This is seen more clearly in Figure 3
, which shows the decadal change in simulated (average of all models) and observed temperature. This graph shows that the models in general performed well from the mid-1970s to the end of the century, when they were simulating the increase in temperatures due to CO2, but less well at other times. In particular:
- The observed natural rate of increase from 1910 to 1940 averaged 0.151 C/decade but the rate simulated by the models was 0.037 C/decade
- The two periods of natural cooling, at the start and middle of the 20th century, were not represented in the simulated temperatures. A similar observation appears to be true in relation to the start of the 21st century when the models projected a steady increase but observed values have not shown such a trend.