Climate scientists tend not to report climate results in whole temperatures. Instead, they talk about how the annual temperature departs from an average, or baseline. They call these departures "anomalies
." They do this because temperature anomalies are more consistent in an area than absolute temperatures are. For example, the absolute temperature atop the Empire State Building may be different by several degrees than the absolute temperature at New York’s LaGuardia Airport. But the differences from their own averages are likely to be about the same. It means that scientists can get a better idea about temperature with fewer monitoring stations. That’s particularly useful in places where measurement is very difficult (ie, deserts).
The simulation results are aligned to the observations using the 1880-1910 average. What's most important about these temperatures are the trends—the shape and trajectory of the line, and not any single year’s temperature.