Chalmers University of Technology
UNFCCC workshop on common metrics
Bonn, Germany, 2012-04-03
Daniel J.A. Johansson
Division of Physical Resource Theory, Department of Energy and Environment
Chalmers University of Technology
Gothenburg, Sweden.

Chalmers University of Technology
• Emissions profiles
• Global Cost Potential (GCP)
• Global Temperature change Potential (GTP)
• Cost-Effective Temperature Potential (CETP)

Chalmers University of Technology
Stabilizing below 2 ºC cost-effectively
CO
2 equivalent emissions using GWP-100
GWP was not designed to facilitate the basket approach in a cost effective stabilization regime.
UNEP, 2010, The Emissions Gap Report

Chalmers University of Technology
• Based on that a climate target should be met at lowest possible abatement cost.
• Based on optimizing Integrated Assessment Models
(IAMs).

Chalmers University of Technology
Economy & Energy module
Emissions
Climate module:
Calculates concentrations, radiative forcing and subsequent temperature response

Chalmers University of Technology
Objective:
Minimize total NPV abatement costs to stabilize the temperature at 2°C above the pre-industrial level
Emissions
• Climate module:
• Calculates concentrations, radiative forcing and subsequent temperature response

Chalmers University of Technology
• 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 CO
2
.

Chalmers University of Technology
2000
2200 2000
Manne & Richels, 2001, An alternative approach to establishing trade-offs among greenhouse gases, Nature
2100

Chalmers University of Technology
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.

Chalmers University of Technology
0,06
0,05
0,04
0,03
0,02
0,01
0
0
Global Temperature change Potential (GTP)
GTP for year t
1 M ton CH4
50 100 150
100 M ton CO2
350 400 450 500
GTP
 


T
X

T
CO
2
( t )
( t )
200 250
Time (Year)
300
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

Chalmers University of Technology
120
Comparison GCP and GTP for CH
4
100
80
60
40
GCP
GTP
20
0
2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100
Time (year)
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

Chalmers University of Technology
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 .

Chalmers University of Technology
0,06
0,05
0,04
0,03
0,02
0,01
0
0
CETP for year t
50
100 M ton CO2
Integrate and discount
1 M ton CH4
100 150 200 250
Time (Year)
300 350 400 450
The time integrated discounted temperature pulse beyond the target time year.
500
CETP
 
 t
 t





T
X
T
CO
2
(

(

) · e
) · e
 r
 r d
 d
 e -rτ = Discount factor r -discount rate
τ -time

Chalmers University of Technology
Simple Carbon Cycle and Climate model ACC2
Carbon Cycle Climate
Temperature feedback
Atmosphere Max 2 ºC above pre-industrial level
Minimizing NPV abatement cost
Land
Ocean
Uptake
Uptake
Atmospheric Chemistry
CH
4
& N
2
O
SF
6
& 29 Halocarbons
Tropos-/Stratospheric O
3
Sulfate/Carbonaceous
Aerosols (direct/indirect)
Stratospheric H
2
O
OH, NO x
, CO, VOC
Tanaka et al., 2007, MPI Report ;
Tanaka et al., 2009, GRL
Tanaka et al., 2009, Climatic Change

Chalmers University of Technology
CH
4 metric value in 2°C stabilization scenario
140
120
100
80
60
40
20
0
2000 2020 2040 2060 2080 2100
GWP5
GWP20
GWP100
GTP5
GTP20
GTP100
Evaluation of emission metrics under climate stabilization targets, Ongoing work.

Chalmers University of Technology
CH
4 metric value in 2°C stabilization scenario
140
120
100
80
60
40
20
0
2000 2020 2040 2060 2080 2100
GWP5
GWP20
GWP100
GTP5
GTP20
GTP100
CETP
GCP
Evaluation of emission metrics under climate stabilization targets, Ongoing work.

Chalmers University of Technology
CH
4 metric value in 2°C stabilization scenario
140
120
100
80
60
40
20
0
2000 2020 2040 2060 2080 2100
GWP5
GWP20
GWP100
GTP5
GTP20
GTP100
GTPSTB
CETP
GCP
Evaluation of emission metrics under climate stabilization targets, Ongoing work.

Chalmers University of Technology
N
2
O metric value in 2°C stabilization scenario
400
350
300
250
200
GWP5
GWP20
GWP100
GTP5
GTP20
GTP100
GTPSTB
CETP
GCP
150
2000 2020 2040 2060 2080 2100
Year
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.

Chalmers University of Technology
4
Johansson, 2011, Economics- and physical-based metrics for comparing greenhouse gases, Climatic
Change .

Chalmers University of Technology
2

Chalmers University of Technology
• 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.

Chalmers University of Technology

Chalmers University of Technology
Additional cost of meeting the 2°C limit when using
GWP-100 as compared to GCP
• The use of GWP-100 would set a too high price on CH
4
(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.
Based on: Johansson, Persson & Azar, 2006, The cost using Global Warming Potentials, Climatic Change