요약

The results presented in this chapter are based on simulations

made with global climate models and apply to spacial scales of

hundreds of kilometres and larger. Chapter 10 presents results for

regional models which operate on smaller spatial scales. Climate

change simulations are assessed for the period 1990 to 2100 and

are based on a range of scenarios for projected changes in

greenhouse gas concentrations and sulphate aerosol loadings

(direct effect). A few Atmosphere-Ocean General Circulation

Model (AOGCM) simulations include the effects of ozone and/or

indirect effects of aerosols (see Table 9.1 for details). Most

integrations1 do not include the less dominant or less well

understood forcings such as land-use changes, mineral dust,

black carbon, etc. (see Chapter 6). No AOGCM simulations

include estimates of future changes in solar forcing or in volcanic

aerosol concentrations.

There are many more AOGCM projections of future climate

available than was the case for the IPCC Second Assessment

Report (IPCC, 1996) (hereafter SAR). We concentrate on the

IS92a and draft SRES A2 and B2 scenarios. Some indication of

uncertainty in the projections can be obtained by comparing the

responses among models. The range and ensemble standard

deviation are used as a measure of uncertainty in modelled

response. The simulations are a combination of a forced climate

change component together with internally generated natural

variability. A number of modelling groups have produced

ensembles of simulations where the projected forcing is the same

but where variations in initial conditions result in different

evolutions of the natural variability. Averaging these integrations

preserves the forced climate change signal while averaging out the

natural variability noise, and so gives a better estimate of the

models’' projected climate change.