Global Temperature Update Through 2012 by J. Hansen, M. Sato, R. Ruedy (Jan 15 2013)
Global surface temperature in 2012 was +0.56°C (1°F) warmer than the 1951-1980 base period average, despite much of the year being affected by a strong La Nina. Global temperature thus continues at a high level that is sufficient to cause a substantial increase in the frequency of extreme warm anomalies. The 5-year mean global temperature has been flat for a decade, which we interpret as a combination of natural variability and a slowdown in the growth rate of the net climate forcing.
Frequency of occurrence of local June-July-August temperature anomalies (relative to 1951-1980 mean) for Northern Hemisphere land in units of local standard deviation (horizontal axis). Temperature anomalies in 1951-1980 match closely the normal distribution (green curve), which is used to define cold (blue), typical (white) and hot (red) seasons, each with probability 33.3%. Lower graphs use only a subset of stations (1886 of 6147) that were present throughout recent decades as well as the base period.