32
A1.
Rapid economic and population growth
that peaks mid-century. Emphasis on
fossil (A1F), non-fossil (A1T) or balance of
energy sources (A1B).
A2.
Heterogeneous world, with strong self -
reliance and local identity. Continuously
increasing population. Fragmented
economic development.
B2.
Local solutions to sustainability issues.
Continuously increasing population, but
slower than A2. Slower and more diverse
technological change.
B1.
Population as A1. Economy changes to
services, information and clean
technology and has low material intensity.
Global solutions to global change issues.
Variability in projections of future climate that are available from these web sites reflects several important
influences, as follows:
x
Greenhouse gas emissions scenario – climate change projections for the IPCC’s
Fourth Assessment
Report
were based on the so-called SRES scenarios (IPCC, 2000;
Figure 4.11
). These scenarios
provide a narrative of future change in the global economy and society and a trajectory for future
greenhouse gas emissions. There are 40 different scenarios, although only a few are commonly used
in modelling studies. GCM outputs available from
are framed
around low (B1), medium (A1B) and high (A1FI) emissions scenarios. Global temperatures are
projected to increase more rapidly and to a greater extent under the higher emissions scenarios.
x
Sensitivity of the global climate system to increased greenhouse gas concentrations – GCMs may
exhibit a range of sensitivities of global climate to increasing greenhouse gas emissions, with greater
sensitivity resulting in a more rapid increase in temperature per unit increase in greenhouse gas
concentrations.
x
GCM representation of the global climate system – the various climate models include differing
mathematical representations of the global climate system and may produce quite different results for
the same timeframe, emissions scenario and climate sensitivity. Data available from
represent this variability by providing the 10
th
, 50
th
and 90
th
percentile results from the full ensemble of models for which data are available.
Figure 4.11: Overview of IPCC SRES scenarios: global change and emissions scenarios used in climate
modelling
Source: Derived from IPCC (2000)
Model outputs are reported as an amount or percentage of change in a particular climate variable for a
given time, emissions scenario and model. They represent change from a baseline or reference period,
which is typically 1980-1999. Climate change factors are typically the average change from the reference
period over a 20 year period that is centred on the reported day. They are used to adjust or perturb an
historical sequence of climate variables over the reference period to develop a climate change profile or
new climate sequence.
