Workshop Report - IPCC

Annex I: Paper
Conducting this experiment using several reference scenarios or different models provides a sensitivity analysis of
how robust the policy is to different reference world evolutions.
What is the effect of future socioeconomic conditions on the impacts of a certain degree of climate change?
The presence of several different SSPs allows one to explore the consequences of different SSPs on climate
impacts, but also on the effectiveness of climate policy.
Socio‐economic reference pathway
SSP1 SSP2 SSP3 …
Forcing level (W/m 2 )
8.5
6.0
4.5
2.6
Figure 2.6: Comparing results along one row of the scenario matrix show how mitigation, adaption, and
remaining climate impacts play out under different socioeconomic futures.
Figure 2.7 summarizes the two dimensions of climate change and climate policy analysis using the scenario
matrix approach. The range of radiative forcings in the reference case will vary with SSP, and there may be SSPs
for which very high forcings such as RCP8.5 will not be obtained even in the reference case. Similarly, the
challenges to mitigation and adaptation will vary with SSP, so that different levels of mitigation costs,
adaptation effectiveness, and residual climate damages will be obtained for a given RCP level in different SSPs.
These effects can be explored by a comparison of studies bridging different cells across the columns and rows of
the matrix. A fully integrated analysis of impacts, adaptation, vulnerability, and mitigation would include
feedbacks to the initial (exogenous) boundary conditions presented by the SSP. For example, it may be the case
that impacts, adaptation, and mitigation reduce (or increase) GDP or alter population movements, initially
assumed exogenous for all cells in a column. The “output” GDP or population distribution would then be
different for each cell in a column (because the climate change is different and climate policies have been
introduced).
It should be noted that it seems preferable to include 3.7 W/m 2 in a set of preferred scenarios because this
forcing level is an important part of ongoing policy-making activities. Analyses of the mitigation and adaptation
implication of this forcing level could be informative for policy-makers.
Workshop on Socio-Economic Scenarios - 16