Starting climate policies early in
order to reach long-term
climate targets is...
 as cumbersome
 yet as neccessary
...as getting out of bed early
enough to climb a mountain
following C. Schär (2003)
Where do we want to go?
Malti-gas emission profiles to mitigate dangerous climate
change.
1. Introduction
2. Methods
3. Limitations
4. Results
Malte Meinshausen, [email protected], 17. February 2004, RIVM
Photo courtesy Leila Mead, IISD.ca;
Introduction
 A work-in-progress report
 Objective: Multi-gas emission profiles to limit global mean
temperatures, radiative forcing, CO2 concentrations etc.
 Possible methods for non-CO2:
‚one size fits all‘
scaling to (fossil) CO2
source-specific reduction potentials for all gases
(IMAGE)
cost-optimisations (TIMER/FAIR)
and ...
 The ‘multi-gas meta approach’ motivation:
‘Peaking’ and ‘temperature’ related profiles
Dealing ‘consistently’ with non-CO2 gases
Building on pluralism of existing work to derive a
continuous set of mitigation profiles
Methods I: World per-capita emissions
Methods II: The ‚distribution of possible emission
levels‘
Methods III: Going along equal percentiles
Methods IV: Overview
Limitations
1. Throwing garbage in a blender?
 Underestimation of non-CO2 / landuse
reduction potentials?
Limitations
1. Throwing garbage in a blender?
 Underestimation of non-CO2 / landuse
reduction potentials?
 Comparison with IMAGE EMF21 profiles
shows rough consistency for non-CO2
gases – despite lack of fully elaborated
scenarios in the underlying pool of
scenarios.
2. Or blending everything into garbage?
 Not respecting anti-correlations in
scenarios?
 Ranking correlation analysis
Limitations II: Ranking Correlations
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Limitations
1. Throwing garbage in a blender?
2. Or blending everything into garbage?
 Not respecting anti-correlations in
scenarios?
 Ranking correlation analysis
3. Does the methodology assume a certain
probability of the underlying SRES scenarios?
 Yes, but robust to different probabilities.
Results / ‚Found again‘
 Multi-gas CO2 scenarios have substantially less
overall forcing.  Comparison CO2-only WRE450
and multi-gas S450C.
Results / ‚Found again‘
 Multi-gas CO2 scenarios have substantially less
overall forcing.  Comparison CO2-only WRE450
and multi-gas S450C.
 Under default assumptions, to stay below 2°C
requires, atmospheric concentrations to peak below
420 ppmv CO2 or
490 ppmv CO2 equivalence
Results II: Comparison to long-term pledges
Results II: Comparison to long-term pledges
Results II: Comparison to long-term pledges
Results II: Comparison to long-term pledges
Results II: Comparison to long-term pledges
Results II: Comparison to long-term pledges
Results II: Comparison to long-term pledges
Results II: Comparison to long-term pledges
Results II: Comparison to long-term pledges
Results II: Comparison to long-term pledges
Results II: Comparison to long-term pledges
Results II: Comparison to long-term pledges
Results II: Comparison to long-term pledges
Results / ‚Found again‘
 Multi-gas CO2 scenarios have substantially less
overall forcing.  Comparison CO2-only WRE450
and multi-gas S450C.
 Under default assumptions, to stay below 2°C
requires, atmospheric concentrations to peak below
420 ppmv CO2 or
490 ppmv CO2 equivalence
 Long-term pledges of EU countries roughly
consistent with derived emission reduction
necessities for Annex I countries (Sweden/UK
pledges for 2050 on the higher end, though)
Looking forward to another 3 ½
months here... Thanks!