Global Temperature Trends: 2008 Annual Summation

by James Hansen, Makiko Sato, Reto Ruedy, Ken Lo

The Goddard Institute for Space Studies has analyzed the global temperature trends based on 2008 surface air temperature leading to the conclusion that, despite the cold brought on by the strong La Nina event last year, 2008 was the ninth warmest year since measurements began in 1880.

Calendar year 2008 was the coolest year since 2000, according to the Goddard Institute for Space Studies analysis [Reference 1] of surface air temperature measurements (Figure 1, below). In our analysis 2008 is the ninth warmest year in the period of instrumental measurements, which extends back to 1880. The ten warmest years all occur within the 12-year period 1997-2008. The two standard deviation (95 percent confidence) uncertainty in comparing recent years is estimated as 0.05°C [Reference 2], so we can only conclude with confidence that 2008 was somewhere within the range from 7th to 10th warmest year in the record.

The map of global temperature anomalies in 2008, Figure 1 (right), shows that most of the world was either near normal or warmer than in the base period (1951-1980). Eurasia, the Arctic and the Antarctic Peninsula were exceptionally warm, while much of the Pacific Ocean was cooler than the long-term average. The relatively low temperature in the tropical Pacific was due to a strong La Nina that existed in the first half of the year. La Nina and El Nino are opposite phases of a natural oscillation of tropical temperatures, La Nina being the cool phase

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