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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).