Metrics and stabilization of the global average surface temperature

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Metrics and stabilization of the global average
surface temperature
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.

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Outline

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

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Stabilizing below 2ºC cost-effectively
CO2 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
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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).

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Optimizing Integrated Assessment Model
Economy Energy module
Emissions
Climate module Calculates concentrations,
radiative forcing and subsequent temperature
response
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Optimizing Integrated Assessment Model

• Objective
• Minimize total NPV abatement costs to stabilize
  the temperature at 2C above the pre-industrial
  level
• Cost optimal emissions profiles compatible with
  this target
• Cost optimal emissions prices (taxes) needed to
  induce abatement

Economy Energy module
Emissions
Climate module Calculates concentrations,
radiative forcing and subsequent temperature
response
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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.

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Global Cost Potential (GCP)
2100
2200
2000
2000
Manne Richels, 2001, An alternative approach to
establishing trade-offs among greenhouse gases,
Nature
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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.

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Global Temperature change Potential (GTP)
GTP for year t
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
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Comparison GCP and GTP for CH4
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
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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.
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CETP
The time integrated discounted temperature pulse
beyond the target time year. e-rtDiscount
factor r-discount rate t -time
CETP for year t
Integrate and discount
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Simple Carbon Cycle and Climate model ACC2
Max 2ºC above pre-industrial level Minimizing
NPV abatement cost
Tanaka et al., 2007, MPI Report Tanaka et al.,
2009, GRL Tanaka et al., 2009, Climatic Change
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CH4 metric value in 2C stabilization scenario
Tanaka K., Berntsen T.K., Fuglestvedt J.S.,
Johansson D.J.A., ONeill B., 2012, working
title Evaluation of emission metrics under
climate stabilization targets, Ongoing work.
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CH4 metric value in 2C stabilization scenario
Tanaka K., Berntsen T.K., Fuglestvedt J.S.,
Johansson D.J.A., ONeill B., 2012, working
title Evaluation of emission metrics under
climate stabilization targets, Ongoing work.
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CH4 metric value in 2C stabilization scenario
Tanaka K., Berntsen T.K., Fuglestvedt J.S.,
Johansson D.J.A., ONeill B., 2012, working
title Evaluation of emission metrics under
climate stabilization targets, Ongoing work.
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N2O metric value in 2C stabilization scenario
Tanaka K., Berntsen T.K., Fuglestvedt J.S.,
Johansson D.J.A., ONeill B., 2012, working
title Evaluation of emission metrics under
climate stabilization targets, Ongoing work.
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Importance of discount rateCH4
Johansson, 2011, Economics- and physical-based
metrics for comparing greenhouse gases, Climatic
Change.
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Importance of discount rateN2O
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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.

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• THANK YOU!
• Questions, comments?

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

• 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.

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