allowable carbon emissions lowered by multiple climate targets · 2015. 1. 20. · fortunat joos,...
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Allowable carbon emissions lowered by multiple climate targets
Thomas Stocker Climate and Environmental Physics Physics Institute, University of Bern Switzerland
7th Annual Meeting IAMC Meeting, University of Maryland
Collaborators:
Fortunat Joos, Patrik Pfister, Marco Steinacher
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Allowable carbon emissions lowered by multiple climate targets
7th Annual Meeting IAMC Meeting, University of Maryland
1. Cumulative carbon emissions and the 2°C target
2. Combining climate system targets
3. Mitigation delay sensitivity
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Limiting climate change will require substantial and sustained reductions of
greenhouse gas emissions.
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Limiting climate change would require substantial and sustained reductions of
greenhouse gas emissions, which
together with adaptation, can limit climate change risks.
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IPC
C 2
013,
Fig
. SP
M.1
0
790 GtC
2°C
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Allowable carbon emissions lowered by multiple climate targets
7th Annual Meeting IAMC Meeting, University of Maryland
1. Cumulative carbon emissions and the 2°C target
2. Combining climate system targets
3. Mitigation delay sensitivity
![Page 7: Allowable carbon emissions lowered by multiple climate targets · 2015. 1. 20. · Fortunat Joos, Patrik Pfister, Marco Steinacher . Allowable carbon emissions lowered by multiple](https://reader035.vdocuments.net/reader035/viewer/2022071415/610fe048f92e88792373ca6a/html5/thumbnails/7.jpg)
(Steinacher et al., 2013)
UNFCCC Article 2 requires more than one climate target
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(Ste
inac
her e
t al.,
201
3)
• Bayesian approach of model
calibration
• definition of climate targets
of comparable stringency
• probabilistic determination
of climate system reponse
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chance < 5% that ΔT < 3oC
chance > 95% that ΔT < 3oC
chance = 66% that ΔT < 3oC
CO2 Concentration by 2100 (ppm)
(Ste
inac
her e
t al.,
201
3)
Climate target: Surface air temperature
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chance = 66% that OA < 90%
CO2 Concentration by 2100 (ppm)
(Ste
inac
her e
t al.,
201
3)
Climate target: Ocean acidification (loss of saturated waters)
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Temperature target (3oC)
Most stringent single target
Multiple targets
(Steinacher et al., 2013)
From single to multiple climate targets
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(Steinacher et al., 2013)
Allowable emission budget for multiple climate targets
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Allowable carbon emissions lowered by multiple climate targets
7th Annual Meeting IAMC Meeting, University of Maryland
1. Cumulative carbon emissions and the 2°C target
2. Combining climate system targets
3. Mitigation delay sensitivity
![Page 14: Allowable carbon emissions lowered by multiple climate targets · 2015. 1. 20. · Fortunat Joos, Patrik Pfister, Marco Steinacher . Allowable carbon emissions lowered by multiple](https://reader035.vdocuments.net/reader035/viewer/2022071415/610fe048f92e88792373ca6a/html5/thumbnails/14.jpg)
2040
2020
2030
Academic scenarios to reach the 2°C target
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Clim
ate
Targ
et (°
C)
Starting Year of Emissions Reduction
The closing door of climate targets
(Sto
cker
, 201
3)
Unachievable Climate Targets
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Clim
ate
Targ
et (°
C)
Starting Year of Emissions Reduction
(Sto
cker
, 201
3, A
llen
& S
tock
er, 2
014)
Mitigation delay: Peak temperature rises fast
Warming during delay
Delay in mitigation
Mitigation delay sensitivity ΔT/ Δt
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Mitigation delay sensitivity in the Bern3D model
(Pfis
ter a
nd S
tock
er, 2
014,
in p
rep.
)
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Mitigation delay sensitivity in the Bern3D model
(Pfis
ter a
nd S
tock
er, 2
014,
in p
rep.
)
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Mitigation delay sensitivity in the Bern3D model
(Pfis
ter a
nd S
tock
er, 2
014,
in p
rep.
)
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Mitigation delay: Peak temperature rises fast
20th century warming: ≈ 0.08 °C per decade
1998 to 2012 warming: ≈ 0.05 °C per decade
Mitigation Delay Sensitivity
≈ 0.4 °C per decade
Committed peak warming rises 3 to 8 times faster than observed warming
1951 to 2012 warming: ≈ 0.12 °C per decade
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Conclusions:
7th Annual Meeting IAMC Meeting, University of Maryland
v 2°C target remains a powerful target because many (but not all) climate changes scale with ΔT.
v However, the 2°C target does not capture all Reasons For Concern: e.g., ocean acidification, sea level rise, ...
v Multiple targets require even deeper emission cuts.
v Mitigation Delay Sensitivity (MDS) is a new policy-relevant metric: MDS(T) rises as fast as CO2 emissions.