Figure 6. Northern hemisphere (NH) temperature histories. Comparison of multiproxy reconstructions of the NH annual mean temperature (1-3) with model simulations (9, 17-19). Gerber I, 1.5°C for CO2 doubling; Gerber II, 2.5°C for CO2 doubling. Also shown is a reconstruction of summer extratropical continental NH temperatures (5). All reconstructions have been scaled to the NH instrumental record (20) over the 1856 to 1980 period and have been smoothed on time scales of >40 years to highlight the long-term variations. Source: Mann, 2002.