The graphs and maps all show changes relative to average temperatures for the three decades from 1951 to 1980, the earliest period for which there was sufficiently good coverage for comparison. This gives a consistent view of climate change across the globe. To put these numbers in context, the NASA team estimates that the global average temperature for the 1951-1980 baseline period was about 14 °C.
The more red an area the greater the increase was estimated to be, relative to estimates for 1951 to 1980 (especially noticeable in the Northern Hemisphere).
The most interesting part is when you compare all the way back to to the 19th century when it was much cooler. You can also click on locations for a time series of five-year averages. [Thanks, Peter]