metrics and stabilization of the global average surface temperature

Chalmers University of Technology

Metrics and stabilization of the global average surface temperature

Daniel J.A. JohanssonDivision of Physical Resource Theory, Department of Energy and Environment


Gothenburg, Sweden.

UNFCCC workshop on common metrics

Bonn, Germany, 2012-04-03


Outline

• Emissions profiles• Global Cost Potential (GCP)• Global Temperature change Potential (GTP)• Cost-Effective Temperature Potential (CETP)


Stabilizing below 2ºC cost-effectively

UNEP, 2010, The Emissions Gap Report

GWP was not designed to facilitate the basket approach in a cost effective stabilization regime.

CO2 equivalent emissions using GWP-100


Global Cost Potential (GCP).

• Based on that a climate target should be met at lowest possible abatement cost.

• Based on optimizing Integrated Assessment Models (IAMs).


Optimizing Integrated Assessment Model

Economy & Energy module

Emissions

Climate module:Calculates concentrations, radiative forcing

and subsequent temperature response


Optimizing Integrated Assessment Model

Economy & Energy module

Emissions

Climate module:Calculates concentrations, radiative forcing

and subsequent temperature response

Objective:Minimize total NPV abatement costs to stabilize the temperature at 2°C

above the pre-industrial level

•Cost optimal emissions profiles compatible with this target

•Cost optimal emissions prices (taxes) needed to induce abatement


Global Cost Potential (GCP)

• Based on that a climate target should be met at lowest possible abatement cost.

• Based on optimizing Integrated Assessment Models (IAMs).

• The metric is the ratio of the cost-optimal price (tax) on emissions of a gas X to the cost-optimal tax on emissions of CO2.


Global Cost Potential (GCP)

Manne & Richels, 2001, An alternative approach to establishing trade-offs among greenhouse gases, Nature

2000 2200 2000 2100


GCP - Transparency and numerical models

• Optimizing IAMs are complex and far from transparent for most climate scientist, policy advisors and policy makers.

• Include a range of very uncertain parameters and uncertain structural relationships.


Global Temperature change Potential (GTP)

0

0,01

0,02

0,03

0,04

0,05

0,06

0 50 100 150 200 250 300 350 400 450 500

Tem

pera

ture

(mK)

Time (Year)

1 M ton CH4

100 M ton CO2

GTP for year t

)(

)(

2tT

tTtGTP

CO

X

GTP initially developed in: Shine K.P., Fuglestvedt J.S., Hailemariam K., Stuber N. , 2005, Alternatives to the Global Warming Potential for Comparing Climate Impacts of Emissions of Greenhouse Gases, Climatic Change


Comparison GCP and GTP for CH4

0

20

40

60

80

100

120

2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100

Time (year)

Rel

ativ

e va

luat

ion

of

CH

4 to

CO

2

GCPGTP

Results from runs with the MiMiC model (Azar, Johansson & Persson)

Relationship between GTP and GCP originally formulated in : Shine K.P., Berntsen T.K., Fuglestvedt J.S., Bieltvedt Skeie R., Stuber N., 2007, Comparing the climate effect of emissions of short- and long-lived climate agents, Philosophical Transactions of The Royal Society A


Cost-Effective Temperature Potential (CETP)

An approximation of GCP.

Includes:-physical information,

-an estimate of stabilisation year,

-discount rate.

Johansson, 2011, Johansson, 2011, Economics- and physical-based metrics for comparing greenhouse gases, Climatic Change.


CETP

0

0,01

0,02

0,03

0,04

0,05

0,06

0 50 100 150 200 250 300 350 400 450 500

Tem

pera

ture

(mK)

Time (Year)

1 M ton CH4

100 M ton CO2

CETP for year t

The time integrated discounted temperature pulse beyond the target time year.

e-rτ=Discount factorr-discount rateτ -time

deT

deT

tCETPr

t

CO

r

t

X

·)(

·)(

2

Integrate and discount


Simple Carbon Cycle and Climate model ACC2

Tanaka et al., 2007, MPI Report;Tanaka et al., 2009, GRLTanaka et al., 2009, Climatic Change

Su

rface

Air T

em

pe

ratu

re C

ha

ng

e

DO

EC

LIM

(Krie

gle

r, 20

05

)

Em

ission

s of g

ree

nh

ou

se g

ase

s & re

late

d a

ge

nts

CH4 & N2O

SF6 & 29 Halocarbons

Tropos-/Stratospheric O3

Sulfate/Carbonaceous Aerosols (direct/indirect)

Stratospheric H2O

OH, NOx, CO, VOC

Atmospheric Chemistry

To

tal R

ad

iative

Fo

rcing

Carbon Cycle

Ho

oss e

t al. (2

00

1)

IRF

4-B

ox M

od

el

Atmosphere

Joo

s et a

l. (19

96

)IR

F 4

-Bo

x Mo

de

lOcean Uptake

Land Uptake

Pa

ram

ete

rizatio

n

Climate

Pa

ram

ete

rizatio

n (Jo

os e

t al., 2

00

1)

Temperature feedback

Max 2ºC above pre-industrial level

Minimizing NPV abatement cost


CH4 metric value in 2°C stabilization scenario

0

20

40

60

80

100

120

140

2000 2020 2040 2060 2080 2100

CH4

met

rics

Year

GWP5

GWP20

GWP100

GTP5

GTP20

GTP100

Tanaka K., Berntsen T.K., Fuglestvedt J.S., Johansson D.J.A., O’Neill B., 2012, [working title:] Evaluation of emission metrics under climate stabilization targets, Ongoing work.



0

20

40

60

80

100

120

140

2000 2020 2040 2060 2080 2100

CH4

met

rics

Year

GWP5

GWP20

GWP100

GTP5

GTP20

GTP100

CETP

GCP




0

20

40

60

80

100

120

140

2000 2020 2040 2060 2080 2100

CH4

met

rics

Year

GWP5

GWP20

GWP100

GTP5

GTP20

GTP100

GTPSTB

CETP

GCP



N2O metric value in 2°C stabilization scenario

150

200

250

300

350

400

2000 2020 2040 2060 2080 2100

N2O

met

rics

Year

GWP5

GWP20

GWP100

GTP5

GTP20

GTP100

GTPSTB

CETP

GCP



Importance of discount rateCH4

Johansson, 2011, Economics- and physical-based metrics for comparing greenhouse gases, Climatic Change.


Importance of discount rateN2O


Conclusion• GWP was not constructed to facilitate the implementation of cost-effective

climate stabilization regime…• … although it has enabled the implementation of the basket approach.• Using cost effective trade-off ratios (Global Cost Potential - GCP) instead

of GWP could enhance the cost-effectiveness of a stabilization regime…• … but one would then depend on complex and uncertain optimizing

IAMs.• CETP approximate GCP well under a range of assumptions.• Neither GTP, CETP and GCP take into account climate effects in the

short term.• CETP and GCP do to take into account climate effects in the long-term,

beyond stabilization, while GTP does not.


THANK YOU!Questions, comments?


Additional cost of meeting the 2°C limit when using GWP-100 as compared to GCP

Based on: Johansson, Persson & Azar, 2006, The cost using Global Warming Potentials, Climatic Change

• The use of GWP-100 would set a too high price on CH4

(short lived gases) years far from when stabilization occur, while the opposite hold for years close to when stabilization occur.

• The cost of of using GWP-100 is very approximately about 5% of Net Present Value (NPV) abatement cost.

metrics and stabilization of the global average surface temperature

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