Martin Manning and Greg Bodeker

National Institute of Water and Atmospheric Research

Presented at ‘Expert meeting on assessment of contributions to climate change’, Bracknell, UK, 25 to 27 September 2002

EmissionsIssues: Regional mismatches between

EDGAR and SRES. Treatment of bunker fuels. Discrepancies between EDGAR

and Marland et al. fossil fuel CO2 emissions.

Discrepancies between Stern and Kauffman CH4 emissions used in Phase 1 and EDGAR.

Suggests need for re-examining emissions data before their use in attribution.

0

5

10

15

20

25

30C

O2

em

iss

ion

s (

Pg

C/y

ea

r)

0

0.2

0.4

0.6

0.8

CH

4 e

mis

sio

ns

(P

gC

H4/

ye

ar)

0

3

6

9

12

15

N2O

em

iss

ion

s (

Tg

N/y

ea

r)

1750 1800 1850 1900 1950 2000 2050 2100Year

Unattributed: linearfrom 0 in 1750

EDGAR database SRES A2 ASFALMASIAREFOECD90

Emissions Concentrations

For CO2

Use pulse response model of Joos et al. (1996) with separate response functions for ocean and biosphere uptake processes.

No temperature feedbacks on sea water CO2 solubility

Only parameter adjusted is effective air-sea exchange coefficient; used 0.07/year rather than 1.04/year.

Emissions Concentrations

Atmosphere

Biosphere

Ocean

Fab

Fba

Fao

0 10 20 30 40 50Years

Amount of carbon remaining in surface layer after an input from the atmosphere.

0 10 20 30 40 50Years

Return flux of carbon to the atmosphere after input from the atmosphere.

Emissions Concentrations

Issues for carbon cycle modelling

Regional attribution of changes in CO2 concentrations to changes in regional emissions in the presence of non-linearities we use the marginal attribution approach of Enting et al. (1998) and attribute the change each year in pCO2 or NPP according to the attributed change in the driving factors.

Emissions Concentrations

For CH4 and N2O

Integrated the ODE for time rate of change of CH4 and N2O using a fixed methane lifetime of 10 years and a fixed N2O lifetime of 114 years.

ConcentrationsRadiative Forcing

Components for CO2, CH4, N2O and sulfate aerosol assumed to be additive.

RFCO2 = 5.35 ln[ pCO2/ pCO2(0) ]

RFCH4 = 0.036 ([CH4] - [CH4(0)] ) + {CH4 & N2O term}

RFN2O = 0.12 ([N2O] - [N2O(0)] ) + {CH4 & N2O term}

RFsul = f Esul i.e. proportional to emissions

Again, non-linear relationships mean that for attribution of forcing to each source region we use the marginal approach contibution to changes in drivers determines contribution to changes in responses.

Temperature Change

Radiative Forcing

Coefficients for ls and s from fit to HadCM3 stabilisation experiment as provided on web page by Jason Lowe (UKMO).

2000 2050 2100

0

1

2

3

4

5

Tem

per

atu

re c

han

ge

(oC

)

A L MA S IAR E FO E C D 9 0U n a ttr ib u ted

2000 2050 2100

0

20

40

60

80

100

% o

f to

tal w

arm

ing

2000 2050 2100

0

1

2

3

4

5

Tem

per

atu

re c

han

ge

(oC

)

A L MA S IAR E FO E C D 9 0U n a ttr ib u ted

2000 2050 2100

0

20

40

60

80

100

% o

f to

tal w

arm

ing

ResultsCase I

Attribution of emissions to regions from 1890 to 2100

Case IIAttribution of emissions to regions from 1890 to 2000

Outstanding issues

Treatment of emissions pre-1890.

Inadequacies caused by constant CH4 lifetime.

Treatment of bunker fuels.