solar geoengineering versus mitigation: the role …...solar geoengineering versus mitigation: the...
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Solar Geoengineering versus Mitigation:The Role of Time Preference
Mariia Belaia, David Keith, Gernot WagnerWork in progress
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Anthropogenic Climate Change: Market Failure
Figure 1: Direct measurements
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Anthropogenic Climate Change: Market Failure
Figure 2: Proxy measurements: reconstruction from ice cores
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Climatic Risk
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Climatic Risk
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Climatic Risk
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Yet ...
1. Climate inertia
2. Socio-economic inertia
3. Technological inertia
4. Population growth, increasing energy demand
5. Limits to adaptation
6. Tragedy of global commons
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Geoengineering
Ultimate goal: reduce negative impacts of climate change.
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Geoengineering
• Carbon dioxide removal (CDR)
• Solar radiation management (SRM)
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SRM: Stratospheric aerosols injection
Figure 3
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The DICE-SRM model:
The DICE-2016 model extended to include SG and uncertainty in climatechange:
• 5- to 1-year timestep.
• SRM enters via radiative forcing changes and damage costs from theSRM side-effects.
• Uncertainty in climate sensitivity.
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The DICE-SRM model
Economy:
W =T∑t=1
1
(1 + ρ)tU(c(t))L(t) (1)
U(c) =c1−η − 1
1− η(2)
Y grosst = AtK
γt L
1−γt (3)
Y nett =
1
1 + Ωt· Y gross
t (4)
Yt = (1− Λt)Ynett (5)
Λt = θt,1µθ2 (6)
Ct = Yt − It (7)
ct =Ct
Lt(8)
It = st · Yt (9)
Kt+1 = It + (1− δK )Kt (10)
0 ≤ µ ≤ 1 is emissions control rate.11 / 23
The DICE-SRM model:
Emissions:
E indt = σt [1− µt ]Y
grosst (11)
Et = E indt + E land
t (12)
Carbon cycle (three-reservoir model):
Matt = b11M
att−1 + b12M
upt−1 + Et (13)
Mupt = b21M
att−1 + b22M
upt−1 + b23M
lot−1 (14)
M lot = b31M
lot−1 + b32M
upt−1 (15)
Radiative Forcing:
Ft = η(log2(Mat
t
Mat1750
)) + F ext − FG
t (16)
Climate Model:
T att = T at
t−1 + ψ1[Ft − ψ2Tatt−1 − ψ3(T at
t−1 − T lot−1)] (17)
T lot = T lo
t−1 + ψ4(T att−1 − T lo
t−1) (18)
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The DICE-SRM model
Damages costs (fraction of gross world product):
Dt = α1Tatt + α2(T at
t )2 + DGt (19)
DGt = β| FG
t
F 2xCO2t
| (20)
Figure 4: Function DG
Calibration:13 / 23
Integrated Assessment Model of Climate and Economy
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I. No Climate Policy
(a)
(c)
(b)
(d)15 / 23
II. Optimal control. DICE-SRM (–) vs DICE (–)
(a)
(c)
(b) DICE-SRM
(d)16 / 23
Higher ρ: 1.5% (–) vs 3% (–)
(a) (b)
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Lower ρ: 1.5% (–) vs 0.1% (–)
(a) (b)
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Higher η: 1.45 (–) vs 2 (–)
(a) (b)
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Social Cost of Carbon
Calibration Model ρ, % η SCC (2020) 2010 USDDefault DICE 1.5 1.45 37.64
DICE-SRM 1.5 1.45 32.18Higher ρ DICE, 3 1.45 15.31
DICE-SRM 3 1.45 14.94Lower ρ DICE 1 1.45 57.57
DICE-SRM 1 1.45 45.52Very low ρ DICE 0.1 1.45 178.84
DICE-SRM 0.1 1.45 133.95Higher η DICE 1.5 2 20.45
DICE-SRM 1.5 2 19.04
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III. Climate Change Uncertainty
Figure 5: DICE-SRM
Figure 6: equilibrium climate sensitivity probability density function
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Expected Utility Framework.
DICE-SRM (–) vs DICE (–)
(a) (b)
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Lower ρ: 1.5% (–) vs 0.1% (–)
(a) (b)
Figure 7
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Solar Radiation Management versus Mitigation
Summary from DICE-SRM:• SRM reduces SCC.• SRM reduces radiative forcing during the period around the peak of
industrial emissions.• SRM reduces the rate of optimal emissions control rate, thus
potentially addressing the question of limited speed of success inemissions reduction.
• Higher the discount rate, further both mitigation and SRM aredelayed.
• Under climate change uncertainty: lower PRTP =⇒ strongerabatement and early and moderate SRM. Otherwise, strong and lateSRM.
Next steps:• Introduce CDR.• Optimal CDR-SRM-mitigation portfolio analyzes for alternative
preference specifications.• Sensitivity with respect to damage costs, CDR costs, and SRM
side-effects.• Explore Epstein-Zin utility (further).
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