SAP report on GWPs in Group I of Annex A, C and F

SAP co-chairs: David W. Fahey, Paul A. Newman,

John Pyle, Bonfils Safari SAP members

Background •  Kigali Amendment comment, “204. …...the Scientific

Assessment Panel needs to begin the work .. to provide the Meeting of the Parties with the information it would require to adjust the global-warming potentials of the substances in Group I of Annex A, Annex C and Annex F …and .. it should report on its progress …to the Open-ended Working Group at its 39th meeting.”

•  HCFC GWPs are necessary for calculating the Kigali amendment baselines for the HFC phase down

Outline

•  What is a GWP? •  Where do the Annex C and F GWP’s

come from? •  How will these GWPs be updated?

Global Warming Potential •  A GWP is a metric for evaluating the climate forcing of a

substance relative to CO2 over a specified period. •  The global radiative forcing of 1-kg of a particular gas with

respect to 1-kg of CO2 over a time-period (e.g., 100 years). •  GWP 100-yr, from Table 5A-1 in [WMO, 2014]

–  CO2 = 1 –  CH4 = 28 –  N2O = 265 –  CFC-11 = 4,660 –  CFC-12 = 10,200

•  Developed for the first IPCC assessment [Derwent, Rodhe, and Wuebbles, 1990] –  Very similar to the ozone depletion potential (ODP), but for

comparing climate impacts

Group I Annex C The following table shall

replace the table for Group I in Annex C to the Protocol:

NotethemissingGWPvaluesformanysubstances.ThesearefromtheScien;ficAssessmentofOzoneDeple;on:2006[WMO,2007]

NotespecificallythoseHCFCsmissingGWPsinthe1989HCFCdataforA2Par;esand2009/2010HCFCdataforA5Par;es:

HCFC-121HCFC-122HCFC-133HCFC-141HCFC-142HCFC-225

BlankentryassumedZero

Current GWP Estimates from WMO [2014] Table 5A-1

How do we calculate the Global Warming Potential?

•  The lifetime of the gas (τ) •  Its radiative efficiency (Reff) •  These rely on laboratory

measurements (kinetics, infrared spectra, etc) and/or empirical models.

We need to know:

GWPs have changed because the science and atmosphere are changing

2014 2010 2006 2002 1998 1994 1990 1400

1600

1800

2000

HC

FC-2

2 G

WP

100-

y

TheHCFC-22GWPchangesbecause:1)  Thereferencelife@mechanges2)  LabmeasurementsoftheIRabsorp@onareimproved3)  TheabsoluteglobalwarmingofCO2changes(AGWP)

AnnexCcurrentvalue

WMOIPCC

A.  HCFC-22 lifetime increaseB.  Small change of IR spectrumC.  Large decrease of CO2 AGWP

How do we calculate the Global Warming Potential?

IR absorption spectra, radiative efficiency C

ross

Sec

tion

(10-

18 c

m2 m

olec

ule-

1 )

010

200

1

2

Wavenumber (cm-1)500 1000 1500

Calculated spectraMeasured

Conformers: color codedPopulation weighted

HCFC-225ca (CHCl2CF2CF3)

Molecules like HCFC-225ca are important

climate gases because they absorb in the

atmospheric window

Papanastasiou,etal.[2017],NOAA

Global Warming Potentials have been estimated for HCFCs in Annex C

Life@mes GWPs

“Hydrochlorofluorocarbons(HCFCs)OzoneDeple;onandGlobalWarmingPoten;alDetermina;on”DimitriosK.Papanastasiou,P.Marshall,andJ.B.Burkholder[2017],NOAA

•  Comprehensiveevalua;onofC1,C2,andC3HCFCs,for274compounds,includingallisomersandstableconformers

•  Life;me,ODP,GWP,GTP•  Thispaperwillbesubmi`edtoapeer-reviewedjournalthissummer.RE and Global Warming Potential (GWP) Results

C1

C2

C3

Increasing H

aa CHF2CCl2CF3

ba CHClFCClFCF3

bb CHF2CClFCClF2

ca CHCl2CF2CF3

cb CHClFCF2CClF2

cc CHF2CF2CCl2Fda CClF2CHClCF3

ea CClF2CHFCClF2

eb CCl2FCCHFCF3

RE range is a factor of 2 (0.15 – 0.3)

GWPs are isomer dependent• Reflects RE and Lifetime factors

Hodnebrog et al. (2013) RE method C1 C3

Increasing H

C2

Large range of GWP values (10 – 5500)

HCFC-225 Isomers

10

Life@mes GWPs

HCFC-235faCClF2CH2CF3HCFC-141b

C2H3Cl2F

Papanastasiou,etal.[2017],NOAA

The 2018 SAP Assessment will provide a listing of revised GWPs covering the Annex substances

•  Scientific Assessment of Ozone Depletion: 2018 authors selected, and the 1st draft is being written. –  The completed report will be available in Dec. 2018

•  NOAA’s GWP revisions and new estimates will be discussed in Chapter 6: “Scenarios and information for policymakers” –  Lead Authors: Lucy Carpenter and John Daniel –  Co-authors: T. Hanaoka, J. Hu, K. Law, S. Tilmes, T. Wallington, H.

Walter-Terrinoni, D. Wuebbles, A. R. Ravishankara –  Values to be tabulated in Assessment Appendix

•  The uncertainty of GWP values is ~40%. Better accuracy could be achieved with dedicated laboratory experiments which are time consuming and expensive but could be carried out for key substances

Thank you for your attention