Page 87 - Climate Change and Food Systems

chapter 3: economic modelling of climate impacts and adaptation in agriculture: a survey of methods, results and gaps
table 1
SRES Scenarios
World
A1 STORYLINE
Market-oriented
ECONOMIC EMPHASIS
World
A2 STORYLINE
Differentiated
Economy
Fastest per capita growth
Economy
Regionally oriented; lowest per capita growth
Population
2050 peak, then decline resouces
Governance
Strong regional interactions; income convergence
Population
Continuously increasing
Self reliance with preservation of local identities
Technology
3 scenario groups
Governance
A1F1
World
Economy
Governance
Fossil-intensive
Convergent
Clean and resource efficient
Technology
World
Population
Governance
Slowest and most fragmented development
A1T
non-fossil energy
A1B
Balanced across all sources
B1 STORYLINE
B2 STORYLINE
Local solutions
Service and information based, lower growth than A1
Economy
Intermediate growth
Continuously increasing at lower rate than A2
Population
Same as A1
Global solutions to economic, social and environmental sustainability
Local and regional solutions to environmental protection and social equity
Technology
Technology
More rapid than A1; less rapid and more diverse than A1/B1
ENVIRONMENTAL EMPHASIS
of the A1 story line, were used as inputs into six independent integrated assessment models (IAMs), which quantified their projected effects on GHG emissions, yielding a total of 40 emission scenarios (Figure 2). The use of a range of emission scenarios as inputs into the GCMs addresses the uncertainties about future emission levels due to gaps in current scientific knowledge and to the unpredictability of future human behaviour. There is no probability assigned to the likelihood of any of their occurrences, nor any judgment made about their relative desireability. There is some overlap in the emission levels across the Special Report on
Emissions Scenarios (SRES) due to commonalities in their underlying story lines, but they increasingly diverge over time. Therefore, the longer the time horizon of an economic assessment, the more sensitive are its results to the selection of an SRES.
Climate projections from the same emission scenario can differ across GCMs because
of differences in the models’ structures and parameter values. The IPCC reports both the mean and the range of the climate projections for each SRES from all participating CMIP3 GCM models, with all models’ results given equal weight. The range of model results is useful for illustrating the
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REGIONAL EMPHASIS
GLOBAL INTEGRATION