Time series of annual and 5 year mean surface air (2 m) temperatures for a control
simulation (black) with constant (1870) forcing, and 4 experiments with increasing
greenhouse gases and sulphate aerosols. The observed temperatures since 1850 are shown in
cyan. The first experiment uses observed/reconstructed changes in greenhouse gas and
aerosols (blue). The 3 future scenarios begin in 1980 and specify surface greenhouse gas
concentrations and SO2 fluxes: for a "business as
usual" scenario (red); a policy limited scenario (green), stabilizing at 550 ppmv of CO2 after year 2100; and the IPCC SRES scenario A1 (magenta).