text: What the researchers found was that the observed temperature trends calculated from periods ranging from 10 to 32 years all lie below the average trend of the same length projected by a large family of climate models (Fig. 2). Each climate model includes some representation of some of the processes which lead to ?natural? (random) variability (processes such as El Nio/La Nia, volcanic eruptions, solar variability?note that not all models include all of these processes throughout the entire 1979-2010 period of study). As the time period over which the temperature trend is calculated increases, the impact of natural variability on the magnitude (and even the sign) of the trend decreases as the short-term temperature deviations caused by random variability tend to cancel out.