substances is decreasing in the atmosphere.

But one of the side eects of the phase-out has been the

introducon of hdrouorocarbons (HFCs) as a replacement

for ozone-damaging chemicals in man applicaons. While

HFCs do not deplete the ozone laer, man are potent

greenhouse gases. Hence, HFCs represent a crucial link

between protecng the ozone laer and protecng climate.

The purpose of this UNEP report is to provide a brief

snthesis of exisng knowledge about HFCs, in parcular

the links between climate change, ozone depleng

substances and HFCs. The authors draw on previous reports

b internaonal bodies including: the IPCC/TEAP Special

Report on Safeguarding the Ozone Laer and the Global

Climate Sstem; the WMO/UNEP Scienc Assessment

Panel reports; WMO/UNEP Snthesis reports; UNEP/TEAP

reports; and other UNEP reports, as well as peer-reviewed

publicaons that have emerged since the publicaon of

these reports. This chapter reviews the benets of the

Montreal Protocol as a mechanism for protecng the ozone

laer. Chapter 2 reviews the climate benets of the phase-

out of ozone depleng substances; Chapter 3 discusses the

contribuon of HFCs to climate forcing, now and under

dierent future scenarios; and Chapter 4 examines the

alternaves to high-GWP HFCs.

The Montreal Protocol has led to great progress in phasing out important ozone depleng substances, including CFCs,

HCFCs, halons, and a number of other chemicals containing chlorine and bromine.

The Protocol is working as intended and expected. The depleon of the stratospheric ozone layer has been curtailed and

the ozone layer is expected to recover to its 1980 levels during this century.

But a parcular side eect of implemenng the Protocol merits aenon. As a result of phasing out ozone depleng

substances, HFCs have been introduced as replacements in many applicaons and are now nding their way to the

atmosphere.

HFCs vary signicantly in their ability to inuence climate; whereas some have low GWPs of less than 20, others are

potent greenhouse gases with GWPs of thousands to tens-of-thousands. Given the fact that the GWP of the current mix of

HFCs is about 1600, there is concern that HFCs could signicantly inuence climate in the future if they connue to increase.

1. 1 The Montreal Protocol has successfully

protected the ozone layerChlorouorocarbons (CFCs), hdrochlorouorocarbons

(HCFCs), halons, and other ozone depleng substances

(ODSs) are recognized as the main cause of the observed

depleon of the ozone laer and of the ozone hole (WMO

2011). The 1985 Vienna Convenon for the Protecon

of the Ozone Laer and the 1987 Montreal Protocol

on Substances that Deplete the Ozone Laer formall

recognized the signicant threat that ODSs posed to the

ozone laer and human health, as well as other potenal

eects, such as changes in climate.

Moreover, the Protocol and its subsequent Amendmentsand Adjustments provided mechanisms for the reducon

and phase-out of producon and consumpon of ODSs.

This was a major task because ODSs were once used in

large quanes for refrigeraon, air-condioning, re

exnguishing, and as solvents, propellants, fumigants,

and foam blowing agents. But the Protocol, together

with naonal regulaons and acons b companies and

consumers, was successful in substanall decreasing

the producon, consumpon and emissions of ODSs.

The observed atmospheric concentraons of most CFCs,

halons, methl chloroform and several other ODSs, are

indeed decreasing as expected from the Protocol andscienc understanding of the workings of the atmosphere

(Figure 1.1) (WMO 2011).

moNtREAl PRotoCol ANd ozoNE lAyER PRotECtioN HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyER 13


16/4014 HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyERmoNtREAl PRotoCol ANd ozoNE lAyER PRotECtioN

1.2 The Montreal Protocol is gradually phasing

out ODSsUnder the provisions of the Montreal Protocol and itsAmendments and Adjustments, CFCs were scheduled to be

phased out in developed (non-Arcle 5) Countries/Pares

b 1996 and in developing (Arcle 5) Countries/Pares

b 2010, with small allowances for special exempted

uses. The rst phase of the CFC phase-out ulized both

not-in-kind alternaves (products or technologies that

can substute for applicaons that require ODSs) and

drop-in replacements (chemicals that can be used in

exisng equipment with ver lile or no modicaons to

the equipment); the laer were mostl HCFCs and HFCs.

HCFCs have Ozone Depleon Potenals (ODPs) that are 10-50 mes smaller than CFCs and were classied under the

Protocol as transional substutes to be used during the

me it took to commercialize new ozone-safe alternaves

and replacements (Figure 1.2). HFCs have essenall zero

ODPs and are considered to be safe for the ozone laer.

In developed countries, the transion from using CFCs to

HCFCs started in the 1980s and was completed b around

2000. The transion from CFCs and/or HCFCs to HFCs

started in the 1990s and is now well underwa. This has

led to increased consumpon (Figure 1.3) and, as will be

seen in Chapter 3, increased emissions of HFCs. Developing

countries completed their CFC phase-out in 2010, inaccordance with the provisions of the Montreal Protocol.

Figure 1.1. Change in lower atmospheric abundance (in parts per billion, ppb) of the sum of chlorine

and bromine arising from ODSs as a result of the Montreal Protocol. The bromine abundance has

been mulplied b a factor of 60 to account for the 60-mes higher ecienc of bromine, relave to

chlorine, (on a per-atom basis) in depleng the stratospheric ozone laer. The hatched region is an

esmate of the atmospheric abundance of chlorine plus bromine that would have occurred without

the Montreal Protocol, assuming a 23% increase in annual producon of all ODSs (Figure based on

Velders et al., 2007)

The use of HCFCs has increased sharpl in developing

countries in the past decade, partl because the have

substuted for CFCs in some applicaons, but also as a

result of increased demand for products made with, or

containing, HCFCs. This increased use of HCFCs resulted in

an increase in their emissions, which is reected in their

atmospheric abundances (see Secon 3.1).

In response to connued concerns about the ozone laer

and increasing concerns about the global climate, the Pares

to the Montreal Protocol decided in 2007 to accelerate

HCFC phase-out. HCFC producon and consumpon in

Arcle 5 Pares (developing countries) are scheduled

to be frozen in 2013, followed b stepwise reducons,

with a virtuall complete phase-out b 2030. Non-Arcle5 Pares (developed countries) have agreed to a near

complete phase-out b 2020, with some countries aiming

for an earlier date. Thus, it is expected that almost all HCFC

producon and consumpon for emissive uses, i.e., uses

where the substance can escape into the atmosphere, will

cease b 2030.1 In specifing the accelerated HCFC phase-

out, Decision XIX/6 of the Montreal Protocol encouraged

Pares to promote the selecon of alternaves to HCFCs

that minimize environmental impacts; in parcular impacts

on climate, as well as meeng other health, safet and

economic consideraons. It is likel that this phase-out of

HCFCs will use HFCs, at least to some degree.

1. With the excepon of feedstock, process agents and other uses exempted under the Montreal Protocol

Lower atmospheric Cl+Br

1950 1970 1990 2010 2030 2050

Year

0

2

4

6

8

10

Without MontrealProtocol

LowerAtmosphericCl+Br(PPb)

Natural CH3Br and CH3Cl

CFCs, Halons, Others

HCFCs


17/40moNtREAl PRotoCol ANd ozoNE lAyER PRotECtioN HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyER 15

Figure 1.2. Flow diagram of ODS phase-out process. The rst stage involved the ulizaon of HCFCs (which are

less potent ozone depleng substances) as drop-in replacements for CFCs, and also encouraged the use of not-

in-kind alternave chemicals and technologies (see glossar). Subsequent stages included replacing CFCs and

HCFCs with other chemicals such as HFCs, with the eventual aim of developing chemicals and technologies that

are ozone-laer-safe and also benign to climate. The potenal benets of replacing high-HFCs are discussed in

this report.

Figure 1.3. The transion in global consumpon (b mass, in kilotonnes per ear), from CFCs to

HCFCs and to HFCs, their non-ozone depleng substutes. The data for CFCs and HCFCs is based on

consumpon reported to UNEP. The HFC data is from Velders et al (2009) and is based on emissions

derived from observed atmospheric abundances and reported producon data from the Alternave

Fluorocarbons Environmental Acceptabilit Stud (AFEAS). It is evident that the increase in HFC

usage is concomitant with the decrease in CFC consumpon.

Phased outby Montreal

Protocol

Ozonedepleng

Influencesclimate

Transional substutesfor CFCs/Being phased out

by Montreal Protocol

Less Ozonedepleng

Influencesclimate

Substutes forCFCs

Safe forozone layer

Potenal to Influenceclimate in future

Substutes forCFCs

Safe forozone layer

Minimal Influenceon climate

CFCs HCFCs

Minimal Impact on

Ozone and Climate

High-GWP

HFCs

Low-GWP

HFCs

HFCs Alternate technologiesand substutes with

no influence on

climate

Safe forozone layer

No Influence onclimate

HCFCs

CFCs

HFCs

1200

1000

800

600

400

200

0

Consumpon(ktonnesperyear)

Consumpton

1950 1960 1970 1980 1990 2000 2010

Year


18/4016 HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyERmoNtREAl PRotoCol ANd ozoNE lAyER PRotECtioN

1.3 The Montreal Protocol is working asexpected and intendedThe global emissions of CFCs and man other ODSs peaked

in the late 1980s and have decreased ever since. The

corresponding abundances of most ODSs in the atmosphere

peaked slightl later in the 1990s or 2000s (as expected)

and have since decreased. In 2010, total ODS emissions,

weighted b their ODPs, were about 25% of the peak in

the 1980s. Without the Montreal Protocol, ODS emissions

would have connued to increase from their peak in 1988

and could have almost doubled b 2010.

There is emerging evidence that the stratospheric ozone

laer is responding to these changes in ODSs and beginningto recover to its 1980 state. Current knowledge suggests

that the ozone laer will return to its 1980 levels towards

the middle of the 21s centur and that the ozone hole will

disappear later in the 21s centur. It is clear that adopng

the Montreal Protocol has avoided large, and possibl

catastrophic, damage to the ozone laer (WMO 2011).

In summar, the Montreal Protocol has avoided a:

Connued increase in ODS emissions;

Connued build up of ODSs in the atmosphere;

Connued depleon of the ozone laer and an

expanding ozone hole.

2. The snthesis in this report covers all HFCs apart from HFC-23. See Box 1 for further informaon.

This success was accomplished b using not-in-kindchemicals and technologies, as well as substutes that

were much less potent ozone depleng substances. The

ulizaon of HFCs has contributed to the success of the

Montreal Protocol.

1.4 HFCs are substutes for ODSsHFCs2 have been introduced into commercial use largel

because the have proven to be eecve substutes for

ODSs. The do not deplete the ozone laer and are suitable

for use in applicaons where CFCs and HCFCs were used.

These chemicals have no known natural sources. Thus, HFCs

are present in the atmosphere because the were used tocompl with the provisions of the Montreal Protocol.

HFCs have found widespread use in various applicaons.

The are used in refrigeraon and air-condioning

equipment in homes, other buildings and industrial

operaons (~55% of total HFC use in 2010, expressed in

Co2eq) and for air-condioning in vehicles (~24%). Smaller

amounts are used for foam products (~11%), aerosols

(~5%), re protecon sstems (~4%) and solvents (~1%)

(Figure 1.4). The use of HFCs is increasing rapidl as a result

of global economic development and populaon growth.

Figure 1.4. Esmated global consumpon of HFCs b various sectors, expressed in CO2equivalent, for 1990,

2002 and 2010 (TEAP 2005, EPA 2010a). HFCs are predominantl used for the same industrial uses as the

CFCs and HCFCs which are subject to phase-out under the Montreal Protocol. The rapid growth in HFCs

aer 1990 is also clearl evident.

The published esmates used in this gure are signicantl higher (aer accounng for the dierence in

units) than those shown in Figure ES 1 and Figure 1.3. The dierences arise because of the was in which CO2

equivalent consumpon is calculated and because of the dierences in data sets used. We used dierentdata here in order to provide a me series for the sectoral breakdown. This sectoral informaon was not

available for the data in Figure ES 1 and Figure 1.3.


19/40moNtREAl PRotoCol ANd ozoNE lAyER PRotECtioN HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyER 17

3. GWP weighng is used rounely to evaluate the relave climate impact of emissions of various gases (by mass) and is the basis for greenhouse gas emission

targets under the Kyoto Protocol, which uses the 100-year GWP. In this report, we will also use the 100-year GWP. See Glossary for further explanaon.

4. This value is calculated using the amounts used, weighted by their GWP, for the various components of the current mix of HFCs (Based on Velders et al. (2009)).

1.5 Many HFCs are potent greenhouse gasesHFCs are greenhouse gases that trap infrared radiaon in

the atmosphere that would otherwise escape to space. The

abilies of all HFCs to absorb infrared is roughl similar to

that of CFCs and HCFCs, and is much greater than those of

Co2, methane, or nitrous oxide, on a per-molecule or per-

mass basis. However, HFCs var signicantl in their abilit

to inuence climate. Their diering abilit is mostl due to

dierences in their atmospheric lifemes, which determine

how much the accumulate in the atmosphere. HFCs with

lifemes greater than a few ears accumulate more in the

atmosphere (for the same annual emission) and have larger

climate consequences, while those with shorter lifemes

do not accumulate as much, and have less inuence onthe climate. HFCs with lifemes of several ears have large

Global Warming Potenals (GWPs)3. For example, HFC-

134a, with an atmospheric lifeme of approximatel 13

ears, has a GWP of 1370. In contrast, HFCs with ver short

lifemes (das to weeks) have low GWPs. For example,

HFC-1234f has a lifeme of approximatel 10 das and is

esmated to have a GWP of 4. Clearl, HFCs are not all the

same when it comes to their abilit to inuence climate.

Of concern, is the fact that the average GWP of the

current mix of HFCs being used is about 1600 4, meaning

that a kg of currentl used HFC has about 1600 mes the

eect on global warming as a kg of CO2.

HFC-23 is an important greenhouse gas. It is mostl

generated as a b-product during the manufacture of HCFC-

22. It is not included in this report, because this report

focuses on HFCs that are produced and used primaril as

ODS substutes. The charts and projecons presented in

this report are based on studies that esmate future HFC

emissions b extrapolang exisng trends in the use of HFCs

as ODS substutes. Hence, HFC-23 cannot be included inthe projecons, as its emissions would rel on a completel

dierent set of assumpons.

Nevertheless here is some background informaon about

HFC-23:

HFC-23 does not destro stratospheric ozone.

There is ver lile reported direct use of HFC-23. It has

limited industrial uses, including use in semiconductor

fabricaon, ver low temperature refrigeraon and in

specialt re suppressant sstems (Miller et al. 2010).

HFC-23 is a ver potent greenhouse gas with a 100-ear

GWP of 14,200 and an atmospheric lifeme of 222 ears.

This makes it one of the most potent greenhouse gases. HFC-23 is the second most abundant HFC in the atmosphere

aer HFC-134a, reaching about 22 ppt in 2009. Currentl,

HFC-23 contributes 25% to the climate forcing b HFCs

(WMO 2011).

It is esmated that the HFC-23 could contribute an annual

emission up to 0.35 Gt CO2

eq by 2035 that would lead to

a radiave forcing up to 0.01 w -2 by that me (Miller

and Kuijpers 2011). An alternave esmate suggests that,

if HFC-23 were to connue to be produced as a by-product

of HCFC-22 unl 2050, the annual emission could be 0.25 Gt

Co2

eq (Gschrey et al. 2010)

Currentl, the release of HFC-23 to the atmosphere in some

developed countries is restricted b naonal regulaons,

voluntar acons, and market incenves. Some HCFC-22

producon facilies in developing countries capture and

destro HFC-23 (nanced b carbon emission reducon

credits under the Koto Protocol Clean Development

Mechanism (CDM)). HFC-23 captured in CDM projects is

destroed b incineraon. The atmospheric abundance of HFC-23 has increased over

the past decade, as HCFC-22 producon has increased

(Montzka et al. 2010). These increases are likel due to the

producon of HCFC-22 in facilies that are not covered b

the Koto Protocols CDM projects. The increase in HFC-23

has not been proporonal to the producon of HCFC-22

since the implementaon of the CDM projects reduced

the HFC-23 releases. The globall averaged abundance is

increasing at a rate of about 4% per ear.

Although HCFC-22 producon is controlled for refrigerant

and other end uses and is scheduled for phase-out b

2040, its producon as a feedstock for the manufactureof other chemicals is not controlled under the Montreal

Protocol. (Montzka et al. 2010). Therefore, the unintended

emission of HFC-23 as a bproduct of HCFC-22 producon

is expected to connue beond 2040 unless restricted b

internaonal, naonal, or voluntar acons (Miller and

Kuijpers 2011). The future levels are, therefore, dicult

to esmate, and appropriate projecons are not currentl

available.

Box 1. HFC-23 and its role in forcing climate


20/4018 HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyER CLIMATE BENEFITS OF THE MONTREAL PROTOCOL

2.1 Acons under the Montreal Protocol have

reduced and avoided emissions of important

greenhouse gasesIt has been known since the pioneering work of Ramanathan

(1975) that ODSs are greenhouse gases, which contribute

to the radiave forcing of climate. As a consequence, the

phase-out of ODSs, under the Montreal Protocol, has had

the added benet of protecng the global climate.The eects of ODS emissions on climate can be evaluated

using two metrics: CO2equivalent (CO2eq) emissions, based

on the GWP-weighng of the emissions; and the radiave

forcing that is governed b the atmospheric abundances of

ODSs (IPCC/TEAP 2005; Velders et al. 2007; WMO 2011).

Using these metrics, ODS emissions can be compared with

anthropogenic CO2 emissions, derived from observaons

and future scenarios.

Although ODS emissions are much smaller than CO2

emissions, several ODSs signicantl inuence climate

because the are potent greenhouse gases with high

GWPs. The 100-ear GWPs of the principal ODSs, range

between 5 (methl bromide) and 11,000 (CFC-12), which isclearl much larger than that of CO2 (GWP of CO2 is dened

to be 1).

The annual contribuon of ODSs to equivalent CO2

emissions, inferred from atmospheric observaons,

peaked in 1988 at 9.4 Gt CO2eq per ear, a value slightl

less than half of global annual CO2 emissions at that me

(Velders et al. 2007; Figure 2.1). Aer 1988, the equivalent

Co2 emissions of ODSs fell sharpl, in contrast to increasing

Co2 emissions. B 2010, ODS emissions had declined b

around 8.0 Gt CO2eq per ear to 1.4 Gt CO2eq per ear

(Figure 2.1), or about 5% of CO2 emissions for that ear.

Without the Montreal Protocol, the ODS emissions couldhave reached 1518 Gt CO2eq per ear in 2010, about half

he Co2 emissions that ear (Velders et al. 2007). This is

about 1113 mes larger than their current level.

Chapter 2:

Climate benets of the MontrealProtocol

2.2 Acons under the Montreal Protocol have

reduced radiave forcing by ODSsThe contribuon of ODSs to radiave forcing, and hence

climate change, depends on the accumulaon of emied

ODSs in the atmosphere. Furthermore, the eect on the

climate sstem depends not onl on the radiave forcing

b the chemical of interest, but also on how that chemical

alters atmospheric abundances of other climate gases(indirect climate eects). The radiave forcing from ODSs

reached a value of 0.32 W m -2 around 2000 and remain

more or less constant since. At the same me, from 2003

to 2010, radiave forcing values for CO2 increased b

0.2 W m-2

Without the Montreal Protocol, the projected radiave

forcing b ODSs would have been roughl 0.65 W m -2 n

2010 (Velders et al. 2007). This would have been 35% of

the current forcing b CO2 of 1.8 W m-2, and would have

made the contribuon of ODSs, collecvel, to radiave

forcing second onl to CO2. The radiave forcing avoided

b reducing ODS emissions amounts to about 0.3 W m-2

in 2010. To understand the importance of this gure, this

avoidance is about one-h of the radiave forcing caused

b the increase of CO2in the atmosphere since the pre-

industrial era.

2.3 Some of the climate benets of the

Montreal Protocol have been osetThe direct climate benets of the Montreal Protocol,

discussed above, have been parall oset b several

factors:

First, when ozone-depleng substances are reduced,

the ozone laer recovers, and as a result, the level ofozone in the upper atmosphere increases. Since ozone is

also a greenhouse gas, this recover adds to the global

Since most ODSs are potent greenhouse gases, acons under the Montreal Protocol have had the posive eect of

reducing a main source of global warming .

The ODS phase-out has resulted in one of the largest reducons to date in global greenhouse gas emissions.


21/40CLIMATE BENEFITS OF THE MONTREAL PROTOCOL HFCs, Cl imAtE PRotECtioN ANd tHE ozoNE lAyER 19

Figure 2.1. Climate benets of the Montreal Protocol expressed b the decrease in CO2eq emissions

of ODSs (CFCs, halons, HCFCs, and others). The hatched regions show that, without the Montreal

Protocol, CFC and other ODS emissions would have connued to increase greatl aer 2010. The box

in the diagram also shows that the target for reducing emissions under the Koto Protocol from 1990

to 2010 was about 2 Gt CO2eq per ear, but emissions from ODSs dropped b about 8 Gt CO2eq per

ear during the same period. B 2010, the level of ODS emissions was small relave to CO2 essns

(from energ and industr). Figure adapted from Velders et al. (2007).

greenhouse eect. This process is esmated to oset the

direct climate benets of ODS reducons b about 20%5.Second, replacing ODSs with HFCs, man of which are

potent greenhouse gases, has led to an increase in radiave

forcing from HFCs (see Chapter 3). This eect is esmated

to oset the climate benets of the Montreal Protocol to

date b up to 10%.

These two factors combined have oset the direct

climate benets of the Montreal Protocol b up to 30%

(Velders et al. 2007).

In addion, the phasing out of ODSs has led to various

life ccle changes in technologies and the operaon of

technologies. These changes have not been quaned in all

applicaons, but some of these changes are likel to have

had an indirect eect on emissions of greenhouse gases

(see Secon 3.7). For example, refrigeraon equipment

that used CFCs has been replaced in some cases b more

energ ecient equipment with reduced total emissions

of greenhouse gases, and in other cases b less energ

ecient equipment, which ma increase emissions.

2.4 The climate benets of the Montreal

Protocol are greater than the Kyoto targetThe phase-out of ODSs under the Montreal Protocol

avoided an esmated 10 Gt CO2eq per ear emissions in

2010, taking into account the ODS emissions that could

have occurred in the absence of the Montreal Protocol, the

osets b ozone depleon and increases in HFC emissions.

This gure for 2010 is about ve mes greater than the

annual emissions reducon target for the rst commitment

period (2008-2012) of the Koto Protocol, esmated6 a

2 g Co2eq per ear (see Figure 2.1) (UNEP 2011) and is

one of the largest reducons to date in greenhouse gas

emissions. Thus, it is clear that the Montreal Protocol has

alread contributed signicantl to liming the radiave

forcing of Earths climate.

As noted earlier, HFCs that replaced CFCs or HCFCs

are also inuencing climate. Currentl, the contribuon

to climate forcing b HFCs is small, but it is expected

to increase greatl in the future, as will be discussed in

Chapter 3. It is precisel this projected increase that has

focused aenon on HFCs.

5. That is, the reducon of ODS emissions has avoided a radiave forcing of about 0.3 W m -2 in 2010 (see text). But the recover of the ozone laer has been

esmated to have increased radiave forcing b around 0.05 0.10 W m-2 (IPCC, 2007), or about 20% of 0.3 W m-2.

6.The adopted CO2 equivalent emissions reducon target for the rst commitment period of the Koto Protocol is -5.8%, corresponding to -0.97 Gt CO2eq perear b 20082012. Because most countries would normall have had increasing greenhouse gas emissions aer 1990, the emission reducon necessar

to achieve the agreed Koto target has been calculated from a business-as-usual scenario between the 1990 baseline and 20082012. Business-as-usual

projecons from UNFCCC have total greenhouse gas emissions of Annex-1 pares increasing b 6% (1.06 Gt CO2eq per ear) above the 1990 value b 2010

in the absence of the Koto Protocol. Therefore, an arguabl more realisc esmate of the greenhouse gas emission reducon achieved b meeng the rst

Koto Protocol target is the combinaon of the 5.8% decrease and 6% increase for a total of about 2 Gt CO2eq per ear.

0

10

20

30

40

Magnitude ofKyoto Protocolreducon target

2.0

1950 1970 1990 2010 2030 2050

Year

CO2eqemissions(GtCO2eqperyear)

CO2

ODSs Without

Montreal Protocol

HCFCs

CFCs, Halons, others


22/4020 HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyERHFCs ANd ClimAtE CHANgE

Chapter 3:

HFCs and climate change

3.1 The atmospheric abundances of HFCs are

increasing rapidlyAtmospheric observaons7 show that the abundance of

HFCs in the atmosphere is increasing rapidl (Figure 3.1):

HFC-134a increased b about 10% per ear from 2006 to2010, reaching 58 ppt in 2010. HFC-134a, used in mobile

air condioning and man other applicaons, has become

the most abundant HFC in the atmosphere;

HFC-125, used in refrigeraon and air condioning,

increased b more than 15% per ear from 2006 to 2010,

reaching 8 ppt in 2010;

HFC-143a, used in refrigeraon and air condioning,

increased b about 15% per ear from 2004 to 2008,

reaching 9 ppt in 2008.

Atmospheric observaons of other high-GWP HFCs,

(e.g., HFC-32, -152a, -365mfc, 245fa, -236fa and -227ea),have been reported to be increasing; although, their rate

of increase was 1 ppt/r in 2008 (WMO 2011). The rate

of atmospheric increase depends on both the emission

amount and the atmospheric lifeme of the HFCs.

3.2 Equivalent CO2 emissions of HFCs are sll

small compared to other emissions but are

increasing rapidlyThe emissions of high-GWP HFCs, as inferred from

observed atmospheric abundances, are increasing ver

rapidl at about 10-15% per ear (Figure 3.1). Theseincreases translate into equivalent CO2 emissions of HFCs

(excluding HFC-23) of 8-9% per ear from 2004 to 2008

(WMO 2011). However, the sum of HFC emissions in 2008

(0.39 0.03 Gt CO2eq per ear; weighted b direct, 100-

ear GWPs) is sll small compared to emissions of other

greenhouse gases such as CFCs (1.1 0.3 Gt CO2eq per

ear); HCFCs (0.74 0.05 Gt CO2eq per ear); N2O (~3 GtCo2eq per ear); CH

4(~9 Gt CO2eq per ear), and CO2 (from

fossil fuel combuson, ~31 Gt CO2eq per ear) (WMO

2011).

The recent growth in emissions of HFCs at 8-9% per ear

is notabl greater than the recent increases of about 4%

per ear in the case of CO2 and about 0.5% per ear in the

case of methane.

The Pares to the Montreal Protocol do not report the

producon and consumpon of HFCs to the UN. However,

developed (Annex 1) countries do report HFC emissions

data to the UN Framework Convenon on Climate Change.

But the reported emissions cannot be compared directlwith the global emissions in Figure 3.1 because the are

onl a subset of total global emissions.

3.3 The current contribuon of HFCs to

climate forcing is small but rapidly growingThe current contribuon of HFCs to direct climate forcing

is calculated to be approximatel 0.012 W m-2. Thus, the

contribuon from HFCs to date has been less than 1%

of the total climate forcing b other greenhouse gases.

However, the annual increase in HFC forcing in the past

few ears is signicant when compared to that of other

substances during the same period. During a 5-ear period,

7. Independent air sampling networks collect air at dierent locaons around the globe with a range of sampling frequencies; the provide consistent

results for a range of trace gases, including HFCs (WMO, 2011).

HFC emissions and their atmospheric abundances are rapidly increasing.

Without intervenon, HFC emissions in the future (say by 2050) could oset much of the climate benet achieved by the

Montreal Protocol.

HFCs vary in strength with regard to their inuence on climate. Some have short lifemes (less than a few months) and

low GWPs, and some have long lifemes (from several to tens of years) and high GWPs.


23/40HFCs ANd Cl imAtE CHANgE HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyER 21

1990 1995 2000 2005 2010

Year

0

10

20

30

40

50

60

Abundances(ppt)

HFC abundances

HFC -134a

HFC -143a

HFC -152a

HFC -125

Figure 3.1 Increase in global average observed atmospheric abundances (3.1a) in parts per trillion,

ppt and global annual CO2eq emissions per ear (3.1b) of four major HFCs. The emissions are

inferred from the observed abundances. Not shown is HFC-23, the second most abundant HFC in

the atmosphere with an abundance of about 22 ppt in 2009 (See Box 1). (Observed abundances

from Chapter 1 of WMO (2011) with updates from Advanced Global Atmospheric Gases Experiment

(AGAGE) data).

3.1a

3.1bCO2eq emissions

1990 1995 2000 2005 2010

Year

0.00

0.05

0.10

0.15

0.20

0.25

HFC-134a

HFC-125

HFC-143a

HFC-152a

CO

2eqemissions(G

tCO

2eqperyear)



from mid 2003 to mid 2008, total radiave forcing fromHFCs increased b about 0.006 W m-2, which was slightl

lower than the increase from HCFCs (0.008 W m-2), half

of the increase from N2O (0.012 W m-2), and larger than

the increase from methane (0.004 W m -2). These increases

in radiave forcing from HFCs can be compared to the

decrease of 0.008 W m-2 from other ODSs (mainl CFCs)

over the same period. However, the are sll relavel

small compared to the increase from CO2 (0.14 W m-2) over

this same period. The major concern with respect to HFCs

is not that the are currentl large climate forcing agents,

but that their contribuon to climate forcing is expected to

increase rapidl in the future, such that the could becomever signicant contributors under some scenarios. HFC

emissions scenarios and their implicaons for climate

forcing are discussed in the next secon.

3.4 Dierent types of future HFC emissions

scenarios have been constructedScenarios have been developed and published b various

authors to assess the potenal impact of future HFC

emissions on climate. The can be broadl divided into

non-intervenon and intervenon scenarios.

Non-intervenon scenariosNon-intervenon scenarios provide projected emissions up

to at least the middle of the 21s centur (usuall 2050).

The extrapolate historical and current technological

developments, and assume no targeted polic intervenon

to reduce emissions. The are guided mainl b assumpons

about economic and populaon growth. The projecons of

future HFC emissions and abundances summarized in this

report are based on non-intervenon scenarios developed

b Velders et al. (2009) and Gschre et al. (2011):

Velders et al. (2009) developed four scenarios based on

assumpons similar to those of IPCC-SRES ( IPCC 2000).With respect to growth rates in gross domesc product

(GDP) and populaon, but incorporated new informaon

about: (i) HCFC consumpon in developing countries,

and (ii) the replacement of HCFCs b HFCs in developed

countries. The scenarios have upper and lower ranges

that reect the range in IPCC-SRES scenarios for growth

in GDP and populaon.

Gschre et al. (2011) based their scenario on sector-

specic growth rates and emissions factors for all

relevant sectors in developed and developing countries.

Both the Velders et al (2009) and Gschre et al (2011)scenarios take into account the accelerated phase-out

schedules of HCFCs and the EU Mobile Air Condioning

Direcve (EC 2006). The scenarios dier in their

assumpons about growth rates in major HFC-consumingsectors. The upper range scenario of Velders et al. (2009)

is based on the growth rates in the IPCC-SRES A1 scenario

and the lower range scenario of the A2 scenario, while the

Gschre et al. (2011) scenario is based on a combinaon

of the IPCC-SRES A1 and B1 scenarios. The growth rates in

the laer scenario are therefore slightl lower than in the

upper range scenario of Velders et al. (2009). The scenarios

also dier in projected market saturaon eects aer

about 2030, and dierent replacement paerns for ODSs

b HFCs and not-in-kind alternaves.

Intervenon scenarios

Intervenon scenarios are based on assumpons of future

potenal policies and measures to control emissions.

The discussions b the Pares to the Montreal Protocol

to promote the use of HCFC alternaves that minimize

the inuence on climate are also considered to be an

intervenon.

An HFC intervenon scenario was developed for IPCC/

TEAP (2005) and recentl updated (TEAP 2009a),

covering up to 2015 and 2020, respecvel. Because of

the short me periods covered b these scenarios, the

are not shown in Figures 3.2 and 3.3.

The new scenarios constructed for IPCC, the

Representave Concentraon Pathwas (RCPs), also

contain HFC emissions, but are based on an older

analsis of HFC growth. The also do not account for

the accelerated phase-out of HCFCs, nor the latest

growth in demand for HCFCs and HFCs. Therefore,

these scenarios, as for those of IPCC-SRES, are not

included in this report.

Hence, the gures and data presented in this report

have used informaon onl from recent non-intervenon

scenarios.

3.5 HFC emissions have the potenal to

become very large and at least partly oset

the climate benets of the Montreal ProtocolEmissions of HFCs are projected to connue increasing

under all non-intervenon scenarios (WMO 2011) and to

exceed the 1988-peak in ODS emissions (in tonnes, but not

equivalent CO2) b 2050. It is important to note that there

is inadequate knowledge about current trends in emissions

to determine which scenario will be more likel.

Figure 3.2 shows equivalent CO2emissions of HFCs up to

2050, according to the scenarios of Velders et al. (2009)

and Gschre et al. (2011). B 2050, the total HFC emissionsare 5.58.8 Gt CO2eq per ear under the Velders et al.

(2009) set of scenarios and 3.5 Gt CO2eq per ear under

the Gschre et al. (2011) scenario. HFC emissions clearl



have the potenal to become ver large. Emissions of HFCsare projected to exceed those of ODSs aer about 2020

(Figure 3.2) due primaril to growing demand in emerging

economies and increasing populaons.

As noted in Chapter 2, acons under the Montreal

Protocol led to a drop of ODS emissions between 1988 and

2010 equivalent to about 8.0 Gt CO2eq per ear. Without

intervenon, the increase in HFC emissions projected b

both Velders and Gschre will oset much of this climate

benet (Figure 3.2).

The projected HFC emissions can also be put into context

b comparing them to projected global CO2 essns n

2050. HFC emissions (on a CO2 equivalent basis) calculatedfrom data in Gschre et al. (2011) are about 7% of global

Co2 emissions in 2050 (not shown) and HFC emissions

projected b Velders et al. (2009) are about 9-19% of

hese Co2 emissions. Compared to the lower level of CO2

emissions expected in 2050 (not shown); under a scenario

of CO2 stabilizaon at 450 ppm (IPCC 2007), these gures

are 18%, and 28-45%, respecvel (Figure 3.2). Hence,

future HFC emissions ma also be substanal when

compared to future levels of CO2emissions.

3.6 The radiave forcing of HFCs is alsoprojected to signicantly increaseThe current contribuon of HFCs to radiave forcing is

relavel small, at about 0.012 W m-2. But b 2050, it could

be ten to thirt mes larger. Velders et al. (2009) esmate

an increase to 0.250.40 W m-2. The authors of this report

calculate a radiave forcing of 0.10-0.20 W m-2 due to HFC

emissions for the Gschre scenario.8 The upper range value

of 0.4 W m-2 is about one-quarter of the expected increase

in radiave forcing due to the buildup of CO2 from 2000

to 2050 according to the IPCC-SRES scenarios (Figure.3.3);

and 50-130% of the expected increase in forcing from other

Koto greenhouse gases. In a further comparison, the HFC

radiave forcing in 2050 (not shown) of 0.25-0.40 W m -2

corresponds to 712% of the CO2 values. This projected

HFC radiave forcing in 2050 is therefore equivalent to

613 ears of radiave forcing growth due to CO2 n he

2050 me frame.

The increase in HFC radiave forcing from 2000 to 2050

can also be compared to the radiave forcing corresponding

to a 450 ppm CO2 stabilizaon scenario. The reducon in

Figure 3.2. The decrease in CO2 equivalent emissions of ODSs (CFCs, halons, HCFCs, and others) (line

designated as ozone depleng substances) ma be oset b the projected increase in their non-

ozone depleng substutes (HFCs) (lines designated as HFC scenarios). The HFC scenarios shown

are the upper and lower (broken and doed lines respecvel) scenarios of Velders et al. (2009) and

the scenario (solid line) of Gschre et al. (2011). Shown for reference are emissions for the range of

global CO2 emissions from the IPCC-SRES scenarios (IPCC 2000; 2001) (gre shaded area), and for a

450 ppm CO2 stabilizaon scenario (IPCC 2007) (gre broken line) (The CO2 emissions depicted for

19502007 are reported emissions from fossil fuel use and cement producon). The HFC intervenon

scenario from TEAP (2009a) onl covers the period up to 2020, and is not shown because it would

not be visible. The emissions of the TEAP (2009a) scenario are 0.8 Gt CO2eq per ear in 2020; about

equal to the Gschre et al. (2011) scenario and slightl below the Velders et al. (2009) scenarios.

(Figure based on WMO 2011).

8. The radiave forcing was calculated using data from Gschre et al. (2011).

0

10

20

30

40

CO

2e

qemissions(GtCO

2e

qperyear)

1950 1970 1990 2010 2030 2050

Year

CO2eq emissions

Ozone Depleng

Substances

CO2

IPCC-SRES

CO2 rangeStabilizaon of

CO2 at 450ppm

HFC scenarios

Observaons Scenarios



radiave forcing necessar to go from a business-as-usual

scenario (as in IPCC-SRES, Figure 3.3) to such a stabilizaon

scenario is of the same order of magnitude as the increase

in HFC radiave forcing. In other words, the benets of

going from a business-as-usual pathwa to a pathwa in

which CO2 stabilizes at 450 ppm can be counteracted b

projected increases in HFC emissions.

There is, of course, inherent uncertaint in all projecons

about future levels of HFCs.

3.7 HFC emissions also have indirect climate

eects

In the preceding scenarios, onl the direct contribuonto climate forcing due to HFC and ODS emissions is

considered. But as noted in Secon 2.3, the use of HFCs

and halocarbons ma have secondar eects on climate

forcing. For example, thermal insulang products in

buildings and appliances reduce energ consumpon and

thereb tend to reduce emissions, whereas refrigeraon

and air-condioning sstems consume energ over their

lifemes and ma tend to increase emissions. A full

evaluaon of the total climate forcing (both direct and

indirect), resulng from the global transion awa from

CFCs and HCFCs toward HFCs, would require consideraon

of lifeccle CO2 emissions of all associated halocarbon, non-halocarbon, and not-in-kind alternaves (IPCC/TEAP 2005).

A comprehensive and detailed evaluaon of this kind has

not been carried out to date.

3.8 Dierent HFCs have dierent atmosphericlifemes and vary in their ability to inuence

climateIt is important to note that not all HFCs have the same

inuence on climate. As a group of gases, their inuence

varies signicantl (see secon 1.5). Their relave inuence

on climate is mostl due to dierences in their atmospheric

lifemes, which determine how much the accumulate in

the atmosphere. In general, the shorter the lifeme, the

lower the accumulaon in the atmosphere (for the same

annual emission), and the lower the GWP. HFCs with

shorter lifemes will also be removed more quickl from

the atmosphere, which means that their inuence onclimate will also diminish quickl once emissions cease.

Conversel, the longer the atmospheric lifeme, the

bigger is their inuence on climate. Full saturated HFCs

(for example, HFC-32, HFC-125, HFC-134a, HFC-143a,

HFC-152a) have lifemes ranging from 1 to 50 ears

(WMO 2011). Accordingl, their GWP for a 100-ear me

horizon also ranges greatl from 100 to 5,000 (Table 3.1).

Unsaturated HFCs (also referred to as hdrouoro-olens,

HFOs) have shorter atmospheric lifemes in the order of

das to weeks. Consequentl their GWPs (100-ear) are

around 20 or less.

At present, a few low-GWP HFCs (with lifemes less thana few months) are being either phased in or proposed as

substutes for HCFCs and some of the high-GWP HFCs

(with

Figure 3.3. Projected increase in radiave forcing of HFCs. The increase is signicant when compared

to the increase in radiave forcing from CO2 since 2000. For HFCs the upper range scenario of Velders

et al. (2009) is shown. The change in radiave forcing for CO 2 is from the IPCC-SRES scenarios and

for a 450 ppm CO2 stabilizaon scenario (IPCC 2007). Data were not available for a radiave forcing

calculaon for the Gschre et al. (2011) scenario, but the radiave forcing from this scenario isesmated to be 0.1 to 0.2 w -2 in 2050. (Figure based on Velders et al. 2009).

2.0

1.5

1.0

0.5

0.0

Changeinradiatveforcing(Wm

-2)

Change in radiatve

forcing since 2000

2000 2010 2020 2030 2040 2050

Year

SRES CO2 range

Stabilizaon ofCO2 at 450 ppm

Upper range

HFC scenario



Substance Lifeme (years) ODP GWP(20-yr) GWP(100-yr)

Chlorouorocarbons

CFC-11 45 1 6,730 4,750

CFC-12 100 1 11,000 10,900

CFC-113 85 0.8 6,540 6,130Hydrochlorouorocarbons

HCFC-22 11.9 0.055 5,130 1,790

HCFC-141b 9.2 0.11 2,240 717

HCFC-142b 17.2 0.065 5,390 2,220

Hydrouorocarbons (saturated)

HFC-32 5.2 2,470 716

HFC-41 2.8 377 107

HFC-125 28.2 6,290 3,420

HFC-134a 13.4 3,730 1,370

HFC-143a 47.1 5,780 4,180

HFC-152a 1.5 468 133

HFC-161 0.3a 43a12

a

HFC-227ea 38.9 5,480 3,580

HFC-245fa 7.7 3,410 1,050

HFC-365mfc 8.7 2,670 842

HFC-43-10mee 16.1 4,170 1,660

Hydrouorocarbons (unsaturated)

HFC-1234f 10.5 das 4

trans-HFC-1234ze 16.4 das 7

Table 3.1 Range of lifemes, ODPs, and GWPs (20-ear and 100-r me horizon) of major ozone depleng substances and HFCs

considered in this report (WMO, 2011).

a From IPCC (2007)

(with lifemes from several to tens of ears). Examplesinclude: HFC-1234f as a substute for the refrigerant HFC-

134a; HFC-161 as substute for the refrigerant HCFC-22;

and trans-HFC-1234ze as a substute blowing agent for

some thermal insulang foams (see Chapter 4). Some of

these low-GWP HFCs are so short-lived that the conceptof GWP ma not be applicable to them (WMO 2011).9 Fr

the purpose of comparison, the are esmated to be a

hundred to a thousand mes less potent as greenhouse

gases as the substances that the are expected to replace.

9. A 100-ear me horizon is oen used when comparing the climate forcing of non-CO2 greenhouse gas emissions relave to that of CO2. For emissions

of substances with shorter lifemes compared to the persistence of CO2 in the atmosphere (~ 100 or more ears), the climate forcing signicance is highl

sensive to the me-horizon assumed. Therefore, other me horizons ma be used depending on the me horizon of the impacts considered. Also, the use of

GWPs assumes that the substance is well mixed in the atmosphere. In realit, the global-mean lifemes and radiave eciencies of substances with lifemes

less than about half a ear are not well mixed and will depend on the locaon of emission.


28/40

3.9 A scenario in which only low-GWP HFCsare used has a low climate inuenceAs noted in secon 3.1, HFC radiave forcing is currentl

less than 1% of the total radiave forcing. Figure 3.4 shows

that if the current mix of HFCs (with an average lifeme

of 15 ears and an average GWP of 1600) were replaced

b low-GWP HFCs (with lifemes less than 1 month and

corresponding 100-ear GWPs less than about 20), their

contribuon to radiave forcing in 2050 would be less

than the current forcing, even for the upper range HFC

Figure 3.4. Radiave forcing for an upper range HFC scenario and for alternave scenarios with low-

GWP substutes. This gure shows that HFCs with shorter lifemes than the current HFC mix have a

smaller climate inuence in terms of lower radiave forcing. All curves are based on the assumpons

for growth in demand for the upper range HFC non-intervenon scenario of Velders et al. (2009)10

emissions scenario. Furthermore, it should be noted thatif the emissions of such short-lived HFCs were curtailed

in the future, their atmospheric abundances and possible

adverse climate eects would decrease quickl because

of their short lifemes. On the other hand, this scenario

does not take into account the feasibilit of using low-GWP

HFCs in all applicaons. In pracce, low-GWP HFCs are

onl one of several alternaves to high-GWP HFCs. These

alternaves are discussed in Chapter 4.

10.For illustrave purposes, the alternave scenarios assume that from 2015 onwards the same demand for HFCs is met b substutes with shorter lifemes

and consequentl lower GWPs. For the substutes, a molecular weight of 100 grams per mol is used and a radiave forcing per molecule of 0.2 W m -2 ppb-1,

both tpical values for commerciall used HCFCs and HFCs. An annual release from the bank of 13% is assumed, tpical for refrigeraon and air condioning

applicaons (WMO, 2011).

0.5

0.4

0.3

0.2

0.1

0.0

Radiatveforcing(Wm

-2)

Radiatve forcing

2000 2010 2020 2030 2040 2050

Year

Currentforcing

Upper range HFC scenarioLifeme 15 yr

3 yr

1 yr1 month

26 HFCs, ClimAtE PRotECtioN ANd tHE ozoNE lAyERHFCs ANd ClimAtE CHANgE


29/40

4.1 Methods for reducing the inuence

of high-GWP HFCs on climate have been

idenedHigh-GWP HFCs are used predominantl as ODS

replacements for refrigeraon and air-condioning

equipment, foam products and other applicaon (Secon1.4). The global demand for such products is increasing

with populaon growth and economic development.

Without intervenon, the increase in HFC emissions is

projected to oset much of the climate benet achieved b

earlier reducons in ODS emissions (Secon 3.5).

During the last decade, UNEP technical commiees and

government bodies have published informaon about

techniques that can be emploed to reduce the climate

inuence of high-GWP HFCs11. The describe best pracces

for reducing the emissions of HFCs, as well as alternave

technologies. Summing up these ndings, the alternave

technical opons for minimizing the inuence of HFCs onclimate fall into three categories:

Alternaves technologies12 with zero or low-GWPs that

replace the use of high-GWP HFCs include:

Alternave methods and processes (also called not-

in-kind alternaves). Commerciall used examples

include bre insulaon materials, dr-powder asthma

medicaon, and architectural designs that avoid the

need for air-condioners.

Chapter 4:

Alternaves to high-GWP HFCs

11. Examples include EC 2008; EPA 2006; EPA 2010a; FTOC 2011; GTZ 2008; GTZ 2009; IPCC/TEAP 2005; RTOC 2011; TEAP 1999; TEAP 2009; TEAP 2010ab;

UBA 2009; UBA 2011ab; UNEP 2010abc.12. Certain commercial technologies and products are idened for clarit and specicit. However, it is not intended as an endorsement of an specic

commercial product.

13. In contrast, the mix of high-GWP HFCs used at present has an average lifeme of 15 ears, based on tonnage used. The implicaons of this are explained

in Figure 3.4.

14. The terms alternaves and alternave sstems are used as abbreviaons for the three categories of low-GWP alternaves listed in Secon 4.1.

Non-HFC substances with low or zero GWPs.

Commerciall used examples include hdrocarbons (e.g.

R-290, R-600a), ammonia (R-717), carbon dioxide (R-

744), nitrogen, dimethl ether, and other substances.

Low-GWP HFCs. Several low-GWP HFCs (with lifemes

of less than a few months13

) are being developed andintroduced. Examples include HFC-1234f, HFC-1234ze

and HFC-1336mzz. These are discussed in Secon 3.8.

A number of studies have concluded that combinaons

of these techniques could achieve substanal reducons in

the consumpon and emission of high-GWP HFCs.

4.2 Low-GWP alternaves14 oer the

potenal to minimize the inuence of high-

GWP HFCs on climateAs shown in Figure 3.4, alternaves with lifemes less than

several months an

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