Interim targets: Guideposts to reaching
long-term climate change goals
Brian O’Neill
International Institute for Applied Systems Analysis
Laxenburg, Austria

Contributors:
James Wang & Bill Chameides, Environmental Defense
Michael Oppenheimer, Princeton University
Annie Petsonk, Environmental Defense
Ilkka Keppo & Keywan Riahi, IIASA
Presented at the IIASA-RITE International Symposium
12 March 2007, Tokyo

Long-term Climate Change
Policy Goals
1992: Framework Convention
Objective: “...stabilization of greenhouse gas concentrations
concentrations in the atmosphere at a level that would
prevent dangerous anthropogenic interference with theclimate system.” “…within a time-frame sufficient to allow ecosystems toadapt naturally to climate change, to ensure that foodproduction is not threatened and to enable economic
development to proceed in a sustainable manner. ….”
Short-term Climate Change
Policy Goals
1997: Kyoto Protocol
Legally binding emissions reductions targets
for industrialized countries for 2008-2012

2001: Many details of flexible mechanisms
agreed to at COP 10 in Marrakech
2005: Entry into force

Dangerous interference:
Criteria for Concern, IPCC

Source: Smith et al., 2001, IPCC TAR WG2, Ch. 19.

ProblemWill be difficult (in the near future, impossible?)to agree on what level of climate change is“dangerous”
Meanwhile,

we may commit ourselves to potentially dangerous
levels of climate change we may commit ourselves to potentially dangerous
rates of climate change we lack policy signals to guide decisions with long time
horizons – exactly the kinds of decisions necessary formeeting long-term goals

Short-term policies (e.g., Kyoto Protocol) do not
sufficiently guard against these problems

Proposal: Interim (Mid-Century)
Concentration Targets

Based on O’Neill et al., 2005.

Proposal: Interim (Mid-Century)
Concentration Targets?

Based on O’Neill et al., 2005.

Proposal: Interim (Mid-Century)
Concentration Targets?

Based on O’Neill et al., 2005.

Proposal: Interim (Mid-Century)
Concentration Targets?
?

Based on O’Neill et al., 2005.

Interim Concentration Targets
Keep a range of century-scale targets feasible
while uncertainties are narrowed
Limit rates of climate change in the medium term
Better inform multi-decade planning horizons
May broaden grounds for agreement in policy
discussions
Would require periodic review and updating as
new information became available
Does not imply any single policy regime forachieving it

Interim Concentration Targets
Targets could take range of forms, fromweak to strong:
Evaluation framework for climate policy
proposals
 Informal aspirational goal(s) Formal targets under Convention/Protocolregime Integrating point for parallel policy regimes?

Why Concentrations?
Balances uncertainty in consequences withuncertainty in required mitigation activity
activities -> emissions -> concentrations -> climate change -> impacts

Easier to detect progress toward
concentration goal than temperature goal
Equivalent CO2 integrates across multiplegases

Why Mid-Century?
Psychologically tractable
Political precedents (GATT/WTO, SocialSecurity)
Long enough to affect rates of temperaturechange, short enough to constrain themConsistent with timescale of long-lived
capitalRelated Proposals or Analyses
Medium-term emissions goals by countries (e.g.,UK) or states (e.g., California)
Global emissions goals (Corfee-Morlot andHoehne, 2003; Pacala and Socolow, 2004)
Technology needs in medium term (Hoffert et al.,
2002; Pershing and Tudela, 2003)
Recent policy proposals:

WBCSD (Nov. 2006): mid-century global emissions goal
GROCC (Feb. 2007): “ambitious but achievable” midcentury CO2 concentration target

Constraining Rates of Change

Rate of Temperature Change
Different pathways to same long-term
stabilization level imply substantially different
rates of warming in the interim period
Differences in rates of warming are large
enough to be of concern for impacts thatmight be considered “dangerous”
Examples: Thermohaline circulation shutdown,ecosystem impacts.
Source: O’Neill and Oppenheimer, PNAS, 2004.

Illustrative Emissions Pathways
 Peak then decline

pathway for
Kyoto gases

 Non-Kyoto gases

follow medianof SRES scenarios A range ofconcentration
targets achievedin 2050

Source: Wang et al., in prep.

Peak then decline

Constant annual % decline

4.5

0.4

3.0
(deg C/decade)

Temperature Change 2000-2050

Rate of Change vs. 2050 Target

0.3

Climatesensitivity

2.00.2
MedianSRES

0.1

0400

450

500

550

Eqv. CO2, Kyoto gases only, 2050 (ppm)600
Source:Wang et al.

4.50.43.0

Range =(deg C/decade)

Temperature Change 2000-2050

Rate of Change vs. 2050 Target

0.3

430 – 520 ppm

Climatesensitivity

2.00.2
MedianSRES

0.10400450500550

Eqv. CO2, Kyoto gases only, 2050 (ppm)600
Source:Wang et al.

Keeping Long-Term Options
Open:
Exploring AtmosphericPathways

Post-2050 emission decline (%/yr)

Interim Targets and Long-Term
Temperature Change
4.0
Global Average
Temperature
Change, 2200s

3.02.0MedianSRES

1.00400450500550

Eqv. CO2, Kyoto gases only, 2050 (ppm)600
Source:Wang et al.

Post-2050 emission decline (%/yr)

Interim Targets and Long-Term
Temperature Change
4.0

3.0

2.0

MedianSRES

1.00400450500550

Eqv. CO2, Kyoto gases only, 2050 (ppm)600
Source:Wang et al.

Post-2050 emission decline (%/yr)

Interim Targets and Long-Term
Temperature Change
4.0

3.0

2.0

MedianSRES

1.00400450500550

Eqv. CO2, Kyoto gases only, 2050 (ppm)600
Source:Wang et al.

Post-2050 emission decline (%/yr)

Interim Targets and Long-Term
Temperature Change
4.0

3.0

2.0

MedianSRES

1.00400450500550

Eqv. CO2, Kyoto gases only, 2050 (ppm)600
Source:Wang et al.

Post-2050 emission decline (%/yr)

Interim Targets and Long-Term
Temperature Change
4.0

3.0
Upper
Bound

2.0
MedianLower
bound

1.00

400

450500550

Eqv. CO2, Kyoto gases only, 2050 (ppm)

SRES

600
Source:Wang et al.

Post-2050 emission decline (%/yr)

Interim Targets and Long-Term
Temperature Change
4.0
Upper
Bound

3.0
Lower
bound

2.0
MedianSRES
1.00400450500550

Eqv. CO2, Kyoto gases only, 2050 (ppm)600
Source:Wang et al.

Post-2050 emission decline (%/yr)

Interim Targets and Long-Term
Temperature Change
4.0

3.0

2.0MedianSRES
1.00400450500550

Eqv. CO2, Kyoto gases only, 2050 (ppm)600
Source:Wang et al.

Post-2050 emission decline (%/yr)

Interim Targets and Long-Term
Temperature Change
4.0

3.0

2.0MedianSRES
1.00400450500550

Eqv. CO2, Kyoto gases only, 2050 (ppm)600
Source:Wang et al.

Keeping Long-Term Options
Open:
What Kind of Target?

Medium-term Conditions in GGIMitigation Scenarios

IIASA Integrated Assessment Framework

Medium-term Conditions in GGIMitigation Scenarios
1800(b)1600

CO2eq concentration, ppm

1400
1200

A21000
800

B1600
400
20002000

2020
B1B1-480
A2r-970

Source: Keppo et al., TFSC, 2007.

2040
B1-670
A2r
A2r-820

2060

2080
B1-590
A2r-1390
A2r-670

2100
B1-520
A2r-1090

2120

Medium-term Conditions in GGIMitigation Scenarios
Probability of staying below the target

B1r

A2r

100%

80%

3°C
60%

2°C

40%

20%

0%
440

460

480500

520

540

560

580

600

620

CO2 eqivalent concentration (2050)

Source: Keppo et al., TFSC, 2007.

640660680

Medium-term Conditions in GGIMitigation Scenarios
A2r

Probability of staying below the target

B1r
100%

3°C
80%60%

2°C

40%20%

0%
400

420

440

460

480

500

520

CO2 concentration (2050)

Source: Keppo et al., TFSC, 2007.

540560580

Medium-term Conditions in GGIMitigation Scenarios
B1r

Probability of staying below the target

A2r
100%

3°C
80%60%

2°C

40%

20%

2000
0%0%20%40%60%

Share of zero-carbon energy (2050)

Source: Keppo et al., TFSC, 2007.

80%

100%

Conclusions
An interim target could constrain rates of temperature change andpreserve long-term options, serving as a bridge to a longer term
climate goal
Target setting plus regular review could serve as important anchor for
medium-term policy expectations, facilitating long-term investments
A globally-agreed interim target could serve as means of integrating
across a fragmented international policy regime
Useful additional analysis:Implications of different metrics for an interim target: what medium-term
conditions would position us best for the second half of the century?
Costs and political feasibility of different interim targets
Implications of interim targets for shorter-term actions

Mitigation Costs of Interim
Targets:
Research Needs

Costs in GGI Mitigation Scenarios
B1, 3 deg

1

Probability of achieving goalA2, 3 deg
0.8

B1, 2 deg

0.6

0.4

A2, 2 deg
0.2

00.0%

0.5%

1.0%

1.5%

2.0%

2.5%

GDP losses
B1, 2 degrees
A2, 2 degrees

Source: Calculated based on Keppo et al., TFSC, 2007.

B1, 3 degrees
A2, 3 degrees

3.0%

Costs in GGI Mitigation Scenarios
B1, 3 deg

1

Probability of achieving goalA2, 3 deg
0.8

B1, 2 deg

0.670% likelihood
0.4
A2, 2 deg
0.2

00.0%

0.5%

1.0%

1.5%

2.0%

2.5%

GDP losses
B1, 2 degrees
A2, 2 degrees

Source: Calculated based on Keppo et al., TFSC, 2007.

B1, 3 degrees
A2, 3 degrees

3.0%

Costs in GGI Mitigation Scenarios
B1, 3 deg

1

Probability of achieving goalA2, 3 deg
0.8

B1, 2 deg

0.6
70% likelihood
0.4
A2, 2 deg
0.200.0%

0.5%

1.0%

1.5%

2.0%

2.5%

GDP losses
B1, 2 degrees
A2, 2 degrees

Source: Calculated based on Keppo et al., TFSC, 2007.

B1, 3 degrees
A2, 3 degrees

3.0%

Costs of Interim Targets
2.5%

70 % confidence required for reaching the target
2.0%
GDP losses, %A2, 3 deg

1.5%

B1, 2 deg

1.0%

0.5%
B1, 3 deg

0.0%
430

440

450

460

470

480490CO2 concentration in 2050
B1, 2 degrees

B1, 3 degrees

Source: Calculated based on Keppo et al., TFSC, 2007.

A2, 3 degrees

500510Costs of Interim Targets
2.5%

70 % confidence required for reaching the target

GDP losses, %

2.0%

?

A2, 3 deg

1.5%
Hypothetical
InterimTarget

B1, 2 deg

1.0%

How do costs change?
What new information will
be available in 2050?

0.5%
B1, 3 deg
0.0%
430

440

450

460

470

480

490

CO2 concentration in 2050
B1, 2 degrees

B1, 3 degrees

Source: Calculated based on Keppo et al., TFSC, 2007.

A2, 3 degrees

500510