SODBatch A&B SPM Comments co-chair response final ... - ipcc-wg3

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IPCC WGIII Fourth Assessment Report, Second Order Draft
125 agreement, but another issue seems relevant here: several non-CO2
emission reduction options exist in the short term at lower cost
compared to CO2. But reducing to very low levels in the long term
(e.g. 450 co2eq.) non-CO2 options are no longer available and CO2
is reduced more compared to non-CO2. This is important to show
that non-CO2 options can complement but not replace CO2
mitigation.
SPM-
593
7
F
5
(Government of European Community / European Commission)
A 8 10 19 15 Figure SPM.5 in the summary for policymaker is crucial.
Therefore, one needs to be very careful what kind of numbers and
model results can and should be shown. The graph shows GDP
losses with different stabilisation targets. This figure as it is
constructed now is as if you would compare apples and oranges.
The graph is misleading and gives wrong impressions. model
results cannot be compared because of the following reasons: 1.
different baseline assumptions: IMCP focuses on technological
changes which is relevant also for the baseline (TC in baseline),
IPCC not. 2. different model parameter assumptions: not only for
the baseline, but also for substitution elasticities etc.; 3. different
model types: top down models and bottom up models usually show
very different results, especially because they differ in type,
assumptions and TC; 4.different regional scale of models: in IMCP
there are some one region -models (Demeter, Mind) which can
hardly compared with the other multi regional models;. as this slide
with be used as policy recommendation, it is dangerous to present
such kind of overview. As the IMCP study focuses primarily on
TC, "benefits" of emissions mitigation as presented by the E3ME
model, can only be explained by TCs. It is however, difficult to
explain decision maker, why emissions mitigation improves GDP.
This is not in line with any IPCC study before; furthermore, it is
very confusing to have two AIM studies- AIM A1 PS and AIM-
IMCP show very different results: this can be explained, as before,
through the treatment of TC in IMCP. It is however very difficult to
explain outsiders why this is the case. I would strongly recommend
Expert Review of Second-Order-Draft
Confidential, Do Not Cite or Quote
Response suggested by cochairs
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DISCUSS 3 Accepted.
Figure to be
revised
(3)
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